Modulation Effects of Atmospheric Environmental Conditions on Mesoscale Convective Systems over Tropical Oceans

Huaiping Wang, Qiu Yang

Mesoscale convective systems MCSs play a central role in tropical rainfall and are closely linked to extreme precipitation and large scale variability. However, a quantitative understanding of their environmental controls remains incomplete. In this study, we construct an observational MCS dataset by applying an objective tracking algorithm to satellite and reanalysis data, and examine the climatology of tropical MCSs. We further use a Random Forest model to quantify environmental controls at the monthly scale. The results show pronounced spatial and seasonal variability in tropical MCS activity, closely tied to large scale circulation and moisture availability. Environmental predictors explain up to about 50\% of the variance in monthly MCS frequency and associated precipitation. Moisture convergence atmospheric instability and column integrated water vapor emerge as the leading controlling factors. Partial dependence analyses reveal clear nonlinear interactions among key predictors. The relative importance of environmental controls also varies with region and season, with thermodynamic factors dominating in some regimes and dynamic factors such as vertical wind shear playing a larger role in others. Overall, this study provides an observationally constrained quantification of environmental controls on tropical MCSs and offers new insight into their variability and potential response to climate variability and change.