“结合法”表示的下垫温非均匀对夏季风气候影响的数值试验

用能较好表示陆面非均匀性且计算高效省时的"结合法"(马赛克法及统计-动力法解析表达型两者的结合),在区域气候模式RegCM2中BATSle方案内考虑下垫面附近各种温度、各种湿度的非均匀性,选用1991年夏季梅雨期实测资料,进行了模拟试验.与Giorgi针对暖季温度非均匀的单点独立试验结论不同,应用较线性概率密度函数(PDF)计算效率更高的余弦函数型PDF,发现总体上大气对陆面温度非均匀的响应是敏感的;与Giorgi结论类似,气候场对陆面湿度非均匀更为敏感,且其变化较有规律.可见,对夏季风气候的模拟能力可通过适当的温湿非均匀表示来提高.此外,其他结果也显示出单点独立试验的局限性,要反映陆气相互作用,耦合模式试验非常必要.

A Numerical Study of Effects of Land-Surface Heterogeneity in Temperature and Moisture from "Combined Approach"on Summer Monsoon Climate

The BATSle in regional climate model RegCM2, is treated with "combined approach" which is computationally effective to represent land surface heterogeneities in temperature and moisture, and is tested against real data of summer monsoon of 1991. Different from the results of the off-line simulations for warm season, we used a cosine probability density function (PDF), which is more effective in computation and different from the linear PDF applied by Giorgi. We can see, as a whole, that the summer monsoon climate is sensitive to the temperature heterogeneity. Similar to Ciorgi's result, the summer monsoon climate seems to be more sensitive to the moisture heterogeneity, which shows a regularity as changing with the heterogeneity. Therefore, the capability of simulations for summer monsoon climate may be improved via the appropriate representation of the heterogeneities in temperature and moisture. In addition, other results also reveal the limitations of off-line experiments, and that the coupling of the land surface scheme to the atmospheric model is very important and neces-sary for the studies on land-atmosphere interactions.