CERES Edition 3 Cloud Retrievals

The Clouds and the Earth's Radiant Energy System (CERES) Project has developed an 10-year dataset of shortwave and broadband flux measurements matched with cloud properties retrieved from TRMM Visible and Infrared Scanner and the MODerate-resolution Imaging Spectroradiometer (MODIS) spectral radiances. These unique datasets, based on the CERES Edition-2 algorithms, have proven quite valuable for studying the role of clouds in climate and for improving and evaluating climate model simulations of clouds and radiation. With the availability of many other datasets, especially from surface-based and satellite-borne active sensors, it has become possible to improve and enhance the cloud retrieval algorithms to provide more accurate characterizations of the cloud 3-D structure and microphysical properties. These new techniques are being employed in the CERES Edition-3 processing, which begins in 2010. An improved cloud mask is used to detect more trade cumulus clouds and eliminate discontinuities between polar and non-polar areas. Errors in the earlier software are corrected to improve retrievals at high sun angles. A new cloud retrieval method based on CO2-absorption is combined with the Visible Infrared Solar-infrared Split-window Technique (VISST) to improve ice cloud height determination and to detect and retrieve cloud properties for multilayered clouds. New parameterizations are used to estimate cloud thickness and low-cloud heights to provide more accurate cloud boundaries in single-layer cloud conditions. Enhancements in cloud particle size retrievals and in polar retrievals are introduced. This paper summarizes the changes for Edition 3 and compares and contrasts the results with those from Edition 2, the original 10-year CERES dataset. Some independent validations using independent datasets are also presented. This new product from CERES will significantly enhance our understanding of the relationships between clouds and the Earth's radiation budget as well as provide the basis for a reliable record that will extend far beyond the initial 10 years of CERES data.