GPS/PWV资料同化在强降水过程中的定量作用评估

基于WRF模式及其三维变分同化系统,分别采用江苏GPS观测网的大气可降水量资料及区域内探空和地面气象站资料,对2011年8月25日江苏苏南地区的一次区域性暴雨和2008年苏皖地区的一次局地特大暴雨过程进行了同化试验,用以比较分析GPS/PWV、探空和地面观测资料同化对强降水预报的定量作用。结果表明:探空和地面资料的同化通过对模式动力和热力场的影响,在强降水中心附近形成了强烈的辐合上升运动和热力不稳定条件,直接改进了强降水中心分布结构和强度特征,对数值模拟的成功与否起着决定性作用。而GPS/PWV在探空和地面资料同化的基础上,将使水汽条件得到增强且更有组织性,无论对降水中心强度还是位置都具有较为显著的改进作用。

Quantitative evaluation for GPS/PWV data assimilation in heavy precipitation events

Based on WRF model and the three-dimensional variation data assimilation system(WRFDA), using PWV data of Jiangsu GPS observation network, and regional radiosonde and surface data respectively, this paper carried out a series of assimilation experiments of two regional heavy rain events occurred in southern Jiangsu on August 25, 2011 and Anhui-Jiangsu on August 1,2008 in order to compare and analyze the quantitative effects of GPS/PWV, sounding and surface data assimilation on heavy precipitation forecast. The results showed that sounding and surface meteorological data assimilation affected the dynamic and thermal field, and formed the strong convergence with upward motion and the thermal instability near the rain center, then improved directly the distribution structure and the intention characteristics of heavy rain, so they played the decisive role in success or failure of numerical simulation. GPS/PWV assimilation enhanced and organized better the water vapor condition on the basis of sounding and surface data assimilation, and provided significant improvements in the intensity and the position of heavy rain center.