Evaluation of Convectively Coupled Rossby–Gravity Waves in a Field Campaign in Four Reanalysis Products

Convectively coupled equatorial waves are a significant source of atmospheric variability in the tropics. Current numerical models continue to struggle in simulating the coupled diabatic heating fields that are responsible for the development and maintenance of these waves. This study investigates how the diabatic fields associated with Mixed Rossby-Gravity (MRG) waves are represented in four reanalysis products by using a unique observational dataset from the TRMM (Tropical Rainfall Measuring Mission-Kwajalein Experiment) field campaign. The four global reanalyses include the ERA-Interim, Japanese 55-yar Reanalysis (JRA-55), Climate Forecast System Reanalysis (CFSR), and Modern-Era Retrospective Analysis for Research and Applications (MERRA).

We found that all four reanalyses captured the MRG structures in winds and temperature, and to a lesser degree in the humidity field except in the boundary layer. However, only the ERA-Interim and MERRA reanalyses captured the gradual rise and succession of the diabatic heating from boundary-layer turbulence, shallow convection, cumulus congestus, and deep convection within the waves. ERA-Interim is the only product that also captured the gradual rise of the subgrid-scale vertical transport of moist static energy. All reanalysis products underestimated the diabatic heating from cumulus congestus. Results provide observational basis on what aspects of MGR can be trusted and what cannot in the reanalysis products.