| description abstract | The Clouds and the Earth?s Radiant Energy System (CERES) project uses two shortwave (SW) and two longwave (LW) algorithms to derive surface radiative fluxes on an instantaneous footprint basis from a combination of top-of-atmosphere fluxes, ancillary meteorological data, and retrieved cloud properties. Since the CERES project examines the radiative forcings and feedbacks for Earth?s entire climate system, validation of these models for a wide variety of surface conditions is paramount. The present validation effort focuses upon the ability of these surface-only flux algorithms to produce accurate CERES Edition 2B single scanner footprint data from the Terra and Aqua spacecraft measurements. To facilitate the validation process, high-quality radiometric surface observations have been acquired that were coincident with the CERES-derived surface fluxes. For both SW models, systematic errors range from ?20 to ?12 W m?2 (from ?2.8% to ?1.6%) for global clear-sky cases, while for the all-sky SW model, the systematic errors range from 14 to 21 W m?2 (3.2%?4.8%) for global cloudy-sky cases. Larger systematic errors were seen for the individual surface types, and significant random errors where observed, especially for cloudy-sky cases. While the SW models nearly achieved the 20 W m?2 accuracy requirements established for climate research, further improvements are warranted. For the clear-sky LW model, systematic errors were observed to fall within ±5.4 W m?2 (±1.9%) except for the polar case in which systematic errors on the order from ?15 to ?11 W m?2 (from ?13% to ?7.2%) occurred. For the all-sky LW model, systematic errors were less than ±9.2 W m?2 (±7.6%) for both the clear-sky and cloudy-sky cases. The random errors were less than 17 W m?2 (6.2%) for clear-sky cases and 28 W m?2 (13%) for cloudy-sky cases, except for the desert cases in which very high surface skin temperatures caused an overestimation in the model-calculated surface fluxes. Overall, however, the LW models met the accuracy requirements for climate research. | |
