Changes in Mesoscale Convective System Precipitation Structures in Response to a Warming Climate

Mesoscale convective systems (MCSs) play an important role in the hydrological cycle and often produce flash floods. Given their significant impact, it is crucial to comprehend how they will change under a warming climate. This study uses a satellite- and radar-based MCS tracking algorithm on convection-permitting climate model simulations and examines the changes in MCS properties–including occurrence frequency, duration and propagation speed–and precipitation structures between the historical and future simulations. Increases in MCS frequency and total warm season precipitation is observed in pseudo-global warming, and the increase is more noticeable over the southern parts of the U.S. The precipitation intensity and precipitating area generated by future MCSs also rises and results in an increase in precipitation volume. MCS precipitation structures are further classified into convective core and stratiform regions to understand how change in these structures contribute to future rainfall changes. In a warmer climate, the stratiform region demonstrates little to no change in size, but increases in mean precipitation rate and mean maximum precipitation rate by 15% and 29% are noted, respectively. Meanwhile, a more robust future response is observed in the convective core region, with its size, mean precipitation rate and mean maximum precipitation rate increasing significantly by 24%, 37% and 42%, respectively. Both convective and stratiform components show a lowered frequency in light and an increased frequency in moderate to heavy precipitation, suggesting that there could be a higher percentage of intense MCSs in a warmer climate. The increase in the upper limit of maximum convective core rainfall rate also suggests the most intense MCSs are likely to become stronger in the future. By examining the environmental properties of MCS initial condition, the future intensification of convective rain could be attributed to a combined effect of substantial increases in the atmospheric instability and moisture availability.