Multiple‐instance superparameterization, part 2: the effects of stochastic convection on the simulated climate

Abstract/Summary

The cloud-permitting model (CPM) of the super-parameterized Community Atmosphere Model (SP-CAM) is a stochastic parameterization. As reported in a companion paper, we have created a variant of SP-CAM, called MP-CAM, that uses the averaged feedback of ten independent two-dimensional CPMs in each global model column, in place of the single CPM of SP-CAM. This ensemble-averaged feedback is interpreted as an approximation to the feedback from a deterministic parameterization. We present evidence that MP-CAM is indeed more deterministic than SP-CAM. The climates of the SP and MP configurations are compared, giving particular attention to extreme precipitation events and convectively coupled large-scale tropical weather systems, such as the Madden-Julian Oscillation (MJO). A number of small but significant changes in the mean-state climate are uncovered, and the deterministic parameterization slightly degrades the MJO simulation.