A Global Climatology of Tropical Easterly Wave Diabatic Heating Using Satellite and Reanalysis Data

Abstract

Tropical easterly waves (TEWs) play a critical role in regulating convection and precipitation across the global tropics. These synoptic-scale features are commonly known to act as seed disturbances for tropical cyclogenesis and serve as an essential component in monsoon precipitation. Since tropical waves such as TEWs are known to produce large amounts of rainfall and diabatic heating that can strongly affect the large-scale circulation and extratropical weather, better understanding the convective behavior of these waves could lead to more accurate weather forecast and global climate models. To help improve our knowledge of a more elusive type of tropical wave, we use satellite and reanalysis estimates of the diabatic heating associated with and specific to TEWs identified by a tracking algorithm based on low-level curvature vorticity. This study uses the Tropical Rainfall Measuring Mission (TRMM) version 6 convective-stratiform heating (CSH) and spectral latent heating (SLH) orbital products to create a global climatology (1998-2015) of TEW diabatic heating. Additionally, the observed heating is compared to similar terms using the MERRA-2 temperature tendency data. TEW-specific composites of the vertical structure of diabatic heating and its subterms are compared across datasets and across a variety of tropical regions. There are striking differences between the reanalysis and satellite heating with the reanalysis overpredicting the magnitude of heating, especially at low levels. The observed heating profiles show stronger mid-level heating, although both reanalysis and observed heating profiles show increases in mid-level heating for the conditional (i.e., TEW-specific) heating relative to the unconditional background. Similar patterns of top- and bottom-heaviness emerge in two-dimensional composites of TEW latent heating as stronger heating rates and percent contributions to the background are generally higher at 500 hPa than at 850 hPa. Geographic differences in the strength and distribution ofdiabatic heating, inter-term and dataset comparison, and preliminary work towards identifying wave-to-wave and seasonal variability are also discussed.