In this research study,ground-based GPS Perceptible Water Vapor(PWV) data,which was based on routine observational data,satellite images,and NECP 1°×1° reanalysis data,were used to examine a large-scale severe precipitation process which had occurred in Chengdu from September 23rd to 26th of 2008.It was found that the storm had been caused by a combination of cold air from the north,warm moist air from the Bay of Bengal,and the high and low torrents from a "Hagupit" typhoon.Prior to the rainstorm,the water vapor of the middle and lower troposphere was observed to be sufficient,and the atmospheric stratification was extremely unstable.In addition,vertical wind shear had been obvious.During the rainstorm period,the majority of the water vapor was concentrated in the 900 to 500 hPa layers,and was mainly composed of the warm wet air brought in by the southwest monsoons and cold air originating from a "Hagupit" typhoon in the South China Sea.The results of this study's comparison of the satellite cloud data indicated that the heavy ground precipitation center was not only related to the entire layer of the water vapor transmission center,but also had a close relationship with the water vapor transmission intensity.It was observed that the larger the water vapor flux was,the greater the precipitation would be.Meanwhile,the GPS-PWV was also found to be sensitive to the strength of the water vapor transmission.For example,when the water vapor had reached a baseline,the probability of precipitation was greater.Also,the longer the water vapor amount had been maintained at a high-value stage,the longer the duration of the precipitation and the stronger the intensity would be.It was also determined that the maximum amount of precipitation was not necessarily consistent with the time that the peak precipitation had been reached.However,it was observed that the heaviest rainfall had usually occurred when the precipitation was in the fastest rising stage.The results of this study indicated that before and after the rainstorm event,the precipitation could be divided into increasing and decreasing stages,respectively.Therefore,the high temporal resolution observations of the ground-based GPS were able obtain the rapidly changing information of the water vapor,along with certain indications of the occurrence time and strength of the rainstorm event.This type of information could potentially play an important role in the real-time monitoring of the occurrences and development of rainstorm events in the future,and also provide important references for the future construction of ground-based GPS stations in the Chengdu area.In this study,when the findings were combined with the results of the mesoscale numerical simulation WRF,it was found that the examined rainstorm event was more dependent on various dynamical and thermodynamic conditions than on the values of the PWV.Furthermore,the strength of the moisture convergence had played a crucial role in the examined rainstorm event.