8.6    CWRF Improved Rainfall Prediction by Ensemble Cumulus    Parameterization

Liang, Xin-Zhong,  Department of Atmospheric and Oceanic Science, University of Maryland at College Park, Fengxue Qiao, Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, and Georg Grell, Earth System Research Laboratory, Global Systems Division, NOAA

The CWRF, a Climate extension of the WRF, has been developed with an ensemble cumulus parameterization (ECP) to predict convective rainfall variations under a wide range of regional climate regimes. The ECP has been built upon and improved from the G3 scheme (Grell and Dvˇnˇyi 2002 with updates). In particular, the coding structure has been changed to facilitate independent selections of a cumulus closure suite for each of ocean, land and coastal zone, and also specifications of weights of individual members in each suite. This study will test the ECP performance relative to other cumulus schemes. We will demonstrate that, among the 12 widely used cumulus schemes incorporated in the CWRF, the ECP most realistically reproduce the summer rainfall geographical distributions observed in 1993 and 2008. This success results mainly from the use of separate choices of closure algorithms with appropriate weights. Specifically, the mass convergence closure works best over land and the CAPE tendency closure performs better over ocean, while the combination of the two is more desired over the coastal zone.

 

For presentation at the 13th WRF UsersÕ Workshop, National Center for Atmospheric Research, Boulder, Colorado, 25-29 June 2012. This work was supported by the NOAA Education Partnership Program (EPP) COM Howard University 00073421000037534 and Climate Prediction Program for the Americas (CPPA) NA11OAR4310194 and NA11OAR4310195. The model simulations were conducted at the NOAA/ESRL and UIUC/NCSA facilities.