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 waves (MRGs) are represented in four reanalysis products by using a unique observational dataset from the TRMM‐KWAJEX (Tropical Rainfall Measuring Mission‐Kwajalein Experiment) field campaign. These reanalyses include ERA5, Japanese 55‐year 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 ERA5 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. ERA5 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 MRG can be trusted and what cannot in the reanalysis products.
This content will become publicly available on April 16, 2025
Tropical easterly waves (TEWs) are a recurrent mode of low‐latitude weather that are often convectively coupled and impact precipitation extremes. Previous work has examined the development of TEWs and their associated precipitation for individual seasons or regional domains, but no studies exist that document the importance of TEW precipitation globally. This study quantifies the precipitation associated with TEWs across the entire tropics using satellite (Integrated Multi‐satellitE Retrievals for the Global Precipitation Measurement [IMERG]) and reanalysis (Modern‐Era Retrospective analysis for Research and Applications, Version 2 [MERRA‐2]) data. Traditional space‐time filtering of precipitation reveals a mostly similar climatological power distribution for westward traveling, synoptic period disturbances corresponding to TEWs within all data sets. Using objective tracking, we find that areas with maximum TEW frequency such as the North Atlantic, Equatorial Pacific, and Indian Ocean have the highest accumulation of TEW‐associated precipitation. TEWs account for at most 30% of total annual precipitation in regions where they commonly occur and 1%–5% over much of the tropics. Vertically collocated storms, where the 850 and 700 hPa tracks correspond with each other, have higher conditional rain rates and indicate that waves with vertical development produce stronger and more organized convection. We find similar regional patterns using MERRA‐2 precipitation and latent heating, although the importance and contribution of TEWs to the background are reduced compared to IMERG. While the broad pattern of TEW associated precipitation in MERRA‐2 is like observations, the underestimation of rainfall contributions from TEWs, coupled with occasional false alarms in reanalysis data, suggests that MERRA‐2 does not capture organized convection within TEWs correctly.
more » « less- Award ID(s):
- 1944177
- PAR ID:
- 10512515
- Publisher / Repository:
- AGU
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 129
- Issue:
- 7
- ISSN:
- 2169-897X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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