Mesoscale convective system activity in the United States under intermediate and extreme climate change scenarios

The importance of mesoscale convective systems (MCSs) and their precipitation is well-established, and any future spatiotemporal shifts in their frequency or intensity could have far-reaching societal impacts. This work describes how MCS activity in the conterminous United States east of the continental divide (ECONUS) is modified by two future climate change scenarios. For this study, MCSs are identified in output from a convection-permitting regional climate model (CP-RCM) for three 15-year periods—namely, a retrospective baseline (1990–2005) and two end-of-century (2085–2100) climate change scenarios based on RCP 4.5 (EoC 4.5) and RCP 8.5 (EoC 8.5). The data reveal an eastward shift in regional MCS activity. Annually, days with MCSs largely remain the same or decrease west of the Mississippi River, whereas areas east of the Mississippi River experience more MCS days and MCS precipitation. The largest seasonal increases in MCS days and precipitation occur during the spring in parts of the Midwest and Northeast, whereas the largest decreases occur in parts of the Southern Plains during the summer. Overall, EoC 8.5 produced larger regional changes compared to EoC 4.5, suggesting that future CP-RCM experiments could benefit from considering multiple climate change scenarios.