Sharpening Mesoscale Convective Systems Induced by Enhanced Moisture–Convection Feedback Over East Asia During 2000–2021

Abstract Changes in mesoscale convective system (MCS) spatial structure under climate warming are crucial, as steeper gradients combined with stronger storms significantly increase the risk of local record‐breaking rainfall events. However, mechanisms driving the changes in spatial structure remain unexplored. Here we examine changes in the spatial structure of observed summer MCSs over East Asia from 2000 to 2021, and find that the spatial structure of MCSs defined by hourly precipitation fields has become sharper, dominated by enhancement in heavy precipitation grid cells. The MCS‐maximum precipitation intensity increases at a rate of 16.7% decade −1 , contributed roughly equally by both the overall increase in MCS precipitation rates and the rising spatial sharpness. The observed sharper spatial structure arises from an enhanced moisture–convection feedback. Climate change during 2000–2021 intensifies synoptic moist static energy (MSE) forcing which stimulates enhanced shallow convection about 9 hr before MCS initiation. This enhanced shallow convection redistributes water vapor and ascents into heavy precipitation grid cells, thus sharpening MCS. Following MCS formation, intensified deep convection reinforces the mechanism, leading to a more pronounced sharpening of the MCS structure. The “stronger MSE and sharper MCS” mechanism identified here is tied to enhanced moisture–convection feedback, in which the increased convective latent heating peaks around 600 hPa before and during MCS life, and enhanced stratiform latent heating peaks around 400 hPa primarily during the development and maturation phases of MCS.