Impact of resolution on the properties of tropical convection

We investigate the impact of resolution on the properties of tropical convection in idealized simulations. This is part of an effort to provide ways of understanding the limitations of moist processes in climate models (GCMs), by isolating the GCM dynamics and physics in doubly-periodic non-rotating simulations of radiative-convective equilibrium and then comparing with cloud-resolving simulations. We avoid subtleties of self-aggregation and convective organization by disabling cloud-radiative interactions and fixing the wind speed in the surface flux formulation.

This study is motivated by the observation that in the GFDL HIRAM model, strong radiative forcing in the upper troposphere destabilizes the atmosphere, leading to higher values of CAPE and more unstable temperature profiles. We use a cloud-resolving model at high (1km or less) and mesoscale (around 10-20km) resolutions to investigate if this behavior is robust, or if it is an artifact of the coarse resolution of the climate model. Our results seem to indicate that it is an artifact of the coarse resolution, which prevents the convection to efficiently bring back the atmosphere towards a moist adiabat. Comparing the properties of convection at high and mesoscale resolutions becomes more and more relevant to climate predictions, as some climate models are expected to reach mesoscale resolutions in the near future.