Impact of Aggregational Growth Modeling on the Intensification of Extreme Tropical Cyclones Through Radiative Feedbacks

ABSTRACT The sensitivity of tropical cyclone (TC) intensity to cloud microphysical processes is investigated using large‐ensemble simulations with a global high‐resolution climate model for five recent cases of extremely intense TCs. This study focuses on the aggregational growth of ice particles, which strongly depends on the representation of the collection kernel and affects the extent of upper‐level clouds. The ensemble experiments demonstrate that a more accurate treatment of the collection kernel leads to a statistically significant increase in TC intensity compared with a simplified scheme. The modification enhances known radiation‐convection interactions that favor TC intensification: a sharper horizontal gradient of longwave cloud‐radiative forcing near the eyewall suppresses rainbands beyond the radius of maximum wind, thereby weakening their inhibition of angular momentum supply into the TC core and intensifying the TC. Therefore, mass exchange among cloud ice, snow, and graupel—modulating upper‐level cloud‐radiative forcing—plays a key role in achieving a more realistic simulation of TC intensity.