Weak Temperature Gradient Modeling of Convection in OTREC

Convection observed in the OTREC field program in the tropical east Pacific and southwest Caribbean is simulated using a cloud-resolving model employing the weak temperature gradient approximation. Simulations are made using reference profiles derived from three-dimensional variational analyses of dropsonde data selected for different ranges of saturation fraction, a kind of column relative humidity. For each of these humidity ranges, two simulations are performed, one with ventilation of the model domain by the ambient wind (a new model feature) and one without this ventilation. The model results using ventilation are much closer to observation than those without ventilation, especially for drier environments. These results have strong implications for the distribution of ITCZ convection in the east Pacific and for the construction of cumulus parameterizations.