高山雷达VWP产品在暴雨预报中的应用研究——以丽江市为例

Application Research of Mountain Radar VWP Product in Forecast of Heavy Rains—Taking the City of Lijiang for Example

摘要: 选取丽江市四个气候站6年具有代表性的暴雨观测记录、CINRAD/CC雷达观测资料，对垂直风廓线(Vad Wind Profile，简称：VWP)在暴雨过程中的应用特征进行了统计分析。结果表明：VWP产品在暴雨过程降水前夕的主要特征有三个方面：1) 风向变化：在降水前夕风向随着高度的增加顺时针旋转即暖平流是其主要特征，还存在风的垂直切变、西南气流、风向随着高度增加逆时针旋转即冷平流等特征。2) 风速变化：风速随着高度的增大能促使降水的发生。3) 风向风速的同时变化：风随高度增加顺时针旋转且风速增大，在西南气流背景下，风速随高度增加；风向垂直方向上有切变，风速的增大等都有利于降水的发生。VWP产品在降水维持阶段的主要特征有：降水的维持与暖平流、冷平流、风的垂直切变有密切关系。VWP产品在降水减弱阶段除了与暖平流、西南气流，风切变的减弱有对应关系外，还有以下主要特征：一是在非冷平流系统中VWP产品的风向变为随着高度的增加逆时针旋转；二是VWP高层风向杆的突然下降；三是中层ND区域的出现，当VWP图像中层开始出现ND时，并且ND区域呈现上下扩展态势，降水一般在短期内停止。

Abstract: The typical rainstorm observation records of four climate stations and CINRAD/CC radar observations of 6 years at Lijiang are used to make a statistical analysis of the application characteristics of the Vertical Wind Profile (VWP) in the heavy rains process. Our results show that the VWP product on the eve of precipitation in the heavy rains process has three main characteristic as following: 1) The change of wind direction: on the eve of precipitation, the main characteristic is that the wind direction rotates clockwise with the increase of height, that is the warm advection, and there are also vertical shear of wind, southwest airflow, and counterclockwise rotation of wind direction with the increased height, that is the cold advection. 2) The change of the wind speed: the increased wind speed with height can promote the occurrence of precipitation. 3) Simultaneous change of wind direction and speed: the wind rotates clockwise and the wind speed increases with the increased height. Under the background of southwest airflow, the wind speed increases with height. In addition, the vertical shear of wind direction and the increase of wind speed are conducive to the occurrence of precipitation. There are main characteristics of VWP products in the stage of precipitation maintenance: the maintenance of precipitation is closely related to warm advection, cold advection and vertical shear of wind. In the weakening stage of precipitation, besides the corresponding relationship with the warm advection, southwest air flow and weakening of wind shear, VWP products have the following main characteristics: First, in the non cold advection system, the wind direction of VWP products turns counterclockwise with the increase of height. The second is the sudden drop of the wind rod at the high level of VWP. The third is the appearance of the ND region at the middle level. When ND begins to appear in the middle layer of VWP image, and the ND region shows a trend of expanding up and down, precipitation generally stops in a short period.