资源环境科技发展态势分析平台

The representation of the long-term radiative energy budgets in NASA's MERRA and MERRA-2 reanalyses has been evaluated, emphasizing changes associated with the reanalysis system update. Data from the CERESEBAFEdition 2.8 satellite product over 2001-15 were used as a reference. For bothMERRAand MERRA-2, the climatological global means of most TOA radiative flux terms agree to within; 3Wm 22 of EBAF. However, MERRA-2' s all-sky reflected shortwave flux is; 7Wm 22 higher than either MERRA or EBAF's, resulting in a net TOA flux imbalance of 24Wm 22. At the surface, all-sky downward longwave fluxes are problematic for both reanalyses, while high clear-sky downward shortwave fluxes indicate that their atmospheres are too transmissive. Although MERRA-2' s individual all-sky flux terms agree better with EBAF, its net flux agreement is worse (28.3 vs 23.3Wm 22 for MERRA) because MERRA benefits from cancellation of errors. Analysis by region and surface type gives mixed outcomes. The results consistently indicate that clouds are overrepresented over the tropical oceans in both reanalyses, particularly MERRA-2, and somewhat underrepresented in marine stratocumulus areas. MERRA-2 also exhibits signs of excess cloudiness in the Southern Ocean. Notable discrepancies occur in the polar regions, where the effects of snow and ice cover are important. In most cases, MERRA-2 better represents variability and trends in the global mean radiative fluxes over the period of analysis. Overall, the performance of MERRA-2 relative toMERRA is mixed; there is still room for improvement in the radiative fluxes in this family of reanalysis products.