Loeb, Norman G.; Doelling, David R.; Kato, Seiji; Su, Wenying; Mlynczak, Pamela E.; Wilkins, Joshua C.Loeb, N. G., D. R. Doelling, S. Kato, W. Su, P. E. Mlynczak, J. C. Wilkins, 2024: Continuity in Top-of-Atmosphere Earth Radiation Budget Observations. doi: 10.1175/JCLI-D-24-0180.1. The Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) product combines CERES and Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua satellites to create a record of Earth’s Radiation Budget (ERB) and the associated cloud properties. As the Terra and Aqua orbits are no longer maintained at a fixed mean local time, EBAF recently transitioned to the CERES and Visible Infrared Imaging Radiometer Suite (VIIRS) instruments on NOAA-20 to avoid introducing a time-dependent bias in the record. To ensure smooth transitions between the Terra, combined Terra and Aqua (Terra+Aqua), and NOAA-20 portions of the record, regional climatological adjustments derived from the overlap period between missions are applied to anchor the entire record to Terra+Aqua. We estimate the random error in global monthly anomalies following the transitions to be
Lyapustin, Alexei; Wang, Yujie; Choi, Myungje; Xiong, Xiaoxiong; Angal, Amit; Wu, Aisheng; Doelling, David R.; Bhatt, Rajendra; Go, Sujung; Korkin, Sergey; Franz, Bryan; Meister, Gerhardt; Sayer, Andrew M.; Roman, Miguel; Holz, Robert E.; Meyer, Kerry; Gleason, James; Levy, RobertLyapustin, A., Y. Wang, M. Choi, X. Xiong, A. Angal, A. Wu, D. R. Doelling, R. Bhatt, S. Go, S. Korkin, B. Franz, G. Meister, A. M. Sayer, M. Roman, R. E. Holz, K. Meyer, J. Gleason, R. Levy, 2023: Calibration of the SNPP and NOAA 20 VIIRS sensors for continuity of the MODIS climate data records. Remote Sensing of Environment, 295, 113717. doi: 10.1016/j.rse.2023.113717. Accurate long-term sensor calibration and periodic re-processing to ensure consistency and continuity of atmospheric, land and ocean geophysical retrievals from space within the mission period and across different missions is a major requirement of climate data records. In this work, we applied the Multi-Angle Implementation of Atmospheric Correction (MAIAC)-based vicarious calibration technique over Libya-4 desert site to perform calibration analysis of Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi National Polar-orbiting Partnership (SNPP) and NOAA-20 satellites. For both VIIRS sensors we characterized residual linear calibration trends and cross-calibrated both sensors to MODerate resolution Imaging Spectroradiometer (MODIS) Aqua regarded as a calibration standard. The relative spectral response (RSR) differences were accounted for using the German Aerospace Center (DLR) Earth Sensing Imaging Spectrometer (DESIS) hyperspectral surface reflectance data. Our results agree with independent vicarious calibration results of both the MODIS/VIIRS Characterization Support Team as well as the CERES Imager and Geostationary Calibration Group within estimated uncertainty of 1–2%. Analysis of MAIAC geophysical products with the new calibration shows a high level of agreement of MAIAC aerosol, surface reflectance and NDVI records between MODIS and VIIRS. Excluding high aerosol optical depth (AOD), all three sensors agree in AOD with mean difference (MD) less than 0.01 and residual mean squared difference rmsd ∼ 0.04. Spectral geometrically normalized surface reflectance agrees within rmsd of 0.003–0.005 in the visible and 0.01–0.012 at longer wavelengths. The residual surface reflectance differences are fully explained by differences in spectral filter functions. Finally, difference in NDVI is characterized by rmsd ∼ 0.02 and MD less than 0.003 for NDVI based on VIIRS imagery bands I1/I2 and less than 0.01 for NDVI based on VIIRS radiometric bands M5/M7. In practical sense, these numbers indicate consistency and continuity in MAIAC records ensuring the smooth transition from MODIS to VIIRS. Calibration; MODIS; VIIRS; NDVI; MAIAC; Surface reflectance
Doelling, David R.; Haney, Conor; Bhatt, Rajendra; Scarino, Benjamin; Gopalan, ArunDoelling, D. R., C. Haney, R. Bhatt, B. Scarino, A. Gopalan, 2022: Daily monitoring algorithms to detect geostationary imager visible radiance anomalies. Journal of Applied Remote Sensing, 16(1), 014502. doi: 10.1117/1.JRS.16.014502. The NASA Clouds and the Earth’s Radiant Energy System (CERES) project provides observed flux and cloud products for the climate science community. Geostationary satellite (GEO) imager measured clouds and broadband derived fluxes are incorporated in the CERES SYN1deg product to provide regional diurnal information in between Sun-synchronous Terra and Aqua CERES measurements. The recently launched GEO imagers with onboard calibration systems have active calibration teams that incrementally update the calibration in order to mitigate calibration drifts. However, short-term L1B radiance anomalies and calibration adjustment discontinuities may still exist in the record. To avoid any GEO cloud and flux artifacts in the CERES SYN1deg product, these calibration events must be addressed while scaling the GEO imagers to the Aqua-moderate resolution imaging spectroradiometer (MODIS) calibration reference. All-sky tropical ocean ray-matching (ATO-RM) and deep convective cloud invariant target (DCC-IT)-based monitoring algorithms are presented to detect calibration-driven daily anomalies in the GOES-16 Advanced Baseline Imager L1B visible (0.65 μm) radiance measurements. Sufficient daily ATO-RM sampling was obtained both by ray-matching GOES-16 with multiple MODIS and visible-infrared imaging radiometer suite imagers as well as by increasing the grid resolution. Optimized angular matching and outlier filtering were most effective in reducing the ATO-RM daily gain algorithm noise. The DCC-IT daily calibration algorithm utilized a larger domain and included more GOES-16 scan times. The DCC-IT daily gain uncertainty was reduced by normalizing the DCC regional reflectance on a regional, seasonal, and diurnal basis. The combination of ATO-RM and DCC-IT daily monitoring algorithms is shown to detect, with a high degree of confidence, daily GOES-16 L1B calibration-driven radiance anomalies >2.4 % , while keeping false positives at a minimum. Remarkably, the ATO-RM and DCC-IT daily gains are mostly within 0.5%. The ATO-RM and DCC-IT daily monitoring algorithms can be easily adapted to other GEO imagers and visible channels.
Scott, Ryan C.; Rose, Fred G.; Stackhouse, Paul W.; Loeb, Norman G.; Kato, Seiji; Doelling, David R.; Rutan, David A.; Taylor, Patrick C.; Smith, William L.Scott, R. C., F. G. Rose, P. W. Stackhouse, N. G. Loeb, S. Kato, D. R. Doelling, D. A. Rutan, P. C. Taylor, W. L. Smith, 2022: Clouds and the Earth’s Radiant Energy System (CERES) Cloud Radiative Swath (CRS) Edition 4 Data Product. J. Atmos. Oceanic Technol., 39(11), 1781-1797. doi: 10.1175/JTECH-D-22-0021.1. Abstract Satellite observations from Clouds and the Earth’s Radiant Energy System (CERES) radiometers have produced over two decades of world-class data documenting time–space variations in Earth’s top-of-atmosphere (TOA) radiation budget. In addition to energy exchanges among Earth and space, climate studies require accurate information on radiant energy exchanges at the surface and within the atmosphere. The CERES Cloud Radiative Swath (CRS) data product extends the standard Single Scanner Footprint (SSF) data product by calculating a suite of radiative fluxes from the surface to TOA at the instantaneous CERES footprint scale using the NASA Langley Fu–Liou radiative transfer model. Here, we describe the CRS flux algorithm and evaluate its performance against a network of ground-based measurements and CERES TOA observations. CRS all-sky downwelling broadband fluxes show significant improvements in surface validation statistics relative to the parameterized fluxes on the SSF product, including a ∼30%–40% (∼20%) reduction in SW↓ (LW↓) root-mean-square error (RMSΔ), improved correlation coefficients, and the lowest SW↓ bias over most surface types. RMSΔ and correlation statistics improve over five different surface types under both overcast and clear-sky conditions. The global mean computed TOA outgoing LW radiation (OLR) remains within
Sun, Moguo; Doelling, David R.; Loeb, Norman G.; Scott, Ryan C.; Wilkins, Joshua; Nguyen, Le Trang; Mlynczak, PamelaSun, M., D. R. Doelling, N. G. Loeb, R. C. Scott, J. Wilkins, L. T. Nguyen, P. Mlynczak, 2022: Clouds and the Earth’s Radiant Energy System (CERES) FluxByCldTyp Edition 4 Data Product. J. Atmos. Oceanic Technol., 39(3), 303-318. doi: 10.1175/JTECH-D-21-0029.1. Abstract The Clouds and the Earth’s Radiant Energy System (CERES) project has provided the climate community 20 years of globally observed top of the atmosphere (TOA) fluxes critical for climate and cloud feedback studies. The CERES Flux By Cloud Type (FBCT) product contains radiative fluxes by cloud type, which can provide more stringent constraints when validating models and also reveal more insight into the interactions between clouds and climate. The FBCT product provides 1° regional daily and monthly shortwave (SW) and longwave (LW) cloud-type fluxes and cloud properties sorted by seven pressure layers and six optical depth bins. Historically, cloud-type fluxes have been computed using radiative transfer models based on observed cloud properties. Instead of relying on radiative transfer models, the FBCT product utilizes Moderate Resolution Imaging Spectroradiometer (MODIS) radiances partitioned by cloud type within a CERES footprint to estimate the cloud-type broadband fluxes. The MODIS multichannel derived broadband fluxes were compared with the CERES observed footprint fluxes and were found to be within 1% and 2.5% for LW and SW, respectively, as well as being mostly free of cloud property dependencies. These biases are mitigated by constraining the cloud-type fluxes within each footprint with the CERES Single Scanner Footprint (SSF) observed flux. The FBCT all-sky and clear-sky monthly averaged fluxes were found to be consistent with the CERES SSF1deg product. Several examples of FBCT data are presented to highlight its utility for scientific applications.
Bhatt, Rajendra; Doelling, David R.; Coddington, Odele; Scarino, Benjamin; Gopalan, Arun; Haney, ConorBhatt, R., D. R. Doelling, O. Coddington, B. Scarino, A. Gopalan, C. Haney, 2021: Quantifying the Impact of Solar Spectra on the Inter-Calibration of Satellite Instruments. Remote Sensing, 13(8), 1438. doi: 10.3390/rs13081438. In satellite-based remote sensing applications, the conversion of the sensor recorded top-of-atmosphere reflectance to radiance, or vice-versa, is carried out using a reference spectral solar irradiance (SSI) dataset. The choice of reference SSI spectrum has consistently changed over the past four decades with the increasing availability of more accurate SSI measurements with greater spectral coverage. Considerable differences (up to 15% at certain wavelengths) exist between the numerous SSI spectra that are currently being used in satellite ground processing systems. The aim of this study is to quantify the absolute differences between the most commonly used SSI datasets and investigate their impact in satellite inter-calibration and environmental retrievals. It was noted that if analogous SNPP and NOAA-20 VIIRS channel reflectances were perfectly inter-calibrated, the derived channel radiances can still differ by up to 3% due to the utilization of differing SSI datasets by the two VIIRS instruments. This paper also highlights a TSIS-1 SIM-based Hybrid Solar Reference Spectrum (HSRS) with an unprecedented absolute accuracy of 0.3% between 460 and 2365 nm, and recommends that the remote sensing community use it as a common reference SSI in satellite retrievals. calibration; solar spectra; VIIRS; solar constant; TSIS-1 SIM
Doelling, David R.; Cao, Changyong; Xiong, JDoelling, D. R., C. Cao, J. Xiong, 2021: GSICS recommends NOAA-20 VIIRS as reflective solar band (RSB) calibration reference. GSICS Quarterly Vol. 14 No. 4, 14(4), 2-4. doi: 10.25923/JMBT-D994.
Bhatt, Rajendra; Doelling, David R.; Angal, Amit; Xiong, Xiaoxiong; Haney, Conor; Scarino, Benjamin R.; Wu, Aisheng; Gopalan, ArunBhatt, R., D. R. Doelling, A. Angal, X. Xiong, C. Haney, B. R. Scarino, A. Wu, A. Gopalan, 2020: Response Versus Scan-Angle Assessment of MODIS Reflective Solar Bands in Collection 6.1 Calibration. IEEE Transactions on Geoscience and Remote Sensing, 58(4), 2276-2289. doi: 10.1109/TGRS.2019.2946963. The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments onboard the Aqua and Terra satellites have been operated for nearly two decades, producing high-quality earth observation data sets suitable for a broad range of scientific studies regarding the earth's land, ocean, and atmospheric processes. The high radiometric accuracy of MODIS reflective solar band (RSB) calibration has also served as benchmark measurements for on-orbit cross-calibration studies. As the two MODIS instruments have operated well beyond their design lifespan of six years, the measurements from the onboard calibrators alone become inadequate to characterize the sensor's response at all scan angles, as evinced by long-term drifts observed at certain scan positions of the Aqua-MODIS 0.64- and 0.86-μm bands in Collection 6 (C6) data set. The latest MODIS Level 1B C6.1 data set incorporates earth-view response trending from invariant desert sites as supplemental inputs to characterize the scan-angle calibration dependencies for all RSB. This article presents a deep convective cloud (DCC)-based calibration approach for an independent evaluation of the MODIS RSB response versus scan-angle (RVS) performance in C6.1. The long-term calibration stability and RVS differences in C6.1 have been significantly improved for Aqua-MODIS RSB. The observed RVS differences of more than 2% in Aqua-MODIS C6 bands 1 and 2 have been reduced to within 1% in C6.1. Some RSBs of Terra-MODIS have suffered temporal drifts up to 2% and calibration shifts up to 3%, particularly around 2016 when the Terra satellite entered into safe mode. The DCC approach has been found very effective in tracking the on-orbit RVS changes over time. calibration; clouds; Earth; radiometry; deep convective cloud; Moderate Resolution Imaging Spectroradiometer; MODIS; Moderate Resolution Imaging Spectroradiometer (MODIS); Terra satellite; remote sensing; VIIRS; Clouds and the Earth’s Radiant Energy System (CERES); Calibration; Cloud computing; Aqua satellites; Aqua-MODIS RSB; deep convective cloud (DCC); Earth Polychromatic Imaging Camera (EPIC); high-quality earth observation datasets; Mirrors; MODIS instruments; MODIS level 1B C6.1 dataset; MODIS reflective solar band calibration; onboard calibrators; radiometric calibration; response versus scan-angle (RVS); scan-angle calibration; Terra-MODIS
Bhatt, Rajendra; Doelling, David R.; Haney, Conor O.; Spangenberg, Douglas A.; Scarino, Benjamin R.; Gopalan, ArunBhatt, R., D. R. Doelling, C. O. Haney, D. A. Spangenberg, B. R. Scarino, A. Gopalan, 2020: Clouds and the Earth’s Radiant Energy System strategy for intercalibrating the new-generation geostationary visible imagers. Journal of Applied Remote Sensing, 14(3), 032410. doi: 10.1117/1.JRS.14.032410. The advanced baseline imager (ABI) instrument onboard Geostationary Operational Environmental Satellite (GOES)-16 is the first of National Oceanic and Atmospheric Administration (NOAA’s) new-generation geostationary earth orbiting (GEO) imagers that provides high-quality calibrated and geolocated Earth observations in six reflective solar bands (RSBs). The spectral similarity between the Visible Infrared Imaging Radiometer Suite (VIIRS) and ABI RSB offers an opportunity for deriving VIIRS-quality cloud retrievals from the ABI radiances. NASA’s Clouds and the Earth’s Radiant Energy System (CERES) project utilizes GEO imager (including ABI) radiances to retrieve clouds and derive broadband fluxes that are used to account for the regional diurnal flux variation between the CERES measurements and to convert the CERES observed radiances into fluxes. In order to derive a seamless cloud and flux datasets for CERES, it is important that the GEO, MODIS, and VIIRS imagers are all placed on the same radiometric scale. We describe an absolute radiometric intercomparison between the NOAA-20 VIIRS and GOES-16 ABI RSB using ray-matched radiance/reflectance pairs over all-sky tropical ocean scenes as well as a deep convective cloud invariant target calibration algorithm. Results indicate that the ABI and VIIRS RSB calibration are within 5%, except for the 0.47-μm band, for which the radiometric inconsistency is found to be ∼7 % . The GOES-16 radiometric scaling factors referenced to NOAA-20 VIIRS were computed from the two independent calibration methods to agree within 1% for ABI bands 1 to 4, and within 3% for bands 5 and 6. Results from this study were used to propose a future CERES GEO intercalibration algorithm referenced to NOAA-20 VIIRS, given the eventual demise of the Terra and Aqua satellites.
Loeb, Norman G.; Doelling, David R.Loeb, N. G., D. R. Doelling, 2020: CERES Energy Balanced and Filled (EBAF) from Afternoon-Only Satellite Orbits. Remote Sensing, 12(8), 1280. doi: 10.3390/rs12081280. The Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) data product uses a diurnal correction methodology to produce a shortwave (SW) top-of-atmosphere (TOA) radiative flux time series that accounts for diurnal cycle changes between CERES observation times while ensuring that the stability of the EBAF record is tied as closely as possible to CERES instrument calibration stability. The current EBAF Ed4.1 data product combines observations from Terra and Aqua after July 2002. However, the Terra satellite will start to drift in Mean Local Time (MLT) in early 2021, and Aqua’s MLT will start to drift in 2022. To ensure the EBAF record remains temporally stable, we explore the feasibility of using only CERES instruments from afternoon satellite orbits with a tight 1330 MLT after July 2002. We test this approach by directly comparing SW TOA fluxes generated after applying diurnal corrections to Aqua-only and to Terra + Aqua for 07/2002–06/2019. We find that global climatological mean SW TOA fluxes for these two cases are within 0.01 Wm−2 and the trend of the difference is < is 0.03 Wm−2 per decade. climate; radiation budget; diurnal
Loeb, Norman G.; Rose, Fred G.; Kato, Seiji; Rutan, David A.; Su, Wenying; Wang, Hailan; Doelling, David R.; Smith, William L.; Gettelman, AndrewLoeb, N. G., F. G. Rose, S. Kato, D. A. Rutan, W. Su, H. Wang, D. R. Doelling, W. L. Smith, A. Gettelman, 2020: Toward a Consistent Definition between Satellite and Model Clear-Sky Radiative Fluxes. J. Climate, 33(1), 61-75. doi: 10.1175/JCLI-D-19-0381.1. A new method of determining clear-sky radiative fluxes from satellite observations for climate model evaluation is presented. The method consists of applying adjustment factors to existing satellite clear-sky broadband radiative fluxes that make the observed and simulated clear-sky flux definitions more consistent. The adjustment factors are determined from the difference between observation-based radiative transfer model calculations of monthly mean clear-sky fluxes obtained by ignoring clouds in the atmospheric column and by weighting hourly mean clear-sky fluxes with imager-based clear-area fractions. The global mean longwave (LW) adjustment factor is −2.2 W m−2 at the top of the atmosphere and 2.7 W m−2 at the surface. The LW adjustment factors are pronounced at high latitudes during winter and in regions with high upper-tropospheric humidity and cirrus cloud cover, such as over the west tropical Pacific, and the South Pacific and intertropical convergence zones. In the shortwave (SW), global mean adjustment is 0.5 W m−2 at TOA and −1.9 W m−2 at the surface. It is most pronounced over sea ice off of Antarctica and over heavy aerosol regions, such as eastern China. However, interannual variations in the regional SW and LW adjustment factors are small compared to those in cloud radiative effect. After applying the LW adjustment factors, differences in zonal mean cloud radiative effect between observations and climate models decrease markedly between 60°S and 60°N and poleward of 65°N. The largest regional improvements occur over the west tropical Pacific and Indian Oceans. In contrast, the impact of the SW adjustment factors is much smaller.
Scarino, Benjamin R.; Bedka, Kristopher; Bhatt, Rajendra; Khlopenkov, Konstantin; Doelling, David R.; Smith Jr., William L.Scarino, B. R., K. Bedka, R. Bhatt, K. Khlopenkov, D. R. Doelling, W. L. Smith Jr., 2020: A kernel-driven BRDF model to inform satellite-derived visible anvil cloud detection. Atmospheric Measurement Techniques, 13(10), 5491-5511. doi: https://doi.org/10.5194/amt-13-5491-2020. Abstract. Satellites routinely observe deep convective clouds across the world. The cirrus outflow from deep convection, commonly referred to as anvil cloud, has a ubiquitous appearance in visible and infrared (IR) wavelength imagery. Anvil clouds appear as broad areas of highly reflective and cold pixels relative to the darker and warmer clear sky background, often with embedded textured and colder pixels that indicate updrafts and gravity waves. These characteristics would suggest that creating automated anvil cloud detection products useful for weather forecasting and research should be straightforward, yet in practice such product development can be challenging. Some anvil detection methods have used reflectance or temperature thresholding, but anvil reflectance varies significantly throughout a day as a function of combined solar illumination and satellite viewing geometry, and anvil cloud top temperature varies as a function of convective equilibrium level and tropopause height. This paper highlights a technique for facilitating anvil cloud detection based on visible observations that relies on comparative analysis with expected cloud reflectance for a given set of angles, thereby addressing limitations of previous methods. A 1-year database of anvil-identified pixels, as determined from IR observations, from several geostationary satellites was used to construct a bidirectional reflectance distribution function (BRDF) model to quantify typical anvil reflectance across almost all expected viewing, solar, and azimuth angle configurations, in addition to the reflectance uncertainty for each angular bin. Application of the BRDF model for cloud optical depth retrieval in deep convection is described as well.
Scarino, Benjamin; Doelling, David R.; Bhatt, Rajendra; Gopalan, Arun; Haney, ConorScarino, B., D. R. Doelling, R. Bhatt, A. Gopalan, C. Haney, 2020: Evaluating the Magnitude of VIIRS Out-of-Band Response for Varying Earth Spectra. Remote Sensing, 12(19), 3267. doi: 10.3390/rs12193267. Prior evaluations of Visible Infrared Imaging Radiometer Suite (VIIRS) out-of-band (OOB) contribution to total signal revealed specification exceedance for multiple key solar reflective and infrared bands that are of interest to the passive remote-sensing community. These assessments are based on laboratory measurements, and although highly useful, do not necessarily translate to OOB contribution with consideration of true Earth-reflected or Earth-emitted spectra, especially given the significant spectral variation of Earth targets. That is, although the OOB contribution of VIIRS is well known, it is not a uniform quantity applicable across all scene types. As such, this article quantifies OOB contribution for multiple relative spectral response characterization versions across the S-NPP, NOAA-20, and JPSS-2 VIIRS sensors as a function of varied SCIAMACHY- and IASI-measured hyperspectral Earth-reflected and Earth-emitted scenes. For instance, this paper reveals measured radiance variations of nearly 2% for the S-NPP VIIRS M5 (~0.67 μm) band, and up to 5.7% for certain VIIRS M9 (~1.38 μm) and M13 (~4.06 μm) bands that are owed solely to the truncation of OOB response for a set of spectrally distinct Earth scenes. If unmitigated, e.g., by only considering the published extended bandpass, such variations may directly translate to scene-dependent scaling discrepancies or subtle errors in vegetative index determinations. Therefore, knowledge of OOB effects is especially important for inter-calibration or environmental retrieval efforts that rely on specific or multiple categories of Earth scene spectra, and also to researchers whose products rely on the impacted channels. Additionally, instrument teams may find this evaluation method useful for pre-launch characterization of OOB contribution with specific Earth targets in mind rather than relying on general models. VIIRS; S-NPP; hyperspectral; in-band; JPSS-2; NOAA-20; out-of-band; spectral response
Scott, Ryan C.; Myers, Timothy A.; Norris, Joel R.; Zelinka, Mark D.; Klein, Stephen A.; Sun, Moguo; Doelling, David R.Scott, R. C., T. A. Myers, J. R. Norris, M. D. Zelinka, S. A. Klein, M. Sun, D. R. Doelling, 2020: Observed Sensitivity of Low-Cloud Radiative Effects to Meteorological Perturbations over the Global Oceans. J. Climate, 33(18), 7717-7734. doi: 10.1175/JCLI-D-19-1028.1.
Young, Cindy L.; Lukashin, Constantine; Taylor, Patrick C.; Swanson, Rand; Kirk, William S.; Cooney, Michael; Swartz, William H.; Goldberg, Arnold; Stone, Thomas; Jackson, Trevor; Doelling, David R.; Shaw, Joseph A.; Buleri, ChristineYoung, C. L., C. Lukashin, P. C. Taylor, R. Swanson, W. S. Kirk, M. Cooney, W. H. Swartz, A. Goldberg, T. Stone, T. Jackson, D. R. Doelling, J. A. Shaw, C. Buleri, 2020: Trutinor: A Conceptual Study for a Next-Generation Earth Radiant Energy Instrument. Remote Sensing, 12(20), 3281. doi: 10.3390/rs12203281. Uninterrupted and overlapping satellite instrument measurements of Earth’s radiation budget from space are required to sufficiently monitor the planet’s changing climate, detect trends in key climate variables, constrain climate models, and quantify climate feedbacks. The Clouds and Earth’s Radiant Energy System (CERES) instruments are currently making these vital measurements for the scientific community and society, but with modern technologies, there are more efficient and cost-effective alternatives to the CERES implementation. We present a compact radiometer concept, Trutinor (meaning “balance” in Latin), with two broadband channels, shortwave (0.2–3 μm) and longwave (5–50 μm), capable of continuing the CERES record by flying in formation with an existing imager on another satellite platform. The instrument uses a three-mirror off-axis anastigmat telescope as the front optics to image these broadband radiances onto a microbolometer array coated with gold black, providing the required performance across the full spectral range. Each pixel of the sensor has a field of view of 0.6°, which was chosen so the shortwave band can be efficiently calibrated using the Moon as an on-orbit light source with the same angular extent, thereby reducing mass and improving measurement accuracy, towards the goal of a gap-tolerant observing system. The longwave band will utilize compact blackbodies with phase-change cells for an absolute calibration reference, establishing a clear path for SI-traceability. Trutinor’s instrument breadboard has been designed and is currently being built and tested. earth radiation budget; CERES; climate change; carbon nanotubes; ARCSTONE; lunar calibration; microbolometer array; phase change cells; RAVAN; small satellite constellation
Angal, A.; Xiong, X.; Mu, Q.; Doelling, D. R.; Bhatt, R.; Wu, A.Angal, A., X. Xiong, Q. Mu, D. R. Doelling, R. Bhatt, A. Wu, 2018: Results From the Deep Convective Clouds-Based Response Versus Scan-Angle Characterization for the MODIS Reflective Solar Bands. IEEE Transactions on Geoscience and Remote Sensing, 56(2), 1115-1128. doi: 10.1109/TGRS.2017.2759660. The Terra and Aqua Moderate-Resolution Imaging Spectroradiometer (MODIS) scan mirror reflectance is a function of the angle of incidence (AOI) and was characterized prior to launch by the instrument vendor. The relative change of the prelaunch response versus scan angle (RVS) is tracked and linearly scaled on-orbit using observations at two AOIs of 11.2° and 50.2° corresponding to the moon view and solar diffuser, respectively. As the missions continue to operate well beyond their design life of six years, the assumption of linear scaling between the two AOIs is known to be inadequate in accurately characterizing the RVS, particularly at short wavelengths. Consequently, an enhanced approach of supplementing the on-board measurements with response trends from desert pseudoinvariant calibration sites (PICS) was formulated in MODIS Collection 6 (C6). An underlying assumption for the continued effectiveness of this approach is the long-term (multiyear) and short-term (month to month) stability of the PICS. Previous work has shown that the deep convective clouds (DCC) can also be used to monitor the on-orbit RVS performance with less trend uncertainties compared with desert sites. In this paper, the raw sensor response to the DCC is used to characterize the on-orbit RVS on a band and mirror-side basis. These DCC-based RVS results are compared with those of C6 PICS-based RVS, showing an agreement within 2% observed in most cases. The pros and cons of using a DCC-based RVS approach are also discussed in this paper. Although this reaffirms the efficacy of the C6 PICS-based RVS, the DCC-based RVS approach presents itself as an effective alternative for future considerations. Potential applications of this approach to other instruments, such as Suomi National Polar-orbiting Partnership, Joint Polar Satellite Systems, and Visible Infrared Imaging Radiometer Suite, are also discussed.
Bhatt, Rajendra; Doelling, David; Haney, Conor; Scarino, Benjamin; Gopalan, Arun; Bhatt, Rajendra; Doelling, David; Haney, Conor; Scarino, Benjamin; Gopalan, ArunBhatt, R., D. Doelling, C. Haney, B. Scarino, A. Gopalan, R. Bhatt, D. Doelling, C. Haney, B. Scarino, A. Gopalan, 2018: Consideration of Radiometric Quantization Error in Satellite Sensor Cross-Calibration. Remote Sensing, 10(7), 1131. doi: 10.3390/rs10071131. The radiometric resolution of a satellite sensor refers to the smallest increment in the spectral radiance that can be detected by the imaging sensor. The fewer bits that are used for signal discretization, the larger the quantization error in the measured radiance. In satellite inter-calibration, a difference in radiometric resolution between a reference and a target sensor can induce a calibration bias, if not properly accounted for. The effect is greater for satellites with a quadratic count response, such as the Geostationary Meteorological Satellite-5 (GMS-5) visible imager, where the quantization difference can introduce non-linearity in the inter-comparison datasets, thereby affecting the cross-calibration slope and offset. This paper describes a simulation approach to highlight the importance of considering the radiometric quantization in cross-calibration and presents a correction method for mitigating its impact. The method, when applied to the cross-calibration of GMS-5 and Terra Moderate Resolution Imaging Spectroradiometer (MODIS) sensors, improved the absolute calibration accuracy of the GMS-5 imager. This was validated via radiometric inter-comparison of GMS-5 and Multifunction Transport Satellite-2 (MTSAT-2) imager top-of-atmosphere (TOA) measurements over deep convective clouds (DCC) and Badain Desert invariant targets. The radiometric bias between GMS-5 and MTSAT-2 was reduced from 1.9% to 0.5% for DCC, and from 7.7% to 2.3% for Badain using the proposed correction method. calibration; MODIS; GMS-5; quantization
Doelling, David; Haney, Conor; Bhatt, Rajendra; Scarino, Benjamin; Gopalan, ArunDoelling, D., C. Haney, R. Bhatt, B. Scarino, A. Gopalan, 2018: Geostationary Visible Imager Calibration for the CERES SYN1deg Edition 4 Product. Remote Sensing, 10(2), 288. doi: 10.3390/rs10020288. The Clouds and the Earth’s Radiant Energy System (CERES) project relies on geostationary (GEO) imager derived TOA broadband fluxes and cloud properties to account for the regional diurnal fluctuations between the Terra and Aqua CERES and MODIS measurements. Anchoring the GEO visible calibration to the MODIS reference calibration and stability is critical for consistent fluxes and cloud retrievals across the 16 GEO imagers utilized in the CERES record. The CERES Edition 4A used GEO and MODIS ray-matched radiance pairs over all-sky tropical ocean (ATO-RM) to transfer the MODIS calibration to the GEO imagers. The primary GEO ATO-RM calibration was compared with the deep convective cloud (DCC) ray-matching and invariant desert/DCC target calibration methodologies, which are all tied to the same Aqua-MODIS calibration reference. Results indicate that most GEO record mean calibration method biases are within 1% with respect to ATO-RM. Most calibration method temporal trends were within 0.5% relative to ATO-RM. The monthly gain trend standard errors were mostly within 1% for all methods and GEOs. The close agreement amongst the independent calibration techniques validates all methodologies, and verifies that the coefficients are not artifacts of the methodology but rather adequately represent the true GEO visible imager degradation. calibration; MODIS; DCC; Earth invariant targets; geostationary; ray-matching
Haney, C.; Doelling, D.; Bhatt, R.; Scarino, B.; Gopalan, ArunHaney, C., D. Doelling, R. Bhatt, B. Scarino, A. Gopalan, 2018: Advances in utilizing deep convective cloud targets to inter-calibrate geostationary reflective solar band imagers with well calibrated imagers.
Kato, Seiji; Rose, Fred G.; Rutan, David A.; Thorsen, Tyler J.; Loeb, Norman G.; Doelling, David R.; Huang, Xianglei; Smith, William L.; Su, Wenying; Ham, Seung HeeKato, S., F. G. Rose, D. A. Rutan, T. J. Thorsen, N. G. Loeb, D. R. Doelling, X. Huang, W. L. Smith, W. Su, S. H. Ham, 2018: Surface Irradiances of Edition 4.0 Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) Data Product. J. Climate, 31(11), 4501–4527. doi: 10.1175/JCLI-D-17-0523.1. The algorithm to produce the Clouds and the Earth’s Energy System (CERES) Ed4.0 Energy Balanced and Filled (EBAF)-surface data product is explained. The algorithm forces computed top-of-atmosphere (TOA) irradiances to match with Ed4.0 EBAF-TOA irradiances by adjusting surface, cloud and atmospheric properties. Surface irradiances are subsequently adjusted using radiative kernels. The adjustment process is composed of two parts, bias correction and Lagrange multiplier. The bias in temperature and specific humidity between 200 hPa and 500 hPa used for the irradiance computation is corrected based on observations by Atmospheric Infrared Sounder (AIRS). Similarly, the bias in the cloud fraction is corrected based on observations by Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), and CloudSat. Remaining errors in surface, cloud and atmospheric properties are corrected in the Lagrange multiplier process. Ed4.0 global annual mean (January 2005 thorough December 2014) surface net shortwave (SW) and longwave (LW) irradiances, respectively, increases by 1.3 Wm-2 and decreases by 0.2 Wm-2 compared to EBAF Ed2.8 counterparts (the previous version), resulting increasing in net SW+LW surface irradiance by 1.1 Wm-2. The uncertainty in surface irradiances over ocean, land and polar regions at various spatial scales are estimated. The uncertainties in all-sky global annual mean upward and downward shortwave irradiance are, respectively, 3 Wm-2 and 4 Wm-2, and the uncertainties in upward and downward longwave irradiance are respectively, 3 Wm-2 and 6 Wm-2. With an assumption of all errors being independent the uncertainty in the global annual mean surface LW+SW net irradiance is 8 Wm-2.
Loeb, Norman G.; Doelling, David R.; Wang, Hailan; Su, Wenying; Nguyen, Cathy; Corbett, Joseph G.; Liang, Lusheng; Mitrescu, Cristian; Rose, Fred G.; Kato, SeijiLoeb, N. G., D. R. Doelling, H. Wang, W. Su, C. Nguyen, J. G. Corbett, L. Liang, C. Mitrescu, F. G. Rose, S. Kato, 2018: Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) Top-of-Atmosphere (TOA) Edition 4.0 Data Product. J. Climate, 31(2), 895–918. doi: 10.1175/JCLI-D-17-0208.1. The Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) top-of-atmosphere (TOA) Ed4.0 data product is described. EBAF Ed4.0 is an update to EBAF Ed2.8, incorporating all of the Ed4.0 suite of CERES data product algorithm improvements and consistent input datasets throughout the record. A one-time adjustment to SW and LW TOA fluxes is made to ensure that global mean net TOA flux for July 2005-June 2015 is consistent with the in-situ value of 0.71 W m–2. While global mean all-sky TOA flux differences between Ed4.0 and Ed2.8 are within 0.5 Wm-2, appreciable SW regional differences occur over marine stratocumulus and snow/sea-ice regions. Marked regional differences in SW clear-sky TOA flux occur in polar regions and dust areas over ocean. Clear-sky LW TOA fluxes in EBAF Ed4.0 exceed Ed2.8 in regions of persistent high cloud cover. Owing to substantial differences in global mean clear-sky TOA fluxes, the net cloud radiative effect in EBAF Ed4.0 is -18 Wm-2 compared to -21 Wm-2 in EBAF Ed2.8. We estimate the overall uncertainty in 1°x1° latitude-longitude regional monthly all-sky TOA flux to be 3 Wm-2 (1σ) for the Terra-only period and 2.5 Wm-2 for the Terra-Aqua period both for SW and LW. The SW clear-sky regional monthly uncertainty is estimated to be 6 Wm-2 for the Terra-only period and 5 Wm-2 for the Terra-Aqua period. The LW clear-sky regional monthly uncertainty is 5 Wm-2 for Terra-only and 4.5 Wm-2 for Terra-Aqua.
Su, Wenying; Liang, Lusheng; Doelling, David R.; Minnis, Patrick; Duda, David P.; Khlopenkov, Konstantin V.; Thieman, Mandana M.; Loeb, Norman G.; Kato, Seiji; Valero, Francisco P. J.; Wang, Hailan; Rose, Fred G.Su, W., L. Liang, D. R. Doelling, P. Minnis, D. P. Duda, K. V. Khlopenkov, M. M. Thieman, N. G. Loeb, S. Kato, F. P. J. Valero, H. Wang, F. G. Rose, 2018: Determining the Shortwave Radiative Flux from Earth Polychromatic Imaging Camera. Journal of Geophysical Research: Atmospheres, 123(20), 11,479-11,491. doi: 10.1029/2018JD029390. The Earth Polychromatic Imaging Camera (EPIC) onboard Deep Space Climate Observatory (DSCOVR) provides 10 narrowband spectral images of the sunlit side of the Earth. The blue (443 nm), green (551 nm), and red (680 nm) channels are used to derive EPIC broadband radiances based upon narrowband-to-broadband regressions developed using collocated MODIS equivalent channels and CERES broadband measurements. The pixel-level EPIC broadband radiances are averaged to provide global daytime means at all applicable EPIC times. They are converted to global daytime mean shortwave (SW) fluxes by accounting for the anisotropy characteristics using a cloud property composite based on lower Earth orbiting satellite imager retrievals and the CERES angular distribution models (ADMs). Global daytime mean SW fluxes show strong diurnal variations with daily maximum-minimum differences as great as 20 Wm−2 depending on the conditions of the sunlit portion of the Earth. The EPIC SW fluxes are compared against the CERES SYN1deg hourly SW fluxes. The global monthly mean differences (EPIC-SYN) between them range from 0.1 Wm−2 in July to -4.1 Wm−2 in January, and the RMS errors range from 3.2 Wm−2 to 5.2 Wm−2. Daily mean EPIC and SYN fluxes calculated using concurrent hours agree with each other to within 2% and both show a strong annual cycle. The SW flux agreement is within the calibration and algorithm uncertainties, which indicates that the method developed to calculate the global anisotropic factors from the CERES ADMs is robust and that the CERES ADMs accurately account for the Earth's anisotropy in the near-backscatter direction. CERES; angular distribution model; radiation; DSCOVR; EPIC; Lagrange-1 point
Sun-Mack, S.; Minnis, P.; Chen, Y.; Doelling, D. R.; Scarino, B. R.; Haney, C. O.; Smith, W. L.Sun-Mack, S., P. Minnis, Y. Chen, D. R. Doelling, B. R. Scarino, C. O. Haney, W. L. Smith, 2018: Calibration Changes to Terra MODIS Collection-5 Radiances for CERES Edition 4 Cloud Retrievals. IEEE Transactions on Geoscience and Remote Sensing, 1-17. doi: 10.1109/TGRS.2018.2829902. Previous research has revealed inconsistencies between the Collection 5 (C5) calibrations of certain channels common to the Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODISs). To achieve consistency between the Terra and Aqua MODIS radiances used in the Clouds and the Earth's Radiant Energy System (CERES) Edition 4 (Ed4) cloud property retrieval system, adjustments were developed and applied to the Terra C5 calibrations for channels 1-5, 7, 20, and 26. These calibration corrections, developed independently of those used for the later MODIS Collection 6 (C6), ranged from -3.0% for channel 5 to +4.3% for channel 26. For channel 20, the Terra C5 brightness temperatures were decreased nonlinearly by 0.55 K at 300-10 K or more at 220 K. The corrections were applied to the Terra C5 data for CERES Ed4 and resulted in Terra-Aqua radiance consistency that is as good as or better than that of the C6 data sets. The C5 adjustments led to more consistent Aqua and Terra cloud property retrievals than seen in the previous CERES edition. After Ed4 began processing, other calibration artifacts were found in some corrected channels and in some of the uncorrected thermal channels. Because no corrections were developed or applied for those artifacts, some anomalies or false trends could have been introduced into the Ed4 cloud property record. Thus, despite the much improved consistency achieved for the Terra and Aqua data sets in Ed4, the CERES Ed4 cloud property data sets should be used cautiously for cloud trend studies due to those remaining calibration artifacts. Earth; Satellites; cloud; Meteorology; climate; MODIS; Clouds and the Earth's Radiant Energy System (CERES); Moderate Resolution Imaging Spectroradiometer (MODIS); Market research; Clouds; Calibration
Bhatt, Rajendra; Doelling, David R.; Angal, Amit; Xiong, Xiaoxiong; Scarino, Benjamin; Gopalan, Arun; Haney, Conor; Wu, AishengBhatt, R., D. R. Doelling, A. Angal, X. Xiong, B. Scarino, A. Gopalan, C. Haney, A. Wu, 2017: Characterizing response versus scan-angle for MODIS reflective solar bands using deep convective clouds. Journal of Applied Remote Sensing, 11(1), 016014-016014. doi: 10.1117/1.JRS.11.016014. Abstract. MODIS consists of a cross-track, two-sided scan mirror, whose reflectance is not uniform but is a function of angle of incidence (AOI). This feature, known as response versus scan-angle (RVS), was characterized for all reflective solar bands of both MODIS instruments prior to launch. The RVS characteristic has changed on orbit, which must be tracked precisely over time to ensure the quality of MODIS products. The MODIS characterization support team utilizes the onboard calibrators and the earth view responses from multiple pseudoinvariant desert sites to track the RVS changes at different AOIs. The drawback of using deserts is the assumption that these sites are radiometrically stable during the monitoring period. In addition, the 16-day orbit repeat cycle of MODIS allows for only a limited set of AOIs over a given desert. We propose a novel and robust approach of characterizing the MODIS RVS using tropical deep convective clouds (DCC). The method tracks the monthly DCC response at specified sets of AOIs to compute the temporal RVS changes. Initial results have shown that the Aqua-MODIS collection 6 band 1 level 1B radiances show considerable residual RVS dependencies, with long-term drifts up to 2.3% at certain AOIs.
Bhatt, Rajendra; Doelling, David R.; Scarino, Benjamin; Haney, Conor; Gopalan, ArunBhatt, R., D. R. Doelling, B. Scarino, C. Haney, A. Gopalan, 2017: Development of Seasonal BRDF Models to Extend the Use of Deep Convective Clouds as Invariant Targets for Satellite SWIR-Band Calibration. Remote Sensing, 9(10), 1061. doi: 10.3390/rs9101061. Tropical deep convective clouds (DCC) are an excellent invariant target for vicarious calibration of satellite visible (VIS) and near-infrared (NIR) solar bands. The DCC technique (DCCT) is a statistical approach that collectively analyzes all identified DCC pixels on a monthly basis. The DCC reflectance in VIS and NIR spectrums is mainly a function of cloud optical depth, and provides a stable monthly statistical mode. However, for absorption shortwave infrared (SWIR) bands, the monthly DCC response is found to exhibit large seasonal cycles that make the implementation of the DCCT more challenging at these wavelengths. The seasonality assumption was tested using the SNPP-VIIRS SWIR bands, with up to 50% of the monthly DCC response temporal variation removed through deseasonalization. In this article, a monthly DCC bidirectional reflectance distribution function (BRDF) approach is proposed, which is found to be comparable to or can outperform the effects of deseasonalization alone. To demonstrate that the SNPP-VIIRS DCC BRDF can be applied to other JPSS VIIRS imagers in the same 13:30 sun-synchronous orbit, the VIIRS DCC BRDF was applied to Aqua-MODIS. The Aqua-MODIS SWIR band DCC reflectance natural variability is reduced by up to 45% after applying the VIIRS-based monthly DCC BRDFs. calibration; MODIS; VIIRS; BRDF; DCC; JPSS; SWIR bands
Eitzen, Zachary A.; Su, Wenying; Xu, Kuan-Man; Loeb, Norman; Sun, Moguo; Doelling, David; Rose, Fred; Bodas-Salcedo, AlejandroEitzen, Z. A., W. Su, K. Xu, N. Loeb, M. Sun, D. Doelling, F. Rose, A. Bodas-Salcedo, 2017: Evaluation of a general circulation model by the CERES Flux-by-cloud type simulator. Journal of Geophysical Research: Atmospheres, 122(20), 10,655–10,668. doi: 10.1002/2017JD027076. In this work, we use the CERES FluxByCloudTyp data product (FBCTObs), which calculates TOA shortwave and longwave fluxes for cloud types defined by cloud optical depth (τ) and cloud top pressure (pc), and the CERES Flux-by-cloud type simulator (FBCTSim) to evaluate the HadGEM2-A model. FBCTSim is comprised of a cloud generator that produces subcolumns with profiles of binary cloud fraction, a cloud property simulator that determines the cloud type (τ, pc) for each subcolumn, and a radiative transfer model that calculates TOA fluxes. The identification of duplicate subcolumns greatly reduces the number of radiative transfer calculations required. In the Southern Great Plains region in January, February, and December (JFD) 2008, FBCTSim shows that HadGEM2-A cloud tops are higher in altitude than in FBCTObs, but also have higher values of OLR than in FBCTObs, leading to a compensating error that results in an average value of OLR that is close to observed. When FBCTSim is applied to the Southeast Pacific stratocumulus region in JJA 2008, the cloud tops are primarily low in altitude; however, the clouds tend to be less numerous, and have higher optical depths than are observed. In addition, the HadGEM2-A albedo is higher than that of FBCTObs for those cloud types that occur most frequently. FBCTSim is also applied to the entire 60° N to 60° S region, and it is found that there are both fewer clouds and higher albedos than observed for most cloud types, which represents a compensating error in terms of the shortwave radiative budget. CERES; 0321 Cloud/radiation interaction; 3337 Global climate models; 3394 Instruments and techniques; 3360 Remote sensing; model evaluation; Instrument simulator
Doelling, David R.; Haney, Conor O.; Scarino, Benjamin R.; Gopalan, Arun; Bhatt, RajendraDoelling, D. R., C. O. Haney, B. R. Scarino, A. Gopalan, R. Bhatt, 2016: Improvements to the geostationary visible imager ray-matching calibration algorithm for CERES Edition 4. J. Atmos. Oceanic Technol., 33(12), 2679–2698. doi: 10.1175/JTECH-D-16-0113.1. The Clouds and the Earth’s Radiant Energy System CERES project relies on geostationary- (GEO) imager-derived TOA broadband fluxes and cloud properties to account for the regional diurnal fluctuations between the Terra and Aqua CERES and MODIS measurements. The CERES project employs a ray-matching calibration algorithm in order to transfer the Aqua-MODIS calibration to the GEO imagers, thereby allowing the derivation of consistent fluxes and cloud retrievals across the 16 GEO imagers utilized in the CERES record. The CERES Edition 4 processing scheme grants the opportunity to recalibrate the GEO record using an improved GEO/MODIS all-sky ocean ray-matching algorithm. Using a graduated angle matching method, which is most restrictive for anisotropic clear-sky ocean radiances and least restrictive for isotropic bright cloud radiances, reduces the bidirectional bias while preserving the dynamic range. Furthermore, SCIAMACHY hyperspectral radiances are used to account for both the solar incoming and Earth reflected spectra in order to correct spectral band differences. As a result, the difference between the linear regression offset and the maintained GEO space count was reduced, and the calibration slopes computed from the linear fit and the regression through the space count agreed to within 0.4%. A deep convective cloud (DCC) ray-matching algorithm is also presented. The all-sky ocean and DCC ray-matching timeline gains are within 0.7% of one another. Because DCC are isotropic and the brightest Earth targets with near uniform visible spectra, the temporal standard error of GEO imager gains are reduced by up to 60% from that of all-sky ocean targets.
Doelling, David R.; Sun, Moguo; Nguyen, Le Trang; Nordeen, Michele L.; Haney, Conor O.; Keyes, Dennis F.; Mlynczak, Pamela E.Doelling, D. R., M. Sun, L. T. Nguyen, M. L. Nordeen, C. O. Haney, D. F. Keyes, P. E. Mlynczak, 2016: Advances in Geostationary-Derived Longwave Fluxes for the CERES Synoptic (SYN1deg) Product. J. Atmos. Oceanic Technol., 33(3), 503-521. doi: 10.1175/JTECH-D-15-0147.1. The Clouds and the Earth’s Radiant Energy System (CERES) project has provided the climate community 15 years of globally observed top-of-the-atmosphere fluxes critical for climate and cloud feedback studies. To accurately monitor the earth’s radiation budget, the CERES instrument footprint fluxes must be spatially and temporally averaged properly. The CERES synoptic 1° (SYN1deg) product incorporates derived fluxes from the geostationary satellites (GEOs) to account for the regional diurnal flux variations in between Terra and Aqua CERES measurements. The Edition 4 CERES reprocessing effort has provided the opportunity to reevaluate the derivation of longwave (LW) fluxes from GEO narrowband radiances by examining the improvements from incorporating 1-hourly versus 3-hourly GEO data, additional GEO infrared (IR) channels, and multichannel GEO cloud properties. The resultant GEO LW fluxes need to be consistent across the 16-satellite climate data record. To that end, the addition of the water vapor channel, available on all GEOs, was more effective than using a reanalysis dataset’s column-weighted relative humidity combined with the window channel radiance. The benefit of the CERES LW angular directional model to derive fluxes was limited by the inconsistency of the GEO cloud retrievals. Greater success was found in the direct conversion of window and water vapor channel radiances into fluxes. Incorporating 1-hourly GEO fluxes had the greatest impact on improving the accuracy of high-temporal-resolution fluxes, and normalizing the GEO LW fluxes with CERES greatly reduced the monthly regional LW flux bias.
Khlopenkov, Konstantin V.; Doelling, David R.Khlopenkov, K. V., D. R. Doelling, 2016: Development of image processing method to detect noise in geostationary imagery. SPIE 10004, Image and Signal Processing for Remote Sensing XXII, 10004, 100041S-100041S-9. doi: 10.1117/12.2241544. The Clouds and the Earth’s Radiant Energy System (CERES) has incorporated imagery from 16 individual geostationary (GEO) satellites across five contiguous domains since March 2000. In order to derive broadband fluxes uniform across satellite platforms it is important to ensure a good quality of the input raw count data. GEO data obtained by older GOES imagers (such as MTSAT-1, Meteosat-5, Meteosat-7, GMS-5, and GOES-9) are known to frequently contain various types of noise caused by transmission errors, sync errors, stray light contamination, and others. This work presents an image processing methodology designed to detect most kinds of noise and corrupt data in all bands of raw imagery from modern and historic GEO satellites. The algorithm is based on a set of different approaches to detect abnormal image patterns, including inter-line and inter-pixel differences within a scanline, correlation between scanlines, analysis of spatial variance, and also a 2D Fourier analysis of the image spatial frequencies. In spite of computational complexity, the described method is highly optimized for performance to facilitate volume processing of multi-year data and runs in fully automated mode. Reliability of this noise detection technique has been assessed by human supervision for each GEO dataset obtained during selected time periods in 2005 and 2006. This assessment has demonstrated the overall detection accuracy of over 99.5% and the false alarm rate of under 0.3%. The described noise detection routine is currently used in volume processing of historical GEO imagery for subsequent production of global gridded data products and for cross-platform calibration.
Loeb, N. G.; Su, W.; Doelling, D. R.; Wong, T.; Minnis, P.; Thomas, S.; Miller, W. F.Loeb, N. G., W. Su, D. R. Doelling, T. Wong, P. Minnis, S. Thomas, W. F. Miller, 2016: Earth's Top-of-Atmosphere Radiation Budget. Reference Module in Earth Systems and Environmental Sciences. The top-of-atmosphere (TOA) Earth radiation budget (ERB) is a key property of the climate system that describes the balance between how much solar energy the Earth absorbs and how much terrestrial thermal infrared radiation it emits. This article provides an overview of the instruments and algorithms used to observe the TOA ERB by the Clouds and the Earth's Radiant Energy System (CERES) project. We summarize the properties of the CERES instruments, their calibration, combined use of CERES and imager measurements for improved cloud-radiation properties, and the approaches used for time interpolation and space averaging of TOA radiative fluxes. calibration; clouds; longwave; shortwave; broadband; CERES; climate; radiation budget; top-of-atmosphere; flux; Time interpolation
Doelling, D.R.; Wu, A.; Xiong, X.; Scarino, B.R.; Bhatt, R.; Haney, C.O.; Morstad, D.; Gopalan, A.Doelling, D., A. Wu, X. Xiong, B. Scarino, R. Bhatt, C. Haney, D. Morstad, A. Gopalan, 2015: The Radiometric Stability and Scaling of Collection 6 Terra- and Aqua-MODIS VIS, NIR, and SWIR Spectral Bands. IEEE Transactions on Geoscience and Remote Sensing, 53(8), 4520-4535. doi: 10.1109/TGRS.2015.2400928. The Moderate Resolution Imaging Spectroradiometer (MODIS) Calibration Team has recently released the Collection 6 (C6) radiances, which offer broad improvements over Collection 5 (C5). The recharacterization of the solar diffuser, lunar measurements, and scan mirror angle corrections removed most of the visible channel calibration drifts. The visible band calibration stability was validated over the Libyan Desert, Dome-C, and deep convective cloud (DCC) invariant Earth targets, for wavelengths less than 1 . The lifetime stability of Terra and Aqua C6 is both within 1%, whereas the Terra C5 degradation exceeded 2% for most visible bands. The MODIS lifetime radiance trends over the invariant targets are mostly within 1%; however, the band-specific target fluctuations are inconsistent, which suggests that the stability limits of the invariant targets have been reached. Based on Terra- and Aqua-MODIS nearly simultaneous nadir overpass (NSNO) radiance comparisons, the Terra and Aqua C6 calibration shows agreement within 1.2%, whereas the C5 calibration exceeds 2%. Because the MODIS instruments are alike, the same NSNOs are used to radiometrically scale the Terra radiances to Aqua. For most visible bands, the Terra-scaled and Aqua C6 radiances are consistent to within 0.5% over Dome-C, DCC, and for geostationary visible imagers having similar spectral response functions, which are used as transfer radiometers. For bands greater than 1 , only minor calibration adjustments were made, and the C6 calibration is stable within 1% based on Libya-4. calibration; Earth; MODIS; Moderate Resolution Imaging Spectroradiometer (MODIS); intercalibration; Degradation; Market research; pseudoinvariant calibration sites (PICS); radiometric scaling; Standards
Doelling, David R.; Khlopenkov, Konstantin V.; Okuyama, Arata; Haney, Conor O.; Gopalan, Arun; Scarino, Benjamin R.; Nordeen, Michele; Bhatt, Rajandra; Avey, LanceDoelling, D. R., K. V. Khlopenkov, A. Okuyama, C. O. Haney, A. Gopalan, B. R. Scarino, M. Nordeen, R. Bhatt, L. Avey, 2015: MTSAT-1R Visible Imager Point Spread Correction Function, Part I: The Need for, Validation of, and Calibration With. IEEE Transactions on Geoscience and Remote Sensing, 53(3), 1513-1526. doi: 10.1109/TGRS.2014.2344678.
Khlopenkov, Konstantin V.; Doelling, David R.; Okuyama, ArataKhlopenkov, K. V., D. R. Doelling, A. Okuyama, 2015: MTSAT-1R Visible Imager Point Spread Function Correction, Part II: Theory. IEEE Transactions on Geoscience and Remote Sensing, 53(3), 1504-1512. doi: 10.1109/TGRS.2014.2344627.
Rutan, David A.; Kato, Seiji; Doelling, David R.; Rose, Fred G.; Nguyen, Le Trang; Caldwell, Thomas E.; Loeb, Norman G.Rutan, D. A., S. Kato, D. R. Doelling, F. G. Rose, L. T. Nguyen, T. E. Caldwell, N. G. Loeb, 2015: CERES Synoptic Product: Methodology and Validation of Surface Radiant Flux. J. Atmos. Oceanic Technol., 32(6), 1121-1143. doi: 10.1175/JTECH-D-14-00165.1. AbstractThe Clouds and the Earth’s Radiant Energy System Synoptic (SYN1deg), edition 3, product provides climate-quality global 3-hourly 1° × 1°gridded top of atmosphere, in-atmosphere, and surface radiant fluxes. The in-atmosphere surface fluxes are computed hourly using a radiative transfer code based upon inputs from Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS), 3-hourly geostationary (GEO) data, and meteorological assimilation data from the Goddard Earth Observing System. The GEO visible and infrared imager calibration is tied to MODIS to ensure uniform MODIS-like cloud properties across all satellite cloud datasets. Computed surface radiant fluxes are compared to surface observations at 85 globally distributed land (37) and ocean buoy (48) sites as well as several other publicly available global surface radiant flux data products. Computed monthly mean downward fluxes from SYN1deg have a bias (standard deviation) of 3.0 W m−2 (5.7%) for shortwave and −4.0 W m−2 (2.9%) for longwave compared to surface observations. The standard deviation between surface downward shortwave flux calculations and observations at the 3-hourly time scale is reduced when the diurnal cycle of cloud changes is explicitly accounted for. The improvement is smaller for surface downward longwave flux owing to an additional sensitivity to boundary layer temperature/humidity, which has a weaker diurnal cycle compared to clouds. radiative transfer; satellite observations; Climate records; Surface fluxes
Stanfield, Ryan E.; Dong, Xiquan; Xi, Baike; Del Genio, Anthony D.; Minnis, Patrick; Doelling, David; Loeb, NormanStanfield, R. E., X. Dong, B. Xi, A. D. Del Genio, P. Minnis, D. Doelling, N. Loeb, 2015: Assessment of NASA GISS CMIP5 and Post-CMIP5 Simulated Clouds and TOA Radiation Budgets Using Satellite Observations. Part II: TOA Radiation Budget and CREs. J. Climate, 28(5), 1842-1864. doi: 10.1175/JCLI-D-14-00249.1. AbstractIn Part I of this study, the NASA GISS Coupled Model Intercomparison Project (CMIP5) and post-CMIP5 (herein called C5 and P5, respectively) simulated cloud properties were assessed utilizing multiple satellite observations, with a particular focus on the southern midlatitudes (SMLs). This study applies the knowledge gained from Part I of this series to evaluate the modeled TOA radiation budgets and cloud radiative effects (CREs) globally using CERES EBAF (CE) satellite observations and the impact of regional cloud properties and water vapor on the TOA radiation budgets. Comparisons revealed that the P5- and C5-simulated global means of clear-sky and all-sky outgoing longwave radiation (OLR) match well with CE observations, while biases are observed regionally. Negative biases are found in both P5- and C5-simulated clear-sky OLR. P5-simulated all-sky albedo slightly increased over the SMLs due to the increase in low-level cloud fraction from the new planetary boundary layer (PBL) scheme. Shortwave, longwave, and net CRE are quantitatively analyzed as well. Regions of strong large-scale atmospheric upwelling/downwelling motion are also defined to compare regional differences across multiple cloud and radiative variables. In general, the P5 and C5 simulations agree with the observations better over the downwelling regime than over the upwelling regime. Comparing the results herein with the cloud property comparisons presented in Part I, the modeled TOA radiation budgets and CREs agree well with the CE observations. These results, combined with results in Part I, have quantitatively estimated how much improvement is found in the P5-simulated cloud and radiative properties, particularly over the SMLs and tropics, due to the implementation of the new PBL and convection schemes. Radiation budgets; Model evaluation/performance; climate models; Cloud parameterizations; Cloud radiative effects; Model comparison
Bhatt, Rajendra; Doelling, David R.; Wu, Aisheng; Xiong, Xiaoxiong (Jack); Scarino, Benjamin R.; Haney, Conor O.; Gopalan, ArunBhatt, R., D. R. Doelling, A. Wu, X. Xiong, B. R. Scarino, C. O. Haney, A. Gopalan, 2014: Initial Stability Assessment of S-NPP VIIRS Reflective Solar Band Calibration Using Invariant Desert and Deep Convective Cloud Targets. Remote Sensing, 6(4), 2809-2826. doi: 10.3390/rs6042809. The latest CERES FM-5 instrument launched onboard the S-NPP spacecraft will use the VIIRS visible radiances from the NASA Land Product Evaluation and Analysis Tool Elements (PEATE) product for retrieving the cloud properties associated with its TOA flux measurement. In order for CERES to provide climate quality TOA flux datasets, the retrieved cloud properties must be consistent throughout the record, which is dependent on the calibration stability of the VIIRS imager. This paper assesses the NASA calibration stability of the VIIRS reflective solar bands using the Libya-4 desert and deep convective clouds (DCC). The invariant targets are first evaluated for temporal natural variability. It is found for visible (VIS) bands that DCC targets have half of the variability of Libya-4. For the shortwave infrared (SWIR) bands, the desert has less variability. The brief VIIRS record and target variability inhibits high confidence in identifying any trends that are less than ±0.6%/yr for most VIS bands, and ±2.5%/yr for SWIR bands. None of the observed invariant target reflective solar band trends exceeded these trend thresholds. Initial assessment results show that the VIIRS data have been consistently calibrated and that the VIIRS instrument stability is similar to or better than the MODIS instrument. CERES; MODIS; invariant calibration targets; radiometric stability; S-NPP VIIRS; satellite calibration
Khlopenkov, Konstantin V.; Doelling, David R.; Okuyama, ArataKhlopenkov, K. V., D. R. Doelling, A. Okuyama, 2014: Development of 2D deconvolution method to repair blurred MTSAT-1R visible imagery. doi: 10.1117/12.2061121. Spatial cross-talk has been discovered in the visible channel data of the Multi-functional Transport Satellite (MTSAT)-1R. The slight image blurring is attributed to an imperfection in the mirror surface caused either by flawed polishing or a dust contaminant. An image processing methodology is described that employs a two-dimensional deconvolution routine to recover the original undistorted MTSAT-1R data counts. The methodology assumes that the dispersed portion of the signal is small and distributed randomly around the optical axis, which allows the image blurring to be described by a point spread function (PSF) based on the Gaussian profile. The PSF is described by 4 parameters, which are solved using a maximum likelihood estimator using coincident collocated MTSAT-2 images as truth. A subpixel image matching technique is used to align the MTSAT-2 pixels into the MTSAT-1R projection and to correct for navigation errors and cloud displacement due to the time and viewing geometry differences between the two satellite observations. An optimal set of the PSF parameters is derived by an iterative routine based on the 4-dimensional Powell’s conjugate direction method that minimizes the difference between PSF-corrected MTSAT-1R and collocated MTSAT-2 images. This iterative approach is computationally intensive and was optimized analytically as well as by coding in assembly language incorporating parallel processing. The PSF parameters were found to be consistent over the 5-days of available daytime coincident MTSAT-1R and MTSAT-2 images, and can easily be applied to the MTSAT-1R imager pixel level counts to restore the original quality of the entire MTSAT-1R record.
Smith, G. Louis; Doelling, David R.Smith, G. L., D. R. Doelling, 2014: Computation of Radiation Budget on an Oblate Earth. J. Climate, 27(19), 7203-7206. doi: 10.1175/JCLI-D-14-00058.1. AbstractThe effects of the earth’s oblateness on computation of its radiation budget from satellite measurements are evaluated. For the Clouds and the Earth’s Radiant Energy System (CERES) data processing, geolocations of the measurements are computed in terms of the geodetic coordinate system. Using this system accounts for oblateness in the computed solar zenith angle and length of day. The geodetic and geocentric latitudes are equal at the equator and poles but differ by a maximum of 0.2° at 45° latitude. The area of each region and zone is affected by oblateness as compared to geocentric coordinates, decreasing from zero at the equator to 1.5% at the poles. The global area receiving solar radiation is calculated using the equatorial and polar axes. This area varies with solar declination by 0.0005. For radiation budget computations, the earth oblateness effects are shown to be small compared to error sources of measuring or modeling. Coordinate systems
Doelling, David R.; Loeb, Norman G.; Keyes, Dennis F.; Nordeen, Michele L.; Morstad, Daniel; Nguyen, Cathy; Wielicki, Bruce A.; Young, David F.; Sun, MoguoDoelling, D. R., N. G. Loeb, D. F. Keyes, M. L. Nordeen, D. Morstad, C. Nguyen, B. A. Wielicki, D. F. Young, M. Sun, 2013: Geostationary Enhanced Temporal Interpolation for CERES Flux Products. J. Atmos. Oceanic Technol., 30(6), 1072-1090. doi: 10.1175/JTECH-D-12-00136.1.
Kato, Seiji; Loeb, Norman G.; Rose, Fred G.; Doelling, David R.; Rutan, David A.; Caldwell, Thomas E.; Yu, Lisan; Weller, Robert A.Kato, S., N. G. Loeb, F. G. Rose, D. R. Doelling, D. A. Rutan, T. E. Caldwell, L. Yu, R. A. Weller, 2013: Surface Irradiances Consistent with CERES-Derived Top-of-Atmosphere Shortwave and Longwave Irradiances. J. Climate, 26(9), 2719-2740. doi: 10.1175/JCLI-D-12-00436.1. AbstractThe estimate of surface irradiance on a global scale is possible through radiative transfer calculations using satellite-retrieved surface, cloud, and aerosol properties as input. Computed top-of-atmosphere (TOA) irradiances, however, do not necessarily agree with observation-based values, for example, from the Clouds and the Earth’s Radiant Energy System (CERES). This paper presents a method to determine surface irradiances using observational constraints of TOA irradiance from CERES. A Lagrange multiplier procedure is used to objectively adjust inputs based on their uncertainties such that the computed TOA irradiance is consistent with CERES-derived irradiance to within the uncertainty. These input adjustments are then used to determine surface irradiance adjustments. Observations by the Atmospheric Infrared Sounder (AIRS), Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), CloudSat, and Moderate Resolution Imaging Spectroradiometer (MODIS) that are a part of the NASA A-Train constellation provide the uncertainty estimates. A comparison with surface observations from a number of sites shows that the bias [root-mean-square (RMS) difference] between computed and observed monthly mean irradiances calculated with 10 years of data is 4.7 (13.3) W m−2 for downward shortwave and −2.5 (7.1) W m−2 for downward longwave irradiances over ocean and −1.7 (7.8) W m−2 for downward shortwave and −1.0 (7.6) W m−2 for downward longwave irradiances over land. The bias and RMS error for the downward longwave and shortwave irradiances over ocean are decreased from those without constraint. Similarly, the bias and RMS error for downward longwave over land improves, although the constraint does not improve downward shortwave over land. This study demonstrates how synergetic use of multiple instruments (CERES, MODIS, CALIPSO, CloudSat, AIRS, and geostationary satellites) improves the accuracy of surface irradiance computations. Radiative fluxes; Energy budget/balance; Radiation budgets; radiative transfer
Wielicki, Bruce A.; Young, D. F.; Mlynczak, M. G.; Thome, K. J.; Leroy, S.; Corliss, J.; Anderson, J. G.; Ao, C.O.; Bantges, R.; Best, F.; Bowman, K.; Brindley, H.; Butler, J. J.; Collins, W.; Dykema, J. A.; Doelling, D. R.; Feldman, D. R.; Fox, N.; Huang, X.; Holz, R.; Huang, Y.; Jin, Z.; Jennings, D.; Johnson, D. G.; Jucks, K.; Kato, S.; Kirk-Davidoff, D. B.; Knuteson, R.; Kopp, G.; Kratz, D. P.; Liu, X.; Lukashin, C.; Mannucci, A. J.; Phojanamongkolkij, N.; Pilewskie, P.; Ramaswamy, V.; Revercomb, H.; Rice, J.; Roberts, Y.; Roithmayr, C. M.; Rose, F.; Sandford, S.; Shirley, E. L.; Smith, W.L.; Soden, B.; Speth, P. W.; Sun, W.; Taylor, P.C.; Tobin, D.; Xiong, X.Wielicki, B. A., D. F. Young, M. G. Mlynczak, K. J. Thome, S. Leroy, J. Corliss, J. G. Anderson, C. Ao, R. Bantges, F. Best, K. Bowman, H. Brindley, J. J. Butler, W. Collins, J. A. Dykema, D. R. Doelling, D. R. Feldman, N. Fox, X. Huang, R. Holz, Y. Huang, Z. Jin, D. Jennings, D. G. Johnson, K. Jucks, S. Kato, D. B. Kirk-Davidoff, R. Knuteson, G. Kopp, D. P. Kratz, X. Liu, C. Lukashin, A. J. Mannucci, N. Phojanamongkolkij, P. Pilewskie, V. Ramaswamy, H. Revercomb, J. Rice, Y. Roberts, C. M. Roithmayr, F. Rose, S. Sandford, E. L. Shirley, W. Smith, B. Soden, P. W. Speth, W. Sun, P. Taylor, D. Tobin, X. Xiong, 2013: Achieving Climate Change Absolute Accuracy in Orbit. Bull. Amer. Meteor. Soc., 130308154356007. doi: 10.1175/BAMS-D-12-00149.1.
Hong, Gang; Minnis, Patrick; Doelling, David; Ayers, J. Kirk; Sun-Mack, SzedungHong, G., P. Minnis, D. Doelling, J. K. Ayers, S. Sun-Mack, 2012: Estimating effective particle size of tropical deep convective clouds with a look-up table method using satellite measurements of brightness temperature differences. Journal of Geophysical Research: Atmospheres, 117(D6), D06207. doi: 10.1029/2011JD016652. A method for estimating effective ice particle radius Re at the tops of tropical deep convective clouds (DCC) is developed on the basis of precomputed look-up tables (LUTs) of brightness temperature differences (BTDs) between the 3.7 and 11.0 μm bands. A combination of discrete ordinates radiative transfer and correlated k distribution programs, which account for the multiple scattering and monochromatic molecular absorption in the atmosphere, is utilized to compute the LUTs as functions of solar zenith angle, satellite zenith angle, relative azimuth angle, Re, cloud top temperature (CTT), and cloud visible optical thickness τ. The LUT-estimated DCC Re agrees well with the cloud retrievals of the Moderate Resolution Imaging Spectroradiometer (MODIS) for the NASA Clouds and Earth's Radiant Energy System with a correlation coefficient of 0.988 and differences of less than 10%. The LUTs are applied to 1 year of measurements taken from MODIS aboard Aqua in 2007 to estimate DCC Re and are compared to a similar quantity from CloudSat over the region bounded by 140°E, 180°E, 0°N, and 20°N in the Western Pacific Warm Pool. The estimated DCC Re values are mainly concentrated in the range of 25–45 μm and decrease with CTT. Matching the LUT-estimated Re with ice cloud Re retrieved by CloudSat, it is found that the ice cloud τ values from DCC top to the vertical location where LUT-estimated Re is located at the CloudSat-retrieved Re profile are mostly less than 2.5 with a mean value of about 1.3. Changes in the DCC τ can result in differences of less than 10% for Re estimated from LUTs. The LUTs of 0.65 μm bidirectional reflectance distribution function (BRDF) are built as functions of viewing geometry and column amount of ozone above upper troposphere. The 0.65 μm BRDF can eliminate some noncore portions of the DCCs detected using only 11 μm brightness temperature thresholds, which result in a mean difference of only 0.6 μm for DCC Re estimated from BTD LUTs. 0320 Cloud physics and chemistry; 3371 Tropical convection; brightness temperature difference; deep convection; effective particle size; look-up table
Loeb, Norman G.; Kato, Seiji; Su, Wenying; Wong, Takmeng; Rose, Fred G.; Doelling, David R.; Norris, Joel R.; Huang, XiangleiLoeb, N. G., S. Kato, W. Su, T. Wong, F. G. Rose, D. R. Doelling, J. R. Norris, X. Huang, 2012: Advances in Understanding Top-of-Atmosphere Radiation Variability from Satellite Observations. Surveys in Geophysics, 33(3-4), 359-385. doi: 10.1007/s10712-012-9175-1. This paper highlights how the emerging record of satellite observations from the Earth Observation System (EOS) and A-Train constellation are advancing our ability to more completely document and understand the underlying processes associated with variations in the Earth’s top-of-atmosphere (TOA) radiation budget. Large-scale TOA radiation changes during the past decade are observed to be within 0.5 Wm−2 per decade based upon comparisons between Clouds and the Earth’s Radiant Energy System (CERES) instruments aboard Terra and Aqua and other instruments. Tropical variations in emitted outgoing longwave (LW) radiation are found to closely track changes in the El Niño-Southern Oscillation (ENSO). During positive ENSO phase (El Niño), outgoing LW radiation increases, and decreases during the negative ENSO phase (La Niña). The coldest year during the last decade occurred in 2008, during which strong La Nina conditions persisted throughout most of the year. Atmospheric Infrared Sounder (AIRS) observations show that the lower temperatures extended throughout much of the troposphere for several months, resulting in a reduction in outgoing LW radiation and an increase in net incoming radiation. At the global scale, outgoing LW flux anomalies are partially compensated for by decreases in midlatitude cloud fraction and cloud height, as observed by Moderate Resolution Imaging Spectrometer and Multi-angle Imaging SpectroRadiometer, respectively. CERES data show that clouds have a net radiative warming influence during La Niña conditions and a net cooling influence during El Niño, but the magnitude of the anomalies varies greatly from one ENSO event to another. Regional cloud-radiation variations among several Terra and A-Train instruments show consistent patterns and exhibit marked fluctuations at monthly timescales in response to tropical atmosphere-ocean dynamical processes associated with ENSO and Madden–Julian Oscillation. clouds; radiation budget; Geophysics/Geodesy; Astronomy, Observations and Techniques; Earth Sciences, general; Climate variability
Loeb, Norman G.; Lyman, John M.; Johnson, Gregory C.; Allan, Richard P.; Doelling, David R.; Wong, Takmeng; Soden, Brian J.; Stephens, Graeme L.Loeb, N. G., J. M. Lyman, G. C. Johnson, R. P. Allan, D. R. Doelling, T. Wong, B. J. Soden, G. L. Stephens, 2012: Observed changes in top-of-the-atmosphere radiation and upper-ocean heating consistent within uncertainty. Nature Geoscience, 5(2), 110-113. doi: 10.1038/ngeo1375. Global climate change results from a small yet persistent imbalance between the amount of sunlight absorbed by Earth and the thermal radiation emitted back to space. An apparent inconsistency has been diagnosed between interannual variations in the net radiation imbalance inferred from satellite measurements and upper-ocean heating rate from in situ measurements, and this inconsistency has been interpreted as ‘missing energy’ in the system. Here we present a revised analysis of net radiation at the top of the atmosphere from satellite data, and we estimate ocean heat content, based on three independent sources. We find that the difference between the heat balance at the top of the atmosphere and upper-ocean heat content change is not statistically significant when accounting for observational uncertainties in ocean measurements, given transitions in instrumentation and sampling. Furthermore, variability in Earth’s energy imbalance relating to El Niño-Southern Oscillation is found to be consistent within observational uncertainties among the satellite measurements, a reanalysis model simulation and one of the ocean heat content records. We combine satellite data with ocean measurements to depths of 1,800 m, and show that between January 2001 and December 2010, Earth has been steadily accumulating energy at a rate of 0.50±0.43 Wm−2 (uncertainties at the 90% confidence level). We conclude that energy storage is continuing to increase in the sub-surface ocean. Oceanography; Atmospheric science; Climate science
Goldberg, M.; Ohring, G.; Butler, J.; Cao, C.; Datla, R.; Doelling, D.; Gärtner, V.; Hewison, T.; Iacovazzi, B.; Kim, D.; Kurino, T.; Lafeuille, J.; Minnis, P.; Renaut, D.; Schmetz, J.; Tobin, D.; Wang, L.; Weng, F.; Wu, X.; Yu, F.; Zhang, P.; Zhu, T.Goldberg, M., G. Ohring, J. Butler, C. Cao, R. Datla, D. Doelling, V. Gärtner, T. Hewison, B. Iacovazzi, D. Kim, T. Kurino, J. Lafeuille, P. Minnis, D. Renaut, J. Schmetz, D. Tobin, L. Wang, F. Weng, X. Wu, F. Yu, P. Zhang, T. Zhu, 2011: The Global Space-Based Inter-Calibration System. Bull. Amer. Meteor. Soc., 92(4), 467-475. doi: 10.1175/2010BAMS2967.1. The Global Space-based Inter-Calibration System (GSICS) is a new international program to assure the comparability of satellite measurements taken at different times and locations by different instruments operated by different satellite agencies. Sponsored by the World Meteorological Organization and the Coordination Group for Meteorological Satellites, GSICS will intercalibrate the instruments of the international constellation of operational low-earth-orbiting (LEO) and geostationary earth-orbiting (GEO) environmental satellites and tie these to common reference standards. The intercomparability of the observations will result in more accurate measurements for assimilation in numerical weather prediction models, construction of more reliable climate data records, and progress toward achieving the societal goals of the Global Earth Observation System of Systems. GSICS includes globally coordinated activities for prelaunch instrument characterization, onboard routine calibration, sensor intercomparison of near-simultaneous observations of individual scenes or overlapping time series, vicarious calibration using Earth-based or celestial references, and field campaigns. An initial strategy uses high-accuracy satellite instruments, such as the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) and Atmospheric Infrared Sounder (AIRS) and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT)'s Centre National d'Études Spatiales (CNES) Infrared Atmospheric Sounding Interferometer (IASI), as space-based reference standards for intercalibrating the operational satellite sensors. Examples of initial intercalibration results and future plans are presented. Agencies participating in the program include the Centre National d'Études Spatiales, China Meteorological Administration, EUMETSAT, Japan Meteorological Agency, Korea Meteorological Administration, NASA, National Institute of Standards and Technology, and NOAA.
Mlynczak, Pamela E.; Smith, G. Louis; Doelling, David R.Mlynczak, P. E., G. L. Smith, D. R. Doelling, 2011: The Annual Cycle of Earth Radiation Budget from Clouds and the Earth’s Radiant Energy System (CERES) Data. J. Appl. Meteor. Climatol., 50(12), 2490-2503. doi: 10.1175/JAMC-D-11-050.1. AbstractThe seasonal cycle of the Earth radiation budget is investigated by use of data from the Clouds and the Earth’s Radiant Energy System (CERES). Monthly mean maps of reflected solar flux and Earth-emitted flux on a 1° equal-angle grid are used for the study. The seasonal cycles of absorbed solar radiation (ASR), outgoing longwave radiation (OLR), and net radiation are described by use of principal components for the time variations, for which the corresponding geographic variations are the empirical orthogonal functions. Earth’s surface is partitioned into land and ocean for the analysis. The first principal component describes more than 95% of the variance in the seasonal cycle of ASR and the net radiation fluxes and nearly 90% of the variance of OLR over land. Because one term can express so much of the variance, principal component analysis is very useful to describe these seasonal cycles. The annual cycles of ASR are about 100 W m−2 over land and ocean, but the amplitudes of OLR are about 27 W m−2 over land and 15 W m−2 over ocean. The magnitude of OLR and its time lag relative to that of ASR are important descriptors of the climate system and are computed for the first principal components. OLR lags ASR by about 26 days over land and 42 days over ocean. The principal components are useful for comparing the observed radiation budget with that computed by a model. Energy budget/balance
Smith, G. L.; Priestley, K. J.; Loeb, N. G.; Wielicki, B. A.; Charlock, T. P.; Minnis, P.; Doelling, D. R.; Rutan, D. A.Smith, G. L., K. J. Priestley, N. G. Loeb, B. A. Wielicki, T. P. Charlock, P. Minnis, D. R. Doelling, D. A. Rutan, 2011: Clouds and Earth Radiant Energy System (CERES), a review: Past, present and future. Advances in Space Research, 48(2), 254-263. doi: 10.1016/j.asr.2011.03.009. The Clouds and Earth Radiant Energy System (CERES) project’s objectives are to measure the reflected solar radiance (shortwave) and Earth-emitted (longwave) radiances and from these measurements to compute the shortwave and longwave radiation fluxes at the top of the atmosphere (TOA) and the surface and radiation divergence within the atmosphere. The fluxes at TOA are to be retrieved to an accuracy of 2%. Improved bidirectional reflectance distribution functions (BRDFs) have been developed to compute the fluxes at TOA from the measured radiances with errors reduced from ERBE by a factor of two or more. Instruments aboard the Terra and Aqua spacecraft provide sampling at four local times. In order to further reduce temporal sampling errors, data are used from the geostationary meteorological satellites to account for changes of scenes between observations by the CERES radiometers. A validation protocol including in-flight calibrations and comparisons of measurements has reduced the instrument errors to less than 1%. The data are processed through three editions. The first edition provides a timely flow of data to investigators and the third edition provides data products as accurate as possible with resources available. A suite of cloud properties retrieved from the MODerate-resolution Imaging Spectroradiometer (MODIS) by the CERES team is used to identify the cloud properties for each pixel in order to select the BRDF for each pixel so as to compute radiation fluxes from radiances. Also, the cloud information is used to compute radiation at the surface and through the atmosphere and to facilitate study of the relationship between clouds and the radiation budget. The data products from CERES include, in addition to the reflected solar radiation and Earth emitted radiation fluxes at TOA, the upward and downward shortwave and longwave radiation fluxes at the surface and at various levels in the atmosphere. Also at the surface the photosynthetically active radiation and ultraviolet radiation (total, UVA and UVB) are computed. The CERES instruments aboard the Terra and Aqua spacecraft have served well past their design life times. A CERES instrument has been integrated onto the NPP platform and is ready for launch in 2011. Another CERES instrument is being built for launch in 2014, and plans are being made for a series of follow-on missions. earth radiation budget; radiometry
Stackhouse Jr, PW; Wong, T.; Loeb, N. G; Kratz, D. P.; Wilber, A. C.; Doelling, D. R.; Nguyen, L. CathyStackhouse Jr, P., T. Wong, N. G. Loeb, D. P. Kratz, A. C. Wilber, D. R. Doelling, L. C. Nguyen, 2010: Earth Radiation Budget at top-of-atmosphere [in "State of the Climate in 2009”]. Bull. Amer. Meteor. Soc., 91(7), S41. doi: 10.1175/BAMS-91-7-StateoftheClimate.
Loeb, Norman G.; Wielicki, Bruce A.; Doelling, David R.; Smith, G. Louis; Keyes, Dennis F.; Kato, Seiji; Manalo-Smith, Natividad; Wong, TakmengLoeb, N. G., B. A. Wielicki, D. R. Doelling, G. L. Smith, D. F. Keyes, S. Kato, N. Manalo-Smith, T. Wong, 2009: Toward Optimal Closure of the Earth's Top-of-Atmosphere Radiation Budget. J. Climate, 22(3), 748-766. doi: 10.1175/2008JCLI2637.1. Abstract Despite recent improvements in satellite instrument calibration and the algorithms used to determine reflected solar (SW) and emitted thermal (LW) top-of-atmosphere (TOA) radiative fluxes, a sizeable imbalance persists in the average global net radiation at the TOA from satellite observations. This imbalance is problematic in applications that use earth radiation budget (ERB) data for climate model evaluation, estimate the earth’s annual global mean energy budget, and in studies that infer meridional heat transports. This study provides a detailed error analysis of TOA fluxes based on the latest generation of Clouds and the Earth’s Radiant Energy System (CERES) gridded monthly mean data products [the monthly TOA/surface averages geostationary (SRBAVG-GEO)] and uses an objective constrainment algorithm to adjust SW and LW TOA fluxes within their range of uncertainty to remove the inconsistency between average global net TOA flux and heat storage in the earth–atmosphere system. The 5-yr global mean CERES net flux from the standard CERES product is 6.5 W m−2, much larger than the best estimate of 0.85 W m−2 based on observed ocean heat content data and model simulations. The major sources of uncertainty in the CERES estimate are from instrument calibration (4.2 W m−2) and the assumed value for total solar irradiance (1 W m−2). After adjustment, the global mean CERES SW TOA flux is 99.5 W m−2, corresponding to an albedo of 0.293, and the global mean LW TOA flux is 239.6 W m−2. These values differ markedly from previously published adjusted global means based on the ERB Experiment in which the global mean SW TOA flux is 107 W m−2 and the LW TOA flux is 234 W m−2. Radiation budgets; satellite observations; Fluxes
Minnis, P.; Trepte, Q. Z.; Sun-Mack, S.; Chen, Y.; Doelling, D. R.; Young, D. F.; Spangenberg, D. A.; Miller, W. F.; Wielicki, B. A.; Brown, R. R.; Gibson, S. C.; Geier, E. B.Minnis, P., Q. Z. Trepte, S. Sun-Mack, Y. Chen, D. R. Doelling, D. F. Young, D. A. Spangenberg, W. F. Miller, B. A. Wielicki, R. R. Brown, S. C. Gibson, E. B. Geier, 2008: Cloud Detection in Nonpolar Regions for CERES Using TRMM VIRS and Terra and Aqua MODIS Data. Ieee Transactions on Geoscience and Remote Sensing, 46(11), 3857-3884. doi: 10.1109/tgrs.2008.2001351. Objective techniques have been developed to consistently identify cloudy pixels over nonpolar regions in multispectral imager data coincident with measurements taken by the Clouds and Earth's Radiant Energy System (CERES) on the Tropical Rainfall Measuring Mission (TRMM), Terra, and Aqua satellites. The daytime method uses the 0.65-, 3.8-, 10.8-, and 12.0-mu m channels on the TRMM Visible and Infrared Scanner (VIRS) and the Terra and Aqua MODIS. The VIRS and Terra 1.6-mu m channel and the Aqua 1.38- and 2.1-mu m channels are used secondarily. The primary nighttime radiances are from the 3.8-, 10.8-, and 12.0-mu m channels. Significant differences were found between the VIRS and Terra 1.6-mu m and the Terra and Aqua 3.8-mu m channels' calibrations. Cascading threshold tests provide clear or cloudy classifications that are qualified according to confidence levels or other conditions, such as sunglint, that affect the classification. The initial infrared threshold test classifies similar to 43% of the pixels as clouds. The next level seeks consistency in three (two) different channels during daytime (nighttime) and accounts for roughly 40% (25%) of the pixels. The third tier uses refined thresholds to classify remaining pixels. For cloudy pixels, similar to 4% yield no retrieval when analyzed with a cloud retrieval algorithm. The techniques were applied to data between 1998 and 2006 to yield average nonpolar cloud amounts of similar to 0.60. Averages among the platforms differ by < 0.01 and are comparable to surface climatological values, but roughly 0.07 less than means from two other satellite analyses, primarily as a result of missing small subpixel and thin clouds.
Minnis, Patrick; Doelling, David R.; Nguyen, Louis; Miller, Walter F.; Chakrapani, VenkatesanMinnis, P., D. R. Doelling, L. Nguyen, W. F. Miller, V. Chakrapani, 2008: Assessment of the Visible Channel Calibrations of the VIRS on TRMM and MODIS on Aqua and Terra. J. Atmos. Oceanic Technol., 25(3), 385-400. doi: 10.1175/2007JTECHA1021.1. Abstract Several recent research satellites carry self-calibrating multispectral imagers that can be used for calibrating operational imagers lacking complete self-calibrating capabilities. In particular, the visible (VIS, 0.65 μm) channels on operational meteorological satellites are generally calibrated before launch, but require vicarious calibration techniques to monitor the gains and offsets once they are in orbit. To ensure that the self-calibrating instruments are performing as expected, this paper examines the consistencies between the VIS channel (channel 1) reflectances of the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua satellites and the version 5a and 6 reflectances of the Visible Infrared Scanner (VIRS) on the Tropical Rainfall Measuring Mission using a variety of techniques. These include comparisons of Terra and Aqua VIS radiances with coincident broadband shortwave radiances from the well-calibrated Clouds and the Earth’s Radiant Energy System (CERES), time series of deep convective cloud (DCC) albedos, and ray-matching intercalibrations between each of the three satellites. Time series of matched Terra and VIRS data, Aqua and VIRS data, and DCC reflected fluxes reveal that an older version (version 5a, ending in early 2004) of the VIRS calibration produced a highly stable record, while the latest version (version 6) appears to overestimate the sensor gain change by ∼1% yr−1 as the result of a manually induced gain adjustment. Comparisons with the CERES shortwave radiances unearthed a sudden change in the Terra MODIS calibration that caused a 1.17% decrease in the gain on 19 November 2003 that can be easily reversed. After correction for these manual adjustments, the trends in the VIRS and Terra channels are no greater than 0.1% yr−1. Although the results were more ambiguous, no statistically significant trends were found in the Aqua MODIS channel 1 gain. The Aqua radiances are 1% greater, on average, than their Terra counterparts, and after normalization are 4.6% greater than VIRS radiances, in agreement with theoretical calculations. The discrepancy between the two MODIS instruments should be taken into account to ensure consistency between parameters derived from them. With the adjustments, any of the three instruments can serve as references for calibrating other satellites. Monitoring of the calibrations continues in near–real time and the results are available via the World Wide Web. rainfall; satellite observations; Instrumentation/sensors; Sensitivity studies
Loeb, N. G.; Kato, S.; Loukachine, K.; Manalo-Smith, N.; Doelling, D. R.Loeb, N. G., S. Kato, K. Loukachine, N. Manalo-Smith, D. R. Doelling, 2007: Angular distribution models for top-of-atmosphere radiative flux estimation from the Clouds and the Earth's Radiant Energy System instrument on the Terra satellite. Part II: Validation. J. Atmos. Oceanic Technol., 24(4), 564-584. doi: 10.1175/jtech1983.1. Errors in top- of- atmosphere ( TOA) radiative fluxes from the Clouds and the Earth's Radiant Energy System ( CERES) instrument due to uncertainties in radiance- to- flux conversion from CERES Terra angular distribution models ( ADMs) are evaluated through a series of consistency tests. These tests show that the overall bias in regional monthly mean shortwave ( SW) TOA flux is less than 0.2Wm(-2) and the regional RMS error ranges from 0.70 to 1.4 W m(-2). In contrast, SW TOA fluxes inferred using theoretical ADMs that assume clouds are plane parallel are overestimated by 3 - 4 W m(-2) and exhibit a strong latitudinal dependence. In the longwave ( LW), the bias error ranges from 0.2 to 0.4 W m(-2) and regional RMS errors remain smaller than 0.7 W m(-2). Global mean albedos derived from ADMs developed during the Earth Radiation Budget Experiment ( ERBE) and applied to CERES measurements show a systematic increase with viewing zenith angle of 4% - 8%, while albedos from the CERES Terra ADMs show a smaller increase of 1% - 2%. The LW fluxes from the ERBE ADMs show a systematic decrease with viewing zenith angle of 2% - 2.4%, whereas fluxes from the CERES Terra ADMs remain within 0.7% - 0.8% at all angles. Based on several months of multiangle CERES along- track data, the SW TOA flux consistency between nadir-and oblique- viewing zenith angles is generally 5% ( < 17 W m(-2)) over land and ocean and 9% ( 26 W m(-2)) in polar regions, and LW TOA flux consistency is approximate 3% ( 7 W m(-2)) over all surfaces. Based on these results and a theoretically derived conversion between TOA flux consistency and TOA flux error, the best estimate of the error in CERES TOA flux due to the radiance- to- flux conversion is 3% ( 10 W m(-2)) in the SW and 1.8% ( 3 - 5 W m(-2)) in the LW. Monthly mean TOA fluxes based on ERBE ADMs are larger than monthly mean TOA fluxes based on CERES Terra ADMs by 1.8 and 1.3 W m(-2) in the SW and LW, respectively.
Loeb, Norman G.; Wielicki, Bruce A.; Rose, Fred G.; Doelling, David R.Loeb, N. G., B. A. Wielicki, F. G. Rose, D. R. Doelling, 2007: Variability in global top-of-atmosphere shortwave radiation between 2000 and 2005. Geophysical Research Letters, 34(3), L03704. doi: 10.1029/2006GL028196. Measurements from various instruments and analysis techniques are used to directly compare changes in Earth-atmosphere shortwave (SW) top-of-atmosphere (TOA) radiation between 2000 and 2005. Included in the comparison are estimates of TOA reflectance variability from published ground-based Earthshine observations and from new satellite-based CERES, MODIS and ISCCP results. The ground-based Earthshine data show an order-of-magnitude more variability in annual mean SW TOA flux than either CERES or ISCCP, while ISCCP and CERES SW TOA flux variability is consistent to 40%. Most of the variability in CERES TOA flux is shown to be dominated by variations global cloud fraction, as observed using coincident CERES and MODIS data. Idealized Earthshine simulations of TOA SW radiation variability for a lunar-based observer show far less variability than the ground-based Earthshine observations, but are still a factor of 4–5 times more variable than global CERES SW TOA flux results. Furthermore, while CERES global albedos exhibit a well-defined seasonal cycle each year, the seasonal cycle in the lunar Earthshine reflectance simulations is highly variable and out-of-phase from one year to the next. Radiative transfer model (RTM) approaches that use imager cloud and aerosol retrievals reproduce most of the change in SW TOA radiation observed in broadband CERES data. However, assumptions used to represent the spectral properties of the atmosphere, clouds, aerosols and surface in the RTM calculations can introduce significant uncertainties in annual mean changes in regional and global SW TOA flux. 1610 Atmosphere; 1640 Remote sensing; radiative flux; albedo; 1616 Climate variability; Variability
Mace, Gerald G.; Benson, Sally; Sonntag, Karen L.; Kato, Seiji; Min, Qilong; Minnis, Patrick; Twohy, Cynthia H.; Poellot, Michael; Dong, Xiquan; Long, Charles; Zhang, Qiuqing; Doelling, David R.Mace, G. G., S. Benson, K. L. Sonntag, S. Kato, Q. Min, P. Minnis, C. H. Twohy, M. Poellot, X. Dong, C. Long, Q. Zhang, D. R. Doelling, 2006: Cloud radiative forcing at the Atmospheric Radiation Measurement Program Climate Research Facility: 1. Technique, validation, and comparison to satellite-derived diagnostic quantities. Journal of Geophysical Research: Atmospheres, 111(D11), D11S90. doi: 10.1029/2005JD005921. It has been hypothesized that continuous ground-based remote sensing measurements from collocated active and passive remote sensors combined with regular soundings of the atmospheric thermodynamic structure can be combined to describe the effects of clouds on the clear sky radiation fluxes. We critically test that hypothesis in this paper and a companion paper (part 2). Using data collected at the Southern Great Plains (SGP) Atmospheric Radiation Measurement (ARM) site sponsored by the U.S. Department of Energy, we explore an analysis methodology that results in the characterization of the physical state of the atmospheric profile at time resolutions of 5 min and vertical resolutions of 90 m. The description includes thermodynamics and water vapor profile information derived by merging radiosonde soundings with ground-based data and continues through specification of the cloud layer occurrence and microphysical and radiative properties derived from retrieval algorithms and parameterizations. The description of the atmospheric physical state includes a calculation of the clear and cloudy sky solar and infrared flux profiles. Validation of the methodology is provided by comparing the calculated fluxes with top of atmosphere (TOA) and surface flux measurements and by comparing the total column optical depths to independently derived estimates. We find over a 1-year period of comparison in overcast uniform skies that the calculations are strongly correlated to measurements with biases in the flux quantities at the surface and TOA of less than 6% and median fractional errors ranging from 12% to as low as 2%. In the optical depth comparison for uniform overcast skies during the year 2000 where the optical depth varies over more than 3 orders of magnitude we find a mean positive bias of less than 1% and a 0.6 correlation coefficient. In addition to a case study where we examine the cloud radiative effects at the TOA, surface and atmosphere by a middle latitude cyclone, we examine the cloud top pressure and optical depth retrievals of ISCCP and LBTM over a period of 1 year. Using overcast periods from the year 2000, we find that the satellite algorithms tend to compare well with data overall but there is a tendency to bias cloud tops into the middle troposphere and underestimate optical depth in high optical depth events. clouds; Remote sensing; 3311 Clouds and aerosols; 3359 Radiative processes; 3310 Clouds and cloud feedbacks; 3394 Instruments and techniques; radiation
Minnis, Patrick; Gambheer, Arvind V.; Doelling, David R.Minnis, P., A. V. Gambheer, D. R. Doelling, 2004: Azimuthal anisotropy of longwave and infrared window radiances from the Clouds and the Earth's Radiant Energy System on the Tropical Rainfall Measuring Mission and Terra satellites. Journal of Geophysical Research: Atmospheres, 109(D8). doi: https://doi.org/10.1029/2003JD004471. Shadowing by vegetation, landforms, or clouds can reduce the surface temperature relative to unshadowed portions of the same land area. This shading effect can cause azimuthal variation of the outgoing infrared radiance that is currently not taken into account in remote sensing and Earth radiation budget analyses. In this paper, multiangle longwave (LW) (5–200 μm) and window (WN) (8–12 μm) radiances taken by the Clouds and the Earth's Radiant Energy System (CERES) rotating azimuth plane scanner on the Tropical Rainfall Measuring Mission (TRMM) and Terra satellites are used to determine the azimuthal anisotropy of LW and WN fields over all solar zenith angles and surface types in clear and cloudy conditions. The azimuthal component of the anisotropy is isolated by constructing limb-darkening models for each category of surface type and topography in each solar zenith angle (SZA) bin. The viewing zenith angle dependence of WN and LW radiances in clear scenes depends on the SZA, possibly because of changes in the boundary layer temperature structure during the day. The observed mean radiances, in general, are greater when viewing the sunlit hemisphere (backscattering) than when viewing the shaded (forward scattering) hemisphere. This forward-back contrast increases with increasing terrain roughness and is stronger for surfaces with open vegetation such as shrubs and grass than for contiguous vegetation like forests. The anisotropy is less well defined for barren deserts. Maximum anisotropy occurs for SZAs between 48° and 70°. This paper provides the first evidence that clouds also induce longwave azimuthal anisotropy. Strong forward-back radiance contrast is evident for partly, mostly, and overcast scenes for SZA < 48°. The contrast disappears for overcast scenes and decreases for partly and mostly cloudy scenes at higher SZAs. The TRMM sampling is limited and causes some biases at particular angle sets but overall provides a reasonable depiction of the anisotropy at all SZAs. Terra yields a more accurate anisotropy characterization but only for SZAs between 48° and 70°. A simple model constructed from the TRMM results for clear scenes reduces clear-sky temperature prediction RMS errors by 38% or more while minimizing the biases associated with azimuthal anisotropy. The model should yield similar or better reductions in the errors associated with retrievals of skin temperature or LW fluxes, especially those from geostationary satellites. In addition, future analyses of combined TRMM, Terra, and Aqua CERES data will likely provide more accurate correction models that could further reduce errors in surface skin temperature and radiative flux for both clear and cloudy scenes. surface temperature; infrared radiation; remote sensing
Minnis, Patrick; Nguyen, Louis; Doelling, David R.; Young, David F.; Miller, Walter F.; Kratz, David P.Minnis, P., L. Nguyen, D. R. Doelling, D. F. Young, W. F. Miller, D. P. Kratz, 2002: Rapid Calibration of Operational and Research Meteorological Satellite Imagers. Part I: Evaluation of Research Satellite Visible Channels as References. J. Atmos. Oceanic Technol., 19(9), 1233-1249. doi: 10.1175/1520-0426(2002)019<1233:RCOOAR>2.0.CO;2. Abstract Operational meteorological satellites generally lack reliable onboard calibration systems for solar-imaging channels. Current methods for calibrating these channels and for normalizing similar channels on contemporaneous satellite imagers typically rely on a poorly calibrated reference source. To establish a more reliable reference instrument for calibration normalization, this paper examines the use of research satellite imagers that maintain their solar-channel calibrations by using onboard diffuser systems that rely on the sun as an absolute reference. The Visible Infrared Scanner (VIRS) on the Tropical Rainfall Measuring Mission (TRMM) satellite and the second Along-Track Scanning Radiometer (ATSR-2) on the second European Remote Sensing Satellite (ERS-2) are correlated with matched data from the eighth Geostationary Operational Environmental Satellite (GOES-8), the fifth Geostationary Meteorological satellite (GMS-5), and with each other to examine trends in the solar channels. VIRS data are also correlated with the Terra satellite's Moderate Resolution Imaging Spectroradiometer (MODIS) provisional data as a preliminary assessment of their relative calibrations. As an additional check on their long-term stability, the VIRS data are compared to the relevant corresponding broadband shortwave radiances of the Clouds and the Earth's Radiant Energy System (CERES) scanners on TRMM. No statistically significant trend in the calibration of the VIRS 0.65- and 1.64-μm channels could be detected from the comparisons with CERES data taken during 1998 and 2000. The VIRS-to-GOES-8 correlations revealed an annual degradation rate for the GOES-8 visible (0.67 μm) channel of ∼7.5% and an initial drop of 16% in the gain from the prelaunch value. The slopes in the GOES-8 visible-channel gain trend lines derived from VIRS data taken after January 1998 and ATSR-2 data taken between October 1995 and December 1999 differed by only 1%–2% indicating that both reference instruments are highly stable. The mean difference of 3%–4.8% between the VIRS–GOES-8 and ATSR-2–GOES-8 gains is attributed to spectral differences between ATSR-2 and VIRS and to possible biases in the ATSR-2 channel-2 calibration. A degradation rate of 1.3% per year found for the GMS-5 visible channel was confirmed by comparisons with earlier calibrations. The MODIS and VIRS calibrations agreed to within −1% to 3%. Some of the differences between VIRS and the provisional MODIS radiances can be explained by spectral differences between the two instruments. The MODIS measures greater reflectance than VIRS for bright scenes. Although both VIRS and ATSR-2 provide temporally stable calibrations, it is recommended that, at least until MODIS calibrations are finalized, VIRS should be used as a reference source for normalizing operational meteorological satellite imagers because of its broader visible filter.
Minnis, Patrick; Nguyen, Louis; Doelling, David R.; Young, David F.; Miller, Walter F.; Kratz, David P.Minnis, P., L. Nguyen, D. R. Doelling, D. F. Young, W. F. Miller, D. P. Kratz, 2002: Rapid Calibration of Operational and Research Meteorological Satellite Imagers. Part II: Comparison of Infrared Channels. J. Atmos. Oceanic Technol., 19(9), 1250-1266. doi: 10.1175/1520-0426(2002)019<1250:RCOOAR>2.0.CO;2. Abstract To establish a more reliable reference instrument for calibration normalization, this paper examines the differences between the various thermal infrared imager channels on a set of research and operational satellites. Mean brightness temperatures from the Visible Infrared Scanner (VIRS) on the Tropical Rainfall Measuring Mission (TRMM) satellite and the second Along-Track Scanning Radiometer (ATSR-2) on the second European Remote Sensing Satellite (ERS-2) are correlated with matched data from the eighth Geostationary Operational Environmental Satellite (GOES-8), the fifth Geostationary Meteorological Satellite (GMS-5), and with each other. VIRS data are also correlated with the Terra satellite's Moderate Resolution Imaging Spectroradiometer (MODIS) provisional data as a preliminary assessment of their relative calibrations. As an additional check on their long-term stability, the VIRS data are compared to the broadband longwave radiances of the Clouds and the Earth's Radiant Energy System (CERES) scanners on TRMM. No statistically significant trend in the calibration of any of the three (3.7, 10.8, and 12.0 μm) VIRS thermal channels could be detected from the comparisons with CERES data taken during 1998 and 2000 indicating that the VIRS channels can serve as a reliable reference for intercalibrating satellite imagers. However, a small day–night difference in the VIRS thermal channels detected at very low temperatures should be taken into account. In general, most of the channels agreed to within less than ±0.7 K over a temperature range between 200 and 300 K. Some of the smaller differences can be explained by spectral differences in the channel response functions. A few larger differences were found at 200 K for some of the channels suggesting some basic calibration differences for lower temperatures. A nearly 3-K bias in the ATSR-2 11-μm channel relative to VIRS and GOES-8 was found at the cold end of the temperature range. The intercalibrations described here are being continued on a routine basis.
Doelling, David R.; Minnis, Patrick; Spangenberg, Douglas A.; Chakrapani, Venkatesan; Mahesh, Ashwin; Pope, Shelly K.; Valero, Francisco P. J.Doelling, D. R., P. Minnis, D. A. Spangenberg, V. Chakrapani, A. Mahesh, S. K. Pope, F. P. J. Valero, 2001: Cloud radiative forcing at the top of the atmosphere during FIRE ACE derived from AVHRR data. Journal of Geophysical Research: Atmospheres, 106(D14), 15279-15296. doi: 10.1029/2000JD900455. Cloud radiative forcing at the top of the atmosphere is derived from narrowband visible and infrared radiances from NOAA-12 and NOAA-14 advanced very high resolution radiometer (AVHRR) data taken over the Arctic Ocean during the First ISCCP Regional Experiment Arctic Cloud Experiment (FIRE ACE) during spring and summer 1998. Shortwave and longwave fluxes at the top of the atmosphere (TOA) were computed using narrowband-to-broadband conversion formulae based on coincident Earth Radiation Budget Experiment (ERBE) broadband and AVHRR narrowband radiances. The NOAA-12/NOAA-14 broadband data were validated using model calculations and coincident broadband flux radiometer data from the Surface Heat Budget of the Arctic Ocean experiment and from aircraft data. The AVHRR TOA albedos agreed with the surface- and aircraft-based albedos to within one standard deviation of ±0.029 on an instantaneous basis. Mean differences ranged from −0.012 to 0.023 depending on the radiometer and platform. AVHRR-derived longwave fluxes differed from the model calculations using aircraft- and surface-based fluxes by −0.2 to −0.3 W m−2, on average, when the atmospheric profiles were adjusted to force agreement between the observed and the calculated downwelling fluxes. The standard deviations of the differences were less than 2%. Mean total TOA albedo for the domain between 72°N and 80°N and between 150°W and 180°W changed from 0.695 in May to 0.510 during July, while the longwave flux increased from 217 to 228 W m−2. Net radiation increased from −89 to −2 W m−2 for the same period. Net cloud forcing varied from −15 W m−2 in May to −31 W m−2 during July, while longwave cloud forcing was nearly constant at ∼8 W m−2. Shortwave cloud forcing dominated the cloud effect, ranging from −22 W m−2 during May to −40 W m−2 in July. The mean albedos and fluxes are consistent with previous measurements from the ERBE, except during May when the albedo and longwave flux were greater than the maximum ERBE values. The cloud-forcing results, while similar to some earlier estimates, are the most accurate values hitherto obtained for regions in the Arctic. When no significant melting was present, the clear-sky longwave flux showed a diurnal variation similar to that over land under clear skies. These data should be valuable for understanding the Arctic energy budget and for constraining models of atmosphere and ocean processes in the Arctic. 3359 Meteorology and Atmospheric Dynamics: Radiative processes; 3309 Meteorology and Atmospheric Dynamics: Climatology; 3349 Meteorology and Atmospheric Dynamics: Polar meteorology; 9315 Information Related to Geographic Region: Arctic region
Minnis, Patrick; Chakrapani, Venkatesan; Doelling, David R.; Nguyen, Louis; Palikonda, Rabindra; Spangenberg, Douglas A.; Uttal, Taneil; Arduini, Robert F.; Shupe, MatthewMinnis, P., V. Chakrapani, D. R. Doelling, L. Nguyen, R. Palikonda, D. A. Spangenberg, T. Uttal, R. F. Arduini, M. Shupe, 2001: Cloud coverage and height during FIRE ACE derived from AVHRR data. Journal of Geophysical Research: Atmospheres, 106(D14), 15215-15232. doi: 10.1029/2000JD900437. Cloud cover and height are derived from NOAA-12 and NOAA-14 advanced very high resolution radiometer (AVHRR) data taken over the Arctic Ocean for an 8° latitude by 30° longitude domain centered on the Surface Heat Budget of the Arctic Ocean (SHEBA) ship Des Groseilliers. Multispectral thresholds were determined subjectively and applied to each image, providing excellent temporal coverage during the May-July 1998 First ISCCP Regional Experiment Arctic Clouds Experiment (FIRE ACE). Mean cloud amounts were near 70% for the entire period but varied regionally from 55 to 85%. On the basis of a limited climatology of ship observations, these values appear to be typical for this part of the Arctic, suggesting that most of FIRE ACE was conducted in representative cloud conditions. A diurnal cycle of mean cloud amount was found for the domain during June and July having a range of 10% with a middle-to-late morning maximum. The AVHRR-derived cloud amounts are in good agreement with visual and radar measurements taken from the Des Groseilliers, except for a few subvisual and low cloud cases. Average AVHRR-derived cloudiness differ from the mean values obtained at the surface by −1 to +3%; this represents a significant improvement over previous satellite retrievals. The satellite-derived cloud heights are very accurate for most of the low cloud cases. Higher cloud altitudes are less certain because cloud optical depths were not available to adjust the temperature observed for the optically thin high clouds, and the radiating temperature of many of the high clouds is representative of some altitude deep in the cloud rather than the highest altitude level of condensate. The development of a more accurate automated algorithm for detecting polar clouds at AVHRR wavelengths will require inclusion of variable thresholds to account for the angular dependence of the surface reflectance as well as the seasonally changing albedos of the ice pack. The use of a 1.6-μm channel on the AVHRR, or other complement of instruments, will greatly enhance the capabilities for detecting clouds over poles during summer. 1640 Remote sensing; 0320 Cloud physics and chemistry; 3309 Meteorology and Atmospheric Dynamics: Climatology; 3349 Meteorology and Atmospheric Dynamics: Polar meteorology
Nordeen, M. L.; Minnis, P.; Doelling, D. R.; Pethick, D.; Nguyen, L.Nordeen, M. L., P. Minnis, D. R. Doelling, D. Pethick, L. Nguyen, 2001: Satellite observations of cloud plumes generated by Nauru. Geophysical Research Letters, 28(4), 631-634. doi: 10.1029/2000GL012409. A cloud plume is generated by the interaction of low-level easterly flow and diurnal surface heating on the island of Nauru in the tropical Pacific. Diurnal and seasonal cycles of cloud plume length, frequency, and heading were obtained by inspection of a year of hourly daytime GMS images. The cloud plume extends downwind and typically grows during the day to a mean length of 125 km by late afternoon with a maximum observed length of 425 km. The longest average plumes occur during March and April. The afternoon plume frequency was 63% compared to 50% for all observations. Further evaluation of the plume effects is needed to fully assess their impact on the development of long-term statistics of cloud and radiation parameters derived from surface instruments on the island's leeward side. 3360 Meteorology and Atmospheric Dynamics: Remote sensing; 3307 Meteorology and Atmospheric Dynamics: Boundary layer processes; 3322 Meteorology and Atmospheric Dynamics: Land/atmosphere interactions
Young, D. F.; Minnis, P.; Doelling, D. R.; Gibson, G. G.; Wong, T.Young, D. F., P. Minnis, D. R. Doelling, G. G. Gibson, T. Wong, 1998: Temporal Interpolation Methods for the Clouds and the Earth’s Radiant Energy System (CERES) Experiment. Journal of Applied Meteorology, 37(6), 572-590. doi: 10.1175/1520-0450(1998)037<0572:TIMFTC>2.0.CO;2. Abstract The Clouds and the Earth’s Radiant Energy System (CERES) is a NASA multisatellite measurement program for monitoring the radiation environment of the earth–atmosphere system. The CERES instrument was flown on the Tropical Rainfall Measuring Mission satellite in late 1997, and will be flown on the Earth Observing System morning satellite in 1998 and afternoon satellite in 2000. To minimize temporal sampling errors associated with satellite measurements, two methods have been developed for temporally interpolating the CERES earth radiation budget measurements to compute averages of top-of-the-atmosphere shortwave and longwave flux. The first method is based on techniques developed from the Earth Radiation Budget Experiment (ERBE) and provides radiation data that are consistent with the ERBE processing. The second method is a newly developed technique for use in the CERES data processing. This technique incorporates high temporal resolution data from geostationary satellites to improve modeling of diurnal variations of radiation due to changing cloud conditions during the day. The performance of these two temporal interpolation methods is evaluated using a simulated dataset. Simulation studies show that the introduction of geostationary data into the temporal interpolation process significantly improves the accuracy of hourly and daily radiative products. Interpolation errors for instantaneous flux estimates are reduced by up to 68% for longwave flux and 80% for shortwave flux.
