CR 60:147-162 (2014)  -  DOI: https://doi.org/10.3354/cr01229

ABSTRACT: To achieve the best climate simulation performance for a given area, the convection schemes of the area require examination. RegCM4, the latest version of a well-known regional climate model (RCM), was recently released with several improvements, including its representation of convection schemes. This new version employs 3 different convective schemes, and a major augmentation compared with previous versions of the model is its capability to simultaneously apply different convection schemes over the land and ocean, which is a configuration referred to as a mixed convection scheme. Here we tested all of the model-supplied convection schemes (version 4.1) in a 3 yr simulation. Model performances over East Asia (EA) and 4 sub-regions were evaluated. Our results showed that the 2 closure types in the Grell scheme produced different effects over EA, suggesting that the heating mechanism of buoyant energy is a key factor in this region. The Grell schemes, especially the Grell-AS scheme, tended to produce a dryer climate over the middle and lower reaches of the Yangtze River and southeastern China in the coarse resolution. Based on observations of the dynamics and microphysics of convection, the MIT scheme performed better than the often-employed idealization based on bulk-entraining plumes, but it tended to overestimate the water mixing ratio, leading to a wetter climate than the observations. The Kuo scheme showed relatively poor performance in the precipitation presentation in this region. Our results also showed that the mixed schemes can reduce the systematic cold bias of the model, and that the model performance can be significantly improved by increasing the model resolution.

KEY WORDS: Climate simulations · RegCM4 · Convection scheme sensivity · Regional climate · East Asia monsoon ·