Assessment of MERRA-2 Land Surface Energy Flux Estimates

AbstractIn the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) system the land is forced by replacing the model-generated precipitation with observed precipitation before it reaches the surface. This approach is motivated by the expectation that the resultant improvements in soil moisture will lead to improved land surface latent heating (LH). Here we assess aspects of the MERRA-2 land surface energy budget and 2 m air temperatures (T2m). For global land annual averages, MERRA-2 appears to overestimate the LH (by 5 Wm−2 ), the sensible heating (by 6 Wm−2), and the downwelling shortwave radiation (by 14 Wm−2), while underestimating the downwelling and upwelling (absolute) longwave radiation (by 10-15 Wm−2 each). These results differ only slightly from those for NASA’s previous reanalysis, MERRA. Comparison to various gridded reference data sets over Boreal summer (June-July-August) suggests that MERRA-2 has particularly large positive biases (>20 Wm−2) where LH is energ...

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