大气折射率结构参数夜间数据的降水预报属性

Characteristics of precipitation forecast for structure parameter of the refractive index at Night

LAS夜间出现低值时,常常(近90%)尾随降水过程。据统计,LAS夜间低值尾随的降水过程占全部降水过程的65%,而且包括了绝大多数大雨过程。因此,LAS夜间低值是很典型的、很重要的降水前兆。LAS夜间低值的量值对未来降水的降水量有明显的指示意义,当数值>7时,出现中、大雨的概率很小。而数值<7时,常常要下中到大雨。降雨多数(约65%)从低值出现后的10到34h中开始。有少数在更早或更晚的时段开始。文章揭示了降雨前低空存在一个湍流低值区,这个区的形成与降雨的形成过程,包括锋面逆温,水汽凝聚形成云下逆温等直接有关。

LAS shows low value at night and precipitation process often follow it（nearly90%）,which occupied 65% during the whole precipitation process.This phenomenon includes most large rain process,so low value of LAS at night is a good prelude to precipitation.The amount of low value has clear directive meaning to rain volume.When the value is larger than 7,it may not rain heavily.When the value is smaller than 7,there will be moderate rain or heavy rain.The rain usually starts from 10-34 hr after appearing the low value.Some of rain starts at early or later period.This paper reveals the fact that a low value area of torrent exists before it rains.The formation of the district and rain process are related to the low value,including frontal inversion,temperature inversion caused by vapor condensation.