A Dynamical Model for the Shallow‐to‐Deep Transition of Amazonian Moist Atmospheric Convection

Abstract The development of deep convection and the timing of storm convection initiation over land are generally poorly represented by weather and climate models, probably due to the poor representation of the interaction between shallow and deep convection. The present work aims to present a prognostic model for the shallow‐to‐deep transition of Amazonian convection in which the shallow and deep clouds are described under a unified framework. Three types of clouds are considered in the present model: shallow cumuli, cumulus congestus, and deep cumulonimbus clouds. The model is based on the idea that the shallow‐to‐deep transition of atmospheric convection is primarily controlled by the interaction between updrafts and passive cloud volumes (non‐convective cumulus cloud volumes in the decaying stage) from which moist air can be entrained in the updrafts. In this framework, the cold pools accelerate the shallow‐to‐deep transition due to a larger cloud‐updraft interaction, allowing the updrafts to be less susceptible to entrainment of dry environmental air. A dynamical model for the diurnal cycle of shallow and deep is obtained and tested against idealized large‐eddy simulations. For idealized cases of Amazonian atmospheric convection, it is shown that the model represents the transition from shallow to deep convection reasonably well, showing that the model could lead to improvements in the forecast for storm convection initiation.