摘要
对短时强降水主观临近预报的主要思路和方法进行综述。(1)短时强降水(flash heavy rain)是指1 h雨量在20 mm或3 h雨量在50 mm以上的降水事件。短时强降水事件的识别主要由雨强和降水持续时间两个要素确定。(2)雨强临近估计的主要根据是天气雷达反射率因子和雨强之间的经验关系,即Z-R关系。对流性雨强的估计,最简单易行的方法是将对流性降水分为大陆强对流型和热带海洋型两种类型,分别采用不同的Z-R关系。雨强估计的主要误差来源包括不适当的Z-R关系、地形对雷达波束阻挡、冰雹"污染"、强降水和冰雹对雷达波束的衰减、硬件定标偏差、被大雨淋湿的天线罩导致的衰减等。(3)判断是否出现强降水的另一要素是降水的持续时间。沿着回波移动方向高降水率的区域尺度越大,降水系统移动越慢,则持续时间越长。对于导致强降水的β中尺度对流系统,其雷达回波的移动矢量是平流矢量和传播矢量的合成。如果平均风方向(平流方向)与回波传播方向交角大于90°,称为后向传播,此时回波移速小于平均风速,移动较慢,易导致强降水。在有利于强降水的环境条件下,含有中气旋或更大尺度涡旋的β中尺度对流系统会明显增大强降水的可能。
This paper overview the main idea and methodology used in subjective nowcast of flash heavy rain. Flash heavy rain refers to the rainfall events with one-hour accumulated precipitation over 20 mm or three-hour accumulated precipitation over 50 mm. The identification of a flash heavy rain event relies on two factol~： the rainfall rate and the duration of rainfall. The rainfall estimation is based on the empirical relation between radar reflectivity factor （Z） and rainfall intensity （R）, i.e., Z-R relationship. The simplest approach to estimate precipitation is to divide lhe convections into two categories： ＂＇continental severe convection＂ and ＂tropical maritime convection＂, and then apply different Z-R relationship for each type. The primary errors in the precipitation estimates are resulted from improper Z-R relationship, terrain block- age, hail ＂pollution＂. attenuation by heavy rain and hail, inaccurate radar calibration, attenuation by wetted radome, etc. Another important factor in flash heavy rain nowcast is to estimate the duration of heavy rain. Both the larger of the size of heavy rain area is along the echo＇ s moving direction and the slower the echo moves, the longer the severe precipitation lasts. The backward propagation type MCS is more likely to lead to flash heavy rain for its relatively slow moving speed. In the case of strong vertical wind shear, the M^CS embedded ira mesocyclones or wider range vortices have a higher probability to produce flash heavy rain.
出处
《暴雨灾害》
2013年第3期202-209,共8页
Torrential Rain and Disasters
基金
国家973项目"突发性强对流天气演变机理和监测预报技术研究"(2013CB430100)
国家自然科学基金项目(41175043)
关键词
短时强降水
临近预报
大陆强对流降水型
热带海洋降水型
后向传播
中气旋
flash heavy rain
nowcast
continental convection type
marine tropical convection type
backward propagation
mesocyclone
