中文摘要：

采用WRF及其耦合的NoahLSM陆面过程模式，通过对发生在2009年3月28日（个例1）和2010年5月6日（个例2）两次暴雨过程的24h模拟，研究了华南暴雨及中尺度对流系统（MCS）发展对初始土壤湿度（SM）的敏感性问题。首先采用源自NCEP-FNL和NASA-GLDAS的两种不同SM资料驱动模式进行对比试验，在此基础上，以NASA-GLDAS资料模拟结果为控制试验，通过不同程度（20％、600／0）增减初始SM开展多个敏感性试验。对比试验分析表明，两种资料应用对24h累积降水分布的模拟结果影响不大，但某种程度上可影响降水量的大小。预报技巧评分结果表明，采用NASA-GLDASSM资料进行模拟得到的结果比采用NCEP—FNLSM资料的模拟结果有所改进，尤其是50nli／1以上的暴雨预报，Ts评分最大可提高5％。敏感性试验分析发现，两次暴雨过程降水与SM之间主要呈正反馈作用，但其表现出的特征不完全相同。暴雨过程中MCS的组织发展形式对SM与降水之间的反馈作用有影响，具有午后局地降水性质、对流组织性发展较弱的个例1，SM增大仅引起微弱的降水增多，SM减少则明显导致降水强度减弱，降水对SM的减少更为敏感；而具有持续降水性质、对流组织性发展较强的个例2，降水对SM的增大更为敏感，SM增大可带来更明显的降水增多。此外还发现，对流系统不同发展阶段的这种反馈作用也存在差异，MCS组织性发展较弱的个例，强的反馈作用主要出现在对流发展初期阶段，而MCS组织性发展较好的个例，强的反馈作用则主要出现在对流系统发展后期。

英文摘要：

The impacts of soil moisture （SM） on heavy rainfall and the development of Mesoscale Convection Systems （MCS） are investigated through 24-h numerical simulations of two heavy rainfall events that occurred respectively on 28 March 2009 （Case 1） and 6 May 2010 （Case 2） over southern China. The numerical simulations were carried out with WRF and its coupling Noah LSM （Land Surface Model）. First, comparative experiments were driven by two different SM data sources from NCEP-FNL and NASA-GLDAS Secondary, with the run driven by NASA-GLDAS data as a control one, a series of sensitivity tests with different degree of （20%, 60%） increase or decrease in initial SM were performed to examine the impact of soil moisture on the simulations. Comparative experiment results show that the 24-h simulated cumulative rainfall distributions are not substantially affected by the application of the two different SM data, while the precipitation intensity is changed to some extent. Forecast skill scores show that simulation with NASA-GLDAS SM data can lead to some improvement, especially in the heavy rain （=〉 50 mm） forecast, where there is up to 5% increase in TS score. Sensitivity test analysis found that a predominantly positive feedback of SM on precipitation existed in these two heavy rain events, not with completely the same features Organization of the heavy rainfall-producing MCS seems to have an impact on the feedback process between SM and precipitation. For Case 1, the MCS was poorly organized and occurred locally in late afternoon, and the increase of SM only caused a slight enhancement of precipitation. Drier soil was found to result in an apparent decrease of rainfall intensity, indicating that precipitation is more sensitive to SM reduction. For Case 2, as the heavy rain was caused by a well-organized MCS with sustained precipitation, the rainfall is more sensitive to SM increase, which would bring more rainfall. Additionally, distinctive feedback effects were identified from different stages