On the consistency of CERES longwave flux and AIRS temperature and humidity profiles

Abstract

In this paper, the temperature and humidity profiles from the Atmospheric Infrared Sounder (AIRS) are evaluated with outgoing longwave radiation (OLR) from the Clouds and the Earth's Radiant Energy System (CERES) measurements. Using collocated CERES and AIRS measurements from A-train observations, the temperature and humidity profiles from the AIRS are evaluated by using them in a radiative transfer model and comparing the modeled OLR with that from the CERES. Both the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) measurements are used to ensure a strict clear-sky condition over the CERES fields-of-view (FOVs) in the evaluation. The paper shows that model-computed OLRs using the AIRS temperature and humidity profiles and surface skin temperature agree well with CERES data for daytime oceans, indicating good accuracies of both the AIRS and the CERES products. However, it is found that a certain discrepancy exists between OLR from the modeling with the AIRS atmospheric profiles and that from the CERES measurements. For nighttime oceans, the AIRS temperature and humidity profiles and surface skin temperature likely have significant bias errors in tropical and subtropical areas that are due to undetected thin cirrus clouds. The inconsistency of the CERES and the AIRS product in OLR needs to be understood for reliable earth radiation studies. Copyright 2011 by the American Geophysical Union.