The Radiation Fluxes of NCEP/Climate Forecast System Reanalysis Validated with NASA/CERES

Newly produced NCEP/Climate Forecast System Reanalysis (CFSR) is the first reanalysis using a coupled ocean-land-atmospheric model in the data assimilation system. The CFSR provides a new data base from 1979 through 2009 for studying climate variability. Also, the CFSR provides the initial conditions for conducting re-forecasts, which is essential for calibrating future seasonal forecasts in operations. In addition, this long data set is suitable for other researches and assessments. The longwave (LW) and shortwave (SW) radiation modules in the CFSR coupled model are modified codes originally from AER's RRTMG-LW v2.3, and RRTMG_SW v2, respectively. This paper will present the basic properties of the CFSR earth radiation budget, and comparisons to observations and products from NASA Clouds and Earth's Radiant Energy System (CERES) for the period from March 2000 to October 2005.

Preliminary results show substantial improvements from the previous NCEP/NCAR and NCEP/DOE Reanalyses. On the surface, the CFSR-CERES difference in downward SW is about 2% for the global mean, albeit larger systematical differences in certain geographical regions. Both the upward and downward components of LW are in very good agreements within the observational errors. At the TOA, the agreement of all-sky OLR is within 2% with positive bias, and clear-sky OLR difference is about 0.6% with negative bias. The TOA all-sky reflected SW is biased negative slightly, but positive up to 5% for clear-sky.

These results imply that the model cloud, which is physically thin but optically thick, could be biased low in altitude. Other details regarding to the geographical distributions, seasonality, and data related attributes will be further discussed.