HAMSR, APR-3, and GPM Observations During NASA CPEX Campaigns for the PBL Thermodynamic Structures to Understand the Development of Tropical Convective Systems

The ability of microwave sounder to obtain temperature and moisture profiles at high spatial resolution under cloudy conditions is essential for understanding development of convective systems. HAMSR, a microwave sounder, was mounted on the NASA DC-8 aircraft during NASA CPEX-AW (2021 August-September) and CPEX-CV (2022 September) campaigns and measured the temperature and specific humidity profiles in both clear and cloudy conditions when the aircraft flied through convective systems in the tropical Atlantic. The HAMSR measurements are also collocated with NASA GPM/IMERG precipitation rate estimates, APR-3 radar reflectivity measurements, and MERRA-2 moisture transport parameters to provide a thorough picture of how atmospheric thermodynamic conditions, cloud structures, and moisture transport in and around convective systems influence the systems’ development and propagation. We use the HAMSR temperature and moisture profiles to calculate buoyancy profiles at the front and wake of tropical convective systems, including convection associated with a hurricane and African Easterly Waves, and establish how buoyancy profiles are related to the GPM-based estimates of precipitation development. The APR-3 radar reflectivity profiles can further inform the structures of clouds related to the HAMSR humidity profiles. The HAMSR retrieved humidity profiles are consistent with those retrieved from the HALO lidar measurements and dropsondes. Before the onset of precipitation, couplets of dry/moist anomalies with nearby cold anomalies in the PBL are stronger in the front of convective systems than the wake, reducing negative buoyancy in the PBL and weakening the convective inhibition. Such couplets are less rigorous in the fronts of weakly precipitating, under-organized storms. Consequently, such mechanism favors a thermodynamic condition of convective initiation in the front of the strongly precipitating systems, and the systems propagate into the front direction by generating new convection.