Moy, LA, Knuteson, RO, Tobin, DC, Revercomb, HE, Borg, LA, Susskind, J (2010). Comparison of measured and modeled outgoing longwave radiation for clear-sky ocean and land scenes using coincident CERES and AIRS observations. JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 115, D15110.
Clear-sky outgoing longwave radiation (OLR) is computed using the Atmospheric and Environmental Research (AER), Inc., Rapid Radiative Transfer Model (RRTM) for comparison with the observations of the Clouds and the Earth's Radiant Energy System (CERES) for both ocean and land scenes. CERES clear-sky OLR is in agreement with RRTM model calculations to 0.2% accuracy using best estimate radiosondes (BE) launched coincident with NASA Aqua overpasses at the Atmospheric Radiation Measurement Southern Great Plains (SGP) site and 0.8% using retrieved profiles of temperature, water vapor, ozone, and surface parameters from the Atmospheric Infrared Sounder (AIRS) on the Aqua platform. A partial flux analysis using AIRS radiances implies an accuracy for the RRTM model in the far infrared of 0.4% (about 0.5 W/m(2)) for wave numbers less than 650 cm(-1) (wavelengths greater than 15.4 mu m). CERES minus model biases over clear-sky ocean are similar to previously published results. Ordering the results according to the magnitude of the measured minus model mean bias for nighttime, tropical, ocean gives: +0.57 +/- 1.9 W/m(2) (Dessler/Fu-Liou), +0.83 +/- 1.5 W/m(2) (Huang/MODTRAN5), +1.6 +/- 1.6 W/m(2) (Moy/RRTM), +3.7 +/- 2.1 W/m(2) (Dessler/Chou). Comparison of observed minus modeled OLR over land are included in this study. Excluding nonfrozen ocean, a mean difference over land of +2.0 W/m(2) for nighttime cases and +1.0 W/m(2) for daytime cases is found where the land classes are weighted inversely by their standard error. The nighttime bias is quite consistent across all the land classes. The daytime bias shows less consistency with a tendency toward larger CERES minus AIRS RRTM OLR bias for the land classes with smaller vegetation fraction. Comparison of clear-sky CERES and AIRS RRTM OLR over cold snow-/ice-covered surfaces (mainly in the polar regions) is complicated by the use of the MODIS cloud mask in the identification of the clear CERES footprints used in the comparison. Clear scenes over cold surfaces can be identified more reliably in the daytime, for which the comparison between CERES and AIRS RRTM is better than 1.2 W/m(2) indicating good agreement.