Observed and Simulated Mesoscale Convective Systems over High Mountain Asia. Part II: Past Trend and Future Projection

In the second half of this two-part study, we apply a mesoscale convective system (MCS) tracking method to two satellite datasets, together covering nearly four decades the longest observational MCS record to date over High Mountain Asia (HMA). Using this dataset, we examine past trends of warm-season MCS characteristics and their environmental drivers. A consistent decreasing trend in MCS frequency is found during 1985-2023. Analysis of dynamic and thermodynamic variables indicates increasing convective inhibition (CIN), which represents the energy barrier to convective initiation, as the primary driver of this trend. Enhanced CIN modulates the convective population by suppressing weaker convection, which is common over HMA, while favoring fewer but stronger convective systems. We further leverage simulations from a high-resolution global climate model and a global storm-resolving model to assess MCS responses to global warming. Both models consistently project continued reductions in MCS frequency under warmer conditions, suggesting a sustained downward trend in future climates. Changes in MCS-related precipitation are more nuanced, reflecting a balance between reduced MCS frequency and increased precipitation intensity per event. These fndings provide a multidecadal perspective on the evolution and projected response of MCSs over HMA, highlighting the critical role of CIN in regulating convective organization and the potential for rarer but more intense storms to amplify hydrological and societal risks in a warming climate.