Evaluating near-storm environmental moisture relative to tropical deep convection growth using CPEX-CV airborne data

Abstract

Mesoscale convective systems (MCSs) associated with African easterly waves (AEWs) that propagate and intensify over the tropical East Atlantic may serve as precursors for tropical cyclones. Previous studies utilizing satellite- and reanalysis-based data emphasized that deep convective growth over tropical oceans favors moister environments, including near the AEW trough. However, limitations in those dataset’s spatial and temporal resolution lead to remaining unknowns of the interaction between near-storm environmental parameters with convective lifecycle in this oceanic region. The NASA DC-8 research aircraft, based out of Sal Island during September 2022 for the Convective Processes Experiment-Cabo Verde (CPEX-CV), was equipped with an airborne precipitation radar, Doppler wind lidar, microwave sounding radiometer, and dropsondes to measure near-storm environmental conditions related to deep convection over the tropical East Atlantic. Using this airborne data, this study evaluates the relationship between moisture and deep convective growth and sustainability over this region. Relative humidity (RH) was averaged over defined low-, mid-, and upper-levels with respect to a growing deep convection system sampled with multiple passes during CPEX-CV Research Flight 7 on 16 September 2022. These aircraft observations, supplemented with a geostationary satellite-based MCS tracker and reanalysis data, showed mid-tropospheric moistening supporting continued growth and maintenance of the convective system in RF7 after the flight while propagating in phase with the AEW. In comparison, CPEX-CV Research Flight11 sampled a convective system located southwest of a wave trough and in a relatively drier environment closer to the West African coastline that dissipated after the flight. Future work will analyze additional key environmental parameters (i.e., vertical wind shear, column saturation fraction) from CPEX-CV airborne observations, reanalysis, and satellite-based data to better understand why the convection in RF11 did not sustain and which environmental factors contributed to the ultimate dissipation of the convection in RF7.