Regional Comparisons of Precipitation and Diabatic Heating in Easterly Waves Undergoing Convective Amplification and Decay

Easterly waves (EWs) are synoptic scale tropical disturbances that can make large contributions to precipitation and diabatic heating in regions where they frequently occur across the global tropics. While the current body of work on EWs continues to explore the evolution of the precipitation characteristics and/or the processes involved in wave propagation for select regions, it is difficult to make meaningful comparisons between EWs occurring in different tropical regions and environments due to non-uniform data and methods across studies.

To address this knowledge gap and better understand the geographic variability in precipitation characteristics and processes related to EW propagation, we utilize a new objective feature tracking database produced by tracking global EWs from low-level curvature vorticity (CV) maxima. Since the CV features represent maximum values, each individual tracked point is associated with the wave trough occurring from wave genesis to lysis. By using the time-derivative of maximum CV, we document how precipitation changes as the wave trough undergoes patterns of strengthening and weakening.

Specifically, we composite precipitation data from 2000-2021 using IMERG and MERRA-2 and diabatic heating from the TRMM/GPM Convective-Stratiform Heating (CSH) and Spectral Latent Heating (SLH) v7 orbital products corresponding to times of amplification and decay of the tracked wave. The composites focus on four high EW track density domains that were found to have significant variability in the magnitude and structure of latent heating (and therefore precipitation) in EWs in previous work by the authors. In this work, we expect to find more intense rainfall and middle heavy heating profiles as the wave strengthens followed by lighter rainfall and more top-heavy profiles. We hypothesize that these result from the transition from deep convective to stratiform rain as the wave propagates and also anticipate finding considerable variability in this transition between regions. Time permitting, since the EWs contained within each of the four subdomains are inherently influenced by their unique surrounding environment, we also document changes in the environmental conditions associated with the strengthening and weakening of convection.