Mesoscale organization in the Community Atmosphere Model (CAM)

Abstract:

Global climate simulations using CAM with horizontal resolution of 25 km begin to show interesting features that appear to be connected with mesoscale organization. These features include a reasonable climatology of tropical cyclones. Simulated precipitation in sub-Saharan West Africa is dominated by westward moving disturbances that show qualitative similarities to observations. Both the TCs and sub-Saharan disturbances appear to be dynamically-driven by resolved precipitation processes instead of parameterized convection. Disappointingly, simulations of propagating convection and related precipitation features in the US Midwest during summer are not significantly improved at 25 km resolution compared to 100 km resolution. This presentation will diagnose convective organization in CAM. Case-studies using nudging to re-analysis and regional-refinement over the US will be examined. These simulations will help to distinguish between errors due to large-scale forcing biases and those related to parameterization or dynamical deficiencies in CAM.