Features of Precipitable Water Vapor by GPS in Different Cloudform Precipitation——Analyses on Some Typical Cases in North China

Based on the precipitable water vapor received from ground-based GPS and surface meteorological data in Shijiazhuang,Qinhuangdao and Zhangjiakou city in April~October 2005-2006,the relation between precipitable water vapor and real precipitation are studied.With the analysis of precipitable water vapor in convective precipitation produced in the cumuli form,steady precipitation in the stratiformis cloud,and the heavy rain in the laminose and mixed stratiformis cloud,some valuable conclusions are put forward in this paper,the results are as follows: It is a necessary condition that high precipitable water vapor exist in the air.Precipitable water vapor change according to wave shape and phases character,there is a good relationship between change extent,maximum level,duration and weather system,precipitation kinds and etc.The oppearing time of maximum value between rainfall intansity and precipitable water vapor is uncertain coincidence,but it is known that severe rainfall usually begin at the period of high value of precipitable water vapor,and high value of precipitable probability is parallelism with the latter.In addition,there is different characteristics in the above three different precipitable kinds,and these results provide a reference for the short range forecasting and now-casting.