一次阵风锋的观测实例和分析

针对2007年3月2日-4日出现在黄土高原干旱地区的一次大范围较强降雨过程，利用常规气象观测资料和多普勒雷达监测资料进行了分析，发现：这次降雨为积层混合云降水，在强度PPI上具有回波范围大，分布较均匀、连续，边缘不规则等连续性降雨回波特征；VIL的变化与降水发生有明显的正相关，对降水过程的发生有一定的指示意义；多普勒径向速度的PPI图像中各个圈层正、负速度值的大小和同一风速值所对应的面积大小可以判断各个高度层风向、风速的辐合辐散；由零速度线的走向可以定性判断辐合辐散与冷暖平流，进而推断降水的生消。通过对此次降水个例的分析，探讨了春季强降雨过程的雷达图像特征，为干旱区春季大面积降水预报积累经验、提供一定的参考依据。

Analysis of New Generation Weather Radar Image Characteristics for Heavy Precipitation of Arid Area in the Spring

According to a heavy and large- scale precipitation which occurred in arid areas of the Loess Plateau in March 2 to 3, 2007, the routine weather observation data and Doppler radar data were analyzed. The result show： this precipitation was from cumulostratus. The radar echo had many characteristics of continuous precipitation such as large scale, symmetrical distribution, continuous and irregular edge and so on. Changes of VIL and precipitation appearing had an obvious positive correlation. It has some hint for occurrence of precipita- tion. The positive and negative values of Doppler radial velocity in each of the PPI image circle and the area with same wind speed could determine wind direction and wind speed of convergence divergence of each level. By the zero - speed line orientation can be characterized to determine the convergence and divergence and cold and warm advection, and inferred dissipation of precipitation.