Modeling precipitation and cloud cellular structures in marine stratocumulus over the Southeast Pacific

Microphysical and meteorological controls on the formation of open and closed cellular structures in the Southeast Pacific are explored using high-resolution Weather Research and Forecasting (WRF) model simulations based on aircraft observations during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx). The effectiveness of factors such as boundary-layer moisture and temperature perturbations, surface heat and moisture fluxes, large-scale vertical motion and solar heating in promoting precipitation and open cell formation for given aerosol number concentrations is explored. For the case considered, precipitation and subsequent open cell formation respond very differently to boundary-layer moisture and/or temperature perturbations in a broad region than to perturbations embedded in closed cells. The local temperature perturbation drives a mesoscale circulation that prevents local precipitation formation but promotes it in a remote area. This represents a potential mechanism for the formation of Pockets of Open Cells (POCs) in the Southeast Pacific stratocumulus region whereby the circulation is triggered by strong precipitation in adjacent broad regions of open cells. Detailed results together with the diurnal cycle of precipitation and cloud cellular structures will be discussed.