Linear response functions of shallow convection from Large Eddy Simulations and two parameterizations

Convective adjustments to perturbations in temperature, moisture, and momentum are important characteristics of moist convection and offer opportunities to better understand moist convection and to test convective parameterizations. Here, the linear response functions of a shallow cumulus ensemble to temperature and moisture perturbations are constructed for the Barbados Oceanographic and Meteorological Experiment case using Large Eddy Simulations. The instantaneous responses are dominated by responses to perturbations in the subcloud layer. For example, a warm anomaly in the lower half of the subcloud layer leads to rapid heating and drying at the cloud base, as well as rapid cooling and moistening of the trade inversion layer (hundreds of K/day or g/kg/day per 1K perturbation over a 100 meter layer), because of more updrafts penetrating through the convective inhibition layer at the cloud base. These strong tendencies illustrate the tight coupling between the subcloud layer and the cloud layer. On longer timescales (1-2 hours), the more familiar patterns start to emerge with distinct responses to perturbations in the subcloud layer, the convective inhibition layer, and the cloud layer. These responses are then compared with results from the combined University of Washington moist turbulence and shallow cumulus schemes and a shallow convection parameterization based on stochastically entraining parcels.