大同市一次暴雪天气过程多普勒雷达速度特征

Velocity characteristics of Doppler radar from a heavy snow process in Datong,Shanxi province

利用高空、地面环流形势图、欧洲数值预报产品和大同地区C波段单多普勒雷达产品中的反射率因子、径向速度和VWP产品,对2009年11月9—10日发生在大同地区的暴雪天气过程进行综合分析。结果表明:地面回流和高低空急流是产生强降雪的主要原因;较大降雪回波与连续性降雨回波存在相同特点。利用大面积降水的多普勒雷达PPI径向速度零线的朝向、正负速度面积和径向速度值的大小定性判断辐合辐散图像特征与根据零速度线的弯曲程度、一定距离圈上零速度点与雷达中心连线夹角计算出的辐散值相比较,表明两种方法具有较好的一致性,可以在实际工作中对辐合、辐散快速判断。由重新处理的雷达原始资料求得每30 min的雷达风廓线资料,可以清楚地展示强降雪风场的垂直结构及其变化,直观地反映降水过程中的风场变化特征。

Based on the circulation patterns at the upper air and surface,numerical weather prediction products from the ECMWF model,Doppler radar products from C-band such as reflectivity factor,radial velocity and VWP products in Datong,the heavy snow process on November 9-10,2009 was analyzed.The results indicate that the surface return current and jets in upper and lower levels are the main reasons causing the heavy snow.The echoes characteristics of a heavy snow and a continuous rainfall are similar.The convergence and divergence can be estimated using a direction of the zero line,the areas of the positive and negative velocity and radial velocity value.They can also be calculated using the curving extent of zero velocity line and the included angle between zero velocity point in the stationary range and radar center line.The results calculated using the two methods are in good consistency.Both could be used to judge convergence and divergence quickly at work.Doppler radar wind profile data per 30 minutes could be obtained by rehandling primeval data,and it can display clearly the vertical structure of wind field of the heavy snow and its changes and it can reflect intuitively the wind field features.