雷达风场提取螺旋度和散度信息方法及应用研究

首先应用Sirmans的模拟多普勒速度仿真信号技术，分析平均风场、平均散度和本项目拟研究的螺旋度的计算误差。当无降水回波时，应用晴空回波速度资料通过VAD技术反演平均风场信息和平均散度。计算地面相对螺旋度及其沿垂直方向的积分形式，以定量获取低层大气冷暖平流信息。计算标准化地面相对螺旋度及其沿垂直方向的积分形式，以评估风垂直切变的作用。在晴空回波区以外的探测范围内出现降水回波时，另外再计算风暴相对螺旋度及其积分形式。在晴空回波范围内出现降水回波时，除计算上述各种螺旋度外，考虑到雨滴下落速度的影响，应用EVAD技术提取大气平均散度信息。应用所提取的平均散度和各种螺旋度信息，结合多普勒天气雷达其他产品，预测风暴发展动态。通过本项目的研究，可以进一步挖掘多普勒天气雷达的探测潜力，更加清楚了解风暴发生演变过程，提高风暴降水的预警预报准确率，发挥最大效益。

First a technique of computer-simulated Doppler signal from Sirmeans (1975) is applied to analyze mean wind fields, mean divergence fields and calculated errors of the helicity of this project. When it is fair weather, the data of clear air Doppler velocity is used to retrieve mean wind and mean divergence fields by using VAD method. With the calculated surface relative helicity and its vertical layers integration, the cold or warm advection of low level atmosphere is obtained quantitativly. The influence of vertical wind shear is evaluated by calculation of normalized surface relative helicity and its vertical layers integration. If the precipitation echoes appear outside the observation ranges of clear air echoes Doppler velocity scan mode, it is necessary to calculate storm relative helicity and its vertical layers integration. If the precipitation echoes appear within the observation ranges of clear air echoes Doppler velocity scan mode, in addition to the calculation of the above mentioned helicities, considering the fall speed of raindrops, the EVAD technique is applied to extract the mean divergence of atmosphere. Via the extracted mean divergence and various helicities values, and in combination with other products of Doppler weather radar, the convective storm growth can be predicted. This study can explore the detection potential of Doppler weather radar and better understand the process of the growth, maintaining and decay of storms. It will improve the accuracy of forecast of hazards compared with the previous methods and further enhance the warning capability to maximize the benefits.