一次暴雨过程的变分同化试验及诊断分析
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作者单位
王顺凤,蔡春园,沈桐立  
基金项目:国家自然科学基金资助项目(40975037;40775033)
中文摘要:利用美国研制的WRF Var同化系统以及中国的云迹风资料,对2008年6月10日长江流域的一次暴雨过程做了三维和四维变分同化试验。试验结果表明:上述两种方案均能提高模式对大到暴雨预报的准确率,特别是四维方案在提高大暴雨的准确率方面表现更好,这是降水预报的重要方面;两个同化试验均能在一定程度上改善对要素场的预报,使用四维同化方案能够更有效地调整初始场、降低各要素场的预报误差。诊断结果表明:此次大暴雨过程是在高空低槽和低层切变线的共同作用下发生的,并有高、低空急流与之配合,具有较好的动力条件;低空的西南急流,不但为产生暴雨提供了所需的水汽输送,也为造成暴雨强对流所需的位势不稳定提供了必要的能量。
中文关键词:四维变分  资料同化  暴雨  云迹风
 
Variational assimilation and diagnosis of a rainstorm process
Abstract:Based on the WRF Var assimilation system developed by the U.S.and the cloud drift wind information of China,the three dimensional and four dimensional variational data assimilation is performed on a single case of heavy rain in the valley of Yangtze River on 10 June 2008.Results show that the two kinds of data assimilation of cloud drift wind can improve forecast accuracy in heavy rain and torrential rain.The four dimensional experiment scheme works particularly well in improving the accuracy of torrential rain.This is considered the most important in precipitation forecast.The further analysis of initialization of two assimilation tests shows that the assimilation of cloud drift wind can well improve the initialization,and has positive impact on the prediction of the physical variables.Overall,the use of four dimensional assimilative scheme can more effectively adjust the initial field,and reduce the forecasting errors of various elements.The causes of heavy rain are also discussed.Results show that this torrential rain process occurs under the combined effects of upper trough and low level shear line as well as the high low jet.The low level jet provides not only water vapor needed by the rainstorm,but also energy for positional instability of storm forming convection.
keywords:four dimensional variation  data assimilation  heavy rainfall  cloud drift wind
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