副高边缘暴雨过程中的GPS可降水量和假相当位温分布特征

利用2010年8月石家庄地基GPS反演的可降水量、地面加密自动站和常规天气资料,对由副高进退引起的河北省中南部一次强降水天气过程中GPS可降水量和地面假相当位温的演变趋势进行了详细分析.结果表明:1)此次暴雨过程是由副高边缘暖湿气流与切变线共同作用造成的,强降水区主要出现在500 hPa的584～588 dagpm线、700～850 hPa切变线之间;2)降水出现时GPS可降水量基本对应于高值阶段,强降水出现时可降水量位于峰值前后;降水出现时GPS可降水量偏离系数为正值,而强降水一般出现在偏离系数超过1时;3)对同一测站而言,GPS可降水量越大对应的实际降水越强.当测站不同时,GPS可降水量高并不一定代表更强的降水,这与测站的地理位置和海拔高度有关.4)降水出现前热力和水汽条件配置好,能量不断积累,假相当位温逐渐升至极大值.随着降水出现与能量的释放,假相当位温回落到谷值阶段,此谷值越低、持续时间越长,对应的降水也越强.

Characteristics of GPS-retrieved precipitable water vapor and ground pseudo-equivalent temperature during a heavy rain of western pacific subtropical high

Based on precipitable water vapor retrieved from ground-based GPS,data of ground automatic meteorological stations and conventional weather data,the evolution tendency of precipitable water vapor and ground pseudo-equivalent temperature during a heavy rain in south central Hebei province is studied.The results show that the heavy rainfall are caused by warm-wet flowing and shear line at the edge of subtropical high,and the precipitation area is between 584 to 588 dagpm lines in 500 hPa,between shear line in 700 to 850 hPa.Rainfall usually occurs when the GPS-retrieved precipitable water vapor is higher than the average value,especially near its maximum value,and the heavy rain period is corresponding to the maximum value stage of precipitable water vapor.Rainfall occurred more often when the deviation coefficient of GPS-retrieved precipitable water vapor is positive,heavy rainfall generally happens while deviation coefficient is higher than 1.For the same station,when GPS-retrieved precipitable water vapor is high,the real precipitation is strong.While for the different stations,the high precipitation is not necessarily represent strong real rainfall,for it is corresponding to the station location and altitude.High-energy accumulation is a necessary condition of rainfall.The rainfall of subtropical high usually occurs in the rapid decline phase of pseudo-equivalent temperature or its valley areas.The precipitation will be stronger when pseudo-equivalent temperature is at high peak,in sharp movement and with long duration of high value.