Title: Top-of-atmosphere and surface radiation budget from CERES

 

Speaker: Seiji Kato

 

Climate Science Directorate, NASA Langley Research Center, Hampton, Virginia, USA.

 

Clouds and the Earth's Radiant Energy System (CERES) instruments on Terra and Aqua have been taking broadband radiance measurements since, respectively, March 2000 and July 2002. Collocation of CERES footprints with Moderate Resolution Imaging Spectroradiometer (MODIS) pixels and cloud properties derived from MODIS radiances allow us to build angular distribution models by scene type of CERES footprints. Scene type dependent angular distribution models minimize the error in a time series of regionally or globally averaged top-of-atmosphere (TOA) irradiances caused by, for example, variability of cloud cover. The irradiance at the surface also can be computed with cloud and aerosol properties derived from MODIS. With these TOA and surface irradiances, we are able to understand spatial and temporal variability of TOA, surface, and atmospheric radiation budget. CERES data show that interannual variability of TOA global mean irradiances is remarkably small compare to the mean value. I will try to explain the reason for small interannual variability of the global mean TOA irradiance. In addition, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat have been providing the vertical profile of cloud and aerosols since July 2006. In this talk, I will also explain how cloud vertical profiles derived from CALIPSO and CloudSat data improve the estimate of atmospheric radiative heating rates and potentially improve the estimate of the global surface radiation budget. A recent estimate of the global and annual mean downward longwave irradiance at the surface by Trenberth et al. (2009) is 333 Wm^-2. Their downward longwave estimate appears to have a largest discrepancy, among components of the surface irradiance, compared to that estimated from satellite data. In describing a possible improvement of the surface irradiance estimate in this talk, therefore, I will primarily focus on the downward longwave irradiance.