宁夏北部高温天气特征及预报分析

The high temperature weather features and analysis of forecast in the north of Ningxia

利用2000—2010年宁夏北部4个测站高温天气观测资料,结合同期NCEP/NCAR逐日再分析资料,对宁夏北部高温天气的高空环流特征、地面形势特征及物理量场特征进行了分析,总结归纳了宁夏北部高温天气的预报着眼点,为今后此类灾害性天气预报提供参考.结果表明,宁夏北部地区高温天气的主要高空影响系统为大陆高压、西太平洋副热带高压及蒙新暖脊;主要地面影响系统是位于90°～120°E、30°～50°N的热低压;物理量场上,700～850 hPa相对湿度低值中心都在宁夏北部,中心值基本都在10%～50%;散度场上,整层大气以下沉为主,有利于晴好天气维持及地面的增温;当对流层中低层温度露点差均大于15℃时,表明该地区上空的大气为干燥大气,在有利的大尺度环流条件下,易出现35℃以上的高温天气;探空图上,风向由低层到高层为顺时针旋转,表明有暖平流存在,暖平流控制宁夏北部值为80×10-5℃·s-1左右时,宁夏北部有高温天气,但副高控制下的高温天气温度平流不明显.

According to the high temperature weather observation data of 4 observation stations in the north of Ningxia during 2000-2010, combining with the corresponding period NCEP/NCAR daily reanalysis data, the high temperature weather features are analyzed. Some instructive information about high temperature forecast is obtained. Results show that upper air affection system of high temperature is mainly continental high pressure, the west Pacific subtropical high and the warm ridge from Mongolia to Xinjiang. The main ground influencing system is thermal low from 90°～120°E and 30°～50°N. Physical field shows that the low relative humidity center is in the north of Ningxia at 700-850 hPa which value is 10%-50%, divergence field shows that the whole layer of sinking atmosphere conducive to sunny weather, and warm the ground. When the difference of dew point temperature between middle and lower layer in troposphere were higher than 15 ℃, atmosphere over this region is dry, and in the favorable conditions of large-scale circulation, it is prone to be high temperatures above 35℃. On the sounding chart, wind direction, which rotates clockwise from lower to upper, indicates the existence of warm advection. If warm adveetion control is about 80×10^-5℃·s^-1, there is high temperature in northern Ningxia, but under the control of the subtropical high, temperature advection of high temperatures weather is not obvious.