Sensitivity of Convective Organization Parameterization in CAM5 to Spatial Resolution

Description

This study investigates the role of convective organization at various spatial resolutions, using a unique parameterization of convective organization, org, as a prognostic variable in the Community Atmosphere Model. A unified shallow+deep convection scheme (a N-plume version of the University of Washington shallow convection scheme, currently with N=2 in most of our experiments) has org governing the properties and relative contributions of the plumes. Rain evaporation is the main source of convective organization, and the functions of organization within a plume ensemble include 1) plume radius enhancement (entrainment rate reduction) 2) the plume coverage (area or mass) that reaches the Level of Free Convection, and 3) the probabilities of overlap, and thus interactions, between plume ensemble members. Following from previous works (Mapes and Neale 2011), we test the feedback of convective organization at different spatial resolutions (2-deg, 1-deg, and variable-resolution [Zarzycki & Jablonowski, 2014] grid) to probe, and try to improve, simulations of regional climate systems such as South Asian Summer Monsoon. In addition, we compare our simulations with CAM-UNICON - the CAM simulations that use the Unified Convection scheme (UNICON [Park 2014a; Park 2014b], a candidate parameterization for the upcoming CAM5.5) to replace the default shallow and deep convection schemes - to seek a step toward resolution-independent parameterization of convection.