Validation of a Technique for Estimating OLR with the GOES Sounder

In order to eventually use the capability of the Geostationary Operational Environmental Satellite (GOES) Sounder to capture the diurnal signal of outgoing longwave radiation (OLR), it is necessary to establish its instantaneous accuracy. Error characteristics of OLR derived from the GOES Sounder are analyzed using Clouds and Earth's Radiant Energy System (CERES) observations. The comparisons are based on over 28 000 data collected in July 1998 and April 2000 over the continental United States. The July data correspond to observations from GOES-8 and -9 and the CERES instrument on board the Tropical Rainfall Measurement Mission (TRMM) satellite. The April data correspond to GOES-8 and -10, and two CERES instruments on board the Terra satellite. The comparisons are for instantaneous, homogeneous scenes of 1 degree * 1 degree boxes. Comparisons of GOES Sounder with collocated TRMM and Terra CERES OLR show instantaneous rms agreement to within about 7 W m2 for day and/or night homogeneous scenes. The GOES technique explained over 91% and 96% of the variance of CERES observations for both night and day, and for both land and ocean scenes for July 1998 and April 2000, respectively.