中文摘要：

为了改善低纬高原地区天气预报水平,利用WRF（Weather Research and Forecasting）模式及其变分同化系统进行雷达VAD（Velocity Azimuth Display）反演风场资料同化试验。通过设计不同的试验方案,对2009年6月30日00：00至7月1日00：00发生在云南的一次强降水过程进行数值模拟和对比分析,结果表明：同化VAD反演风场资料后对区域模式的风矢量初始场有明显影响。同化系统能把雷达反演风场信息有效地引入模式初始场,改善强降水区域的水汽输送和风场辐合强度;同化VAD反演风场资料后对区域模式累计降水预报有一定改进作用。从长时间累计降水量定量检验结果看,具体表现为25mm以上量级的降水准确率明显提高、漏报率下降,预报偏差更趋合理。不同的同化试验方案之间的模拟结果差异较大。同化频率越高、同化持续时间越长,对区域模式初始场和预报场的影响越明显。但同化持续时间不宜过长,否则可能导致系统移速过快、降水强度偏大、空报率增加等异常。

英文摘要：

In order to improve the weather forecast quality over the low-latitude plateau regions, the wind data retrieved with VAD （Velocity Azimuth Display） method are assimilated to the WRF （Weather Research and Forecasting） model by WRF-3DVar （3 Dimensional Variational Data Assimilation System）. With different assimilation schemes, a torrential rain event occurred in Yunnan Province from 00：00UTC 30 June 2009 to 00：00UTC t July 2009 is numerically simulated and comparatively analyzed. The results indicate that the initial wind fields of the WRF model are markedly improved by assimilating the retrieved wind data. The WRF-3DVar can availably introduce the information of the retrieved wind to the initial conditions of the regional numerical model. The assimilation of the retrieved wind data helps enhance the wind convergence and vapor transportation over the rainy area. Furthermore, the assimilation help improve quantitative precipitation forecasts. The quantitative test of the 18-hour rainfall forecast shows that forecasts are more accurate, less pretermissions, and more rational pertinence for over 25.0 mm precipitation in the assimilation experimentations. The higher the assimilation frequency and the longer the assimilation time is, the more obvious the influence of data assimilation on the initial fields and forecast fields of the regional model is. But long assimilation time may increase the speed of synoptic systems and the overestimate rainfall, and so the suitable selection of frequency and time is crucial in numerical experimentations.