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CERES/GEO and CERES-only(ERBE) LW Diurnal Averaging Comparison



CERES/GEO and CERES-only(ERBE) LW Diurnal Averaging Comparison(1)

  • CERES-only(ERBE) LW land temporal interpolation uses a half-sine and constant nighttime fit if the daytime LW flux is greater than the nighttime flux, to fill in 24 hourly time steps during the day
  • CERES-only(ERBE) LW ocean and snow temporal interpolation uses linear interpolation, to fill in 24 hourly time steps during the day. It is assumed that there are no LW diurnal cycles over clear-sky ocean and snow surfaces
  • CERES/GEO LW temporal interpolation uses all CERES and 8 3-hourly (GMT) GEO derived BB fluxes normalized at coincident CERES/GEO measurements to maintain CERES instrument calibration. All remaining hourly time steps are linearly interpolated between measurement times. For nonpolar regions there are usually 2 CERES and 8 GEO measurements, almost half the hourly time steps
Image: CERES/GEO and CERES-only(ERBE) LW Diurnal Averaging Comparison(1)
  • The CERES-only(ERBE) land LW half-sin fit models the daytime heating, which assumes symmetry about noon.
  • Note, that for a given daytime measurement, both a previous and following nighttime observation must be present to apply half-sine fit. If the conditions are not met linear interpolation between measurements are used, causing erroneous flux estimates.
  • It seems that the ERBE half-sine fit does not capture the daytime heating lag and nighttime cooling over land.

CERES/GEO and CERES-only(ERBE) LW Diurnal Averaging Comparison(2)

Image: CERES/GEO and CERES-only(ERBE) LW Diurnal Averaging Comparison(2)
  • CERES-only(ERBE) LW interpolation would show symmetry about noon or no difference between 16:30 and 7:30.
  • CERES/GEO clearly show the land afternoon convection (blue regions), which are colder in the afternoon than morning and daytime heating thermal lag (red regions), indicating land is warmer near sunset rather than sunrise.
  • Also the Peruvian stratus regions are warmer in the afternoon indicating the clear-sky ocean is warmer than the morning cloud tops
  • PM-AM differences can be ~ 30 W/m2

CERES/GEO and CERES-only(ERBE) LW Diurnal Averaging Comparison(3)

  • Difference of the monthly regional means of CERES/GEO and CERES-only temporal SW averaging for Terra (10:30 AM sun-synchronous) December 2002
Image: CERES/GEO and CERES-only(ERBE) LW Diurnal Averaging Comparison(3)
  • Terra-CERES-only monthly means are similar to the CERES/GEO LW temporal averaging because the daytime and nighttime LW biases cancel out.
  • CERES/GEO LW interpolation averaging reveals 3-hourly or 45° longitude striping due to discritization of the 3-hourly GEO measurements.
  • Global bias is +0.5 W/m2.

CERES Data Product Information

 
  Image: NASA Logo NASA Official: Dr. Norman Loeb
Page Curator: Edward Kizer
Page Last Modified: 10/16/2017 11:04:36 EST
Site Last Modified: 11/07/2017 17:18:43 EST