Effect of the Grell‐Freitas Deep Convection Scheme in Quasi‐Uniform and Variable‐Resolution Aquaplanet CAM Simulations

Abstract

Abstract The Grell‐Freitas deep convection scheme (GF) has been implemented in the Community Atmosphere Model (CAM) with the nonhydrostatic Model for Prediction Across Scales dynamical core. Aquaplanet simulations have been performed with a global quasi‐uniform resolution mesh with ∼120 km grid spacing and a variable resolution mesh employing a circular refined region with ∼30 km grid spacing centering at the equator and ∼120 km elsewhere. GF produces overall patterns of the general circulations comparable to those of other aquaplanet experiments, including those produced using the default Zhang‐McFarlane convection scheme (ZM) in CAM Version 5.4. GF alleviates the overestimated occurrence of weak intensity precipitation characteristic of ZM due to GF's different closure methods and deep‐convection trigger conditions. Compared to ZM, the GF characteristics of the equatorial Kelvin waves are closer to observations. GF also better simulates precipitation at variable resolution, with no unrealistic wave distortion by the refinement. Overall, GF shows less sensitivity of convective precipitation and heating/moistening tendencies to changes in horizontal resolution compared to ZM. However, vertically overlapped total cloud fraction simulated with GF in the tropics is more sensitive to the resolution than ZM due to the larger resolution‐sensitivity of high‐level cloud fraction in the tropics.

Keywords

• deep convection parameterization
• aquaplanet
• model resolution
• climate model