多普勒雷达资料同化对江苏一次飑线过程的数值模拟

Numerical simulation of Doppler radar data assimilation on a squall line event in Jiangsu province

应用新一代中尺度预报模式WRF模式及其3DVar同化系统,针对江苏地区2009年6月14日飑线过程进行了多普勒雷达资料的同化试验研究,在对雷达资料进行严格质量控制的基础上,设计一系列尺度化因子优化调整及同化频率的敏感性试验。试验结果表明:同化后初始场得到不同程度改善,适当的尺度化因子设定,能够有效改进对模式初始场中700 h Pa风场和850 h Pa温度场以及组合反射率因子等要素的分析,进而改善短时降水预报和风暴的垂直结构配置;并且同化频率越高,对初始场的组合反射率因子分布与观测更为接近,短时降水预报越准确。

A new generation mesoscale WRF forecast model and its 3DVar assimilation system were used to conduct assimilation research of Doppler radar data on a squall line event on June 14,2009 in Jiangsu province. Based on strict quality control on the radar data,a series of sensitivity experiments about optimized adjustment of scale factors and assimilation frequency were designed and carried out. It is shown that the optimized adjustment of scale factors and assimilation frequencies can lead to the better performances of initial conditions. Specifically,the appropriate scale factors setting can effectively improve the distribution characteristics of 700 h Pa wind,850 h Pa temperature and composite reflectivity in initial conditions,then further improve the short-term precipitation forecast and vertical structure configuration of storm. Moreover,the higher assimilation frequency makes the distribution of composite reflectivity in initial conditions closer to the observation and makes short-term rainfall prediction more accurate.