A Novel Method for Discerning the Contributions of Shallow and Deep Convection in the Evolution of Tropical Cyclones in Model Simulations, with Implications for Use with Satellite Observations

Convective storms, particularly tropical convective systems, are major contributors to Earth's rainfall and play a crucial role in transporting heat and moisture from the surface to the upper troposphere. Their influence extends to modifying atmospheric circulation, impacting Tropical Cyclone (TC) genesis, and facilitating phenomena such as Madden-Julian Oscillation (MJO) and ENSO events. However, the fundamental factors driving the development and growth of convective storms remain a significant and unanswered question. This study investigates the factors contributing to the development of deep convection by analyzing the relationship between the vertical velocity and the observables precipitation and near-surface wind divergence using geophysical variables that are readily available in model simulations. The connection between near-surface convergence/divergence and vertical transport has long been touted as essential to understand the process of moist convection but has never been objectively quantified. To examine this relationship, we utilized output data from three WRF Single-Moment Microphysics Scheme (WSM6) experiments, simulating the 2005 category-5 Hurricane Rita with three different assumptions of the Particle Size Distributions (PSDs), as detailed in the study by Hristova-Veleva et al. (2021). These experiments employed distinct microphysical processes, influencing latent heating and thereby shaping the evolution of convection and the intensity of the storm. The analysis introduces a novel technique that delineates four types of vertical structures for precipitating regions, through the correlation of vertical velocity with near-surface divergence and total condensate precipitation. This method results in a classification of four well-recognized convective precipitation structures – shallow convection, deep convection, stratiform precipitation and anvil regions. The classification performs consistently across varying simulations of Hurricane Rita's structure, intensity, and evolution. Furthermore, we investigate the role of deep convection and its spatial distribution in the evolution of TCs. Our findings reveal that model-simulated TCs intensify when significant deep convection develops near the storm center and weaken when deep convection occurs farther away. These findings are consistent with observational and modeling TC studies.