Sensitivities of explicity simulated tropical cloud ensembles to their large-scale setting

A cloud-resolving model is used to probe the sensitivities of tropical convective cloud ensembles to their large-scale setting. Our strategy is to impose vertically coherent perturbations in temperature and/or moisture (like those produced by large-scale wave motions) and then measure the response of the convection. Results show that convection is especially sensitive to perturbations imposed at low-levels, with the sense of the response being consistent with expectations based on simple parcel theory. Surprisingly, however, the depth of the convective heating response is found to be essentially non-deterministic. By this we mean that two otherwise identical simulations with slightly different initial conditions can exhibit dramatically different deep-convective responses to the imposed perturbations. Possible reasons for this will be discussed.