春季一次暴雪过程的多普勒雷达动力学诊断

利用太原C波段多普勒天气雷达基数据资料和自动雨量站资料，对2006年4月11日发生在山西省的一次区域性暴雪过程进行了分析。应用改进的EVAD技术，定量计算垂直高度层的平均散度和平均垂直速度，并分析平均散度和平均垂直速度随时间和高度的变化以及与降雪的对应关系。结果表明：2．5km以下始终维持一个较强的上升气流，是强降雪维持的基本动力条件；整层出现辐合上升运动，且强上升速度中心的高度随时间的演变逐渐下降，同时中高层出现强辐散下沉气流与之配合时，未来2小时将出现强降雪；降雪的强度与雷达探测范围内各高度层的辐舍、辐散有着密切的关系，且辐合、辐散的增强与减弱时间早于降雪强度的增大和减小时间，这对预报降雪的生消、雪强的增大与减小提供了一定的理论依据。

Dynamical Diagnosis of the Spring Snowstorm Process Based on Doppler Weather Radar

By using the data of C-Wave Band Doppler weather radar and the precipitation data from AWS in Taiyuan, a regional snowstorm event occurring in Shanxi on April 11, 2006 was analyzed. The average divergence and vertical velocity of the vertical height layers were calculated quantitatively with the improved technology of EVAD. Their changes in time and space and the corresponding relationship with this snowstorm were further investigated. The results indicate that the strong updraft always keeping less than 2.5km is the basic dynamical main taining mechanism of heavy snowstorms; if anabatic movement appears in whole lower layer and the height of the strong updraft center is lower and lower along with time accompanying with strong downdraft in middle-high layers, then heavy snowstorm will appear in 2 hours later there. The intensity of snow is closely related to the divergence and convergence in each height layer within the radar's coverage, and the intensification or decrease of the divergence and convergence appears ahead of that of the snow intensity. These results provide some theoretic basis for forecasting the occurrence and disappearance of snowfall and the development of snow intensity.