Environmental Controls Influencing the Relationship Between Atmospheric Rivers and Overshooting Convection: Insights from DCOTSS

Water vapor, a dominant greenhouse gas, is particularly important in the dry upper troposphere and lower stratosphere (UTLS) where even minor changes significantly impact climate. Previous studies link atmospheric rivers (ARs), filamentary moisture transport systems influencing North American climate, to overshooting convection in the North American Summer Monsoon region, especially in May and June. However, the specific role of ARs and their association with overshooting convection in the Midwest and Central U.S., and how they affect UTLS moisture during boreal summer, remains understudied.

AR-associated and non-AR-associated overshooting events differ in intensity and underlying dynamics. AR-associated events exhibit elongated, strong moisture transport from the Gulf of Mexico and low-level jets, while non-AR-associated events show more localized horizontal moisture transport and wind patterns. Primary lapse-rate tropopause altitude and patterns also vary. AR-associated overshooting typically develops ahead of an upper-level trough, whereas non-AR-associated overshooting tends to develop far from the trough near an upper-level ridge. Additionally, non-AR-associated cases exhibit stronger convective available potential energy (CAPE).

We will conduct case studies and composite analyses of these scenarios to examine how large-scale environmental controls influence their relationship with ARs. This analysis will use gridded radar (GridRad) overshooting products, ERA5 reanalysis data, and measurements from the Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) field campaign in 2021 and 2022, and climatological data. We will also investigate convective intensity and its impact on UTLS moisture during the North American Monsoon.