用雷达反演资料诊断江苏地区一次暴雨过程

对2010年7月12日发生在江苏中部地区一次暴雨天气过程产生的原因、多普勒雷达图像产品特征及由雷达数据反演的物理量场进行了诊断分析和定量评估,得出如下结论:雷达径向速度图像特征变化反映了风场辐合辐散特征的变化,有助于了解雨势增减情况。多普勒雷达径向速度提取的散度数据与NCEP散度数据整体趋势上是一致的,但辐合辐散中心区位置及强度存在差别,雷达反演散度强度较NCEP大4~5倍,天气过程变化期间两者散度在垂直高度场的配置调整均能反映降水动力场变化;400hPa及以下高度反演的平均散度更可信;对于雨强小于等于16mm/h的降水天气过程效果更好。由雷达基数据定量计算得到的平均散度特征和垂直速度随时间和高度的变化,能较好的反映出强降水过程的动力学特性;雷电频次与强降水出现时次有一定相关性,约有1~2h提前量,雷电发生随时间演变与雷达回波强度时空分布较为吻合,云底动能施力参量一定程度可以描述闪电增长情况,较降雨量约有40min左右的提前量,有一定预警能力。

Diagnostic analysis on a rainstorm of Jiangsu province by radar inversed data

The reasons, radar image products features and radar inversed physical quantity of a rainstorm in the central Jiangsu on 12 July, 2010 are diagnostically analyzed and quantitatively estimated. Results show that the wind field divergence feature reflected by the radar radial velocity helps understand the rain tendency. The divergence data extracted from the Doppler radar radial velocity and from NCEP tended to be consistent, but differences existed in position and intensity between convergence and divergence. The radar inversion divergence intensity is 4-5 times stronger than the NCEP one. Both of the two divergences during the adjustment of vertical height field configuration can reflect precipitation dynamic field change of the heavy rainstorm. The average divergence inversed below 400 hPa is more reliable, especially for the precipitation process whose rainfall rate was lower than 16 mm/h. The average divergence and vertical velocity characteristics calculated quantitatively by the radar base data turned to change with time and height, which reflected the dynamics characteristics of strong rainfall process;the frequent lightning appeared 1-2h ahead of the rainstorm occurrence, and the evolution of lightning with time was consistent with the temporal and spatial distribution of radar echo intensity, so that it is feasible to describe the lightning growth by E_kin, and there were 40 mins approximately before rainfall, which helped forecast rainfall.