African Easterly Waves in the Superparametrized Community Atmosphere Model (SP-CAM)

This study examines African easterly wave (AEW) dynamics in the Superparameterized Community Atmosphere Model (SP-CAM). Conventional general circulation models (GCMs) typically have difficulty representing AEW dynamics over West Africa. One reason is that the coarse resolution of these models limits their ability to represent the multi-scale interactions between the large-scale dynamics and individual convective systems, which are important for the origin and development of AEWs. The SP-CAM has been designed to better simulate the interactions between small-scale circulations and large-scale dynamics, by replacing the conventional parameterizations with a 2D cloud resolving model embedded within each GCM grid column. With this approach we are able to capture the interactions between clouds and the global circulation of the atmosphere. We have performed a 20 year AMIP-style run covering the years 1991-2010 using SP-CAM version 3.5, which uses the finite-volume dynamical core. This simulation was designed to investigate the influence that resolved convection has on the dynamics of the West African monsoon. Preliminary results show that while the standard CAM exhibits little to no AEW activity over the entirety of the simulation, SP-CAM on the other hand does appear to represent AEWs with the same frequency, amplitude and phase speed as is observed. This study provides an analysis of AEW activity in the SP-CAM using two distinct methods: 1) Composite wave analysis using synoptic techniques of tracking trajectories of dynamical fields and 2) Space-time filtering techniques that are used to characterize the typical AEW disturbance in the model. The goal of our work is to improve our understanding of the multi-scale interactions that occur between AEWs and convection over West Africa.