Modeling Interactions Between the Quasi-geostrophic Vertical Motion and Convection in a Single Column

A single-column-based framework that allows interactions between the large-scale quasi-geostrophic (QG) forcing and cumulus convections is developed. The framework parameterizes the large-scale vertical motion using the QG-omega equation, extending ideas developed in the tropics to subtropical and extratropical latitudes where the Coriolis effects are strong and the “weak temperature gradient” approximation is not active. Viewing the large-scale vertical motion as an internal variable of the coupled system, this framework allows a single-column or limited-area cloud-resolving model to be used to study the convection under varies large-scale perturbations and to parse its interaction with the forcings and feedbacks, thus assigning causality of the precipitation. Applying the modeling framework on two extreme precipitation events during the 2010 summer monsoon season in the Northern Pakistan, we show that the framework is useful for understanding the triggering and enhancement mechanisms of the extreme events.