Stochastic Multicloud Model (SMCM) Implemented NCEP Climate Forecast System Version 2 (CFSv2): Sensitivity to the Middle Tropospheric Moisture Parameter in the SMCM

A stochastic multi-cloud model (SMCM) convective parameterization is incorporated in the National Centers for Environmental Predictions' Climate Forecast System version 2 (CFSV2). The resulting model is referred to here as CFSsmcm. Two 15 year long climate simulations of the CFSsmcm, differing only by one SMCM parameter, namely, the mid-tropospheric dryness parameter, MTD, are analyzed here. This particular parameter is chosen not only because it plays a crucial role in the SMCM formulation, but also is observed to be critical for triggering tropical convection. In one case we have used a single homogeneous MTD value for the entire globe and in the other run two different MTD values are used for land and ocean. The global precipitation climatology significantly improves in the inhomogeneous MTD case without significantly affecting the excellent performance of the CFSsmcm in terms of the intra-seasonal and synoptic variability.