Based on conventional ground observation data, TBB data of FY-2G satellite and NCEP/NCAR reanalysis data, the synoptic circulation pattern and mesoscale systems of the heavy rainstorm in Yili area of Xinjiang from 16 to 17 June 2016 were analyzed. And on this basis, the formation of the heavy rainstorm was analyzed in detail by using the output data of WRF model with high resolution. The results show that the main weather systems of the heavy rainstorm process were low trough in Central Asia, westerly jet in upper level, shear lines and convergence lines in lower layer. The multiple mesoscale cloud clusters sustained in Tianshan mountains area of northern Yili for a long time under the effect of terrain lifting, which caused strong rainfall continuously. The simulation result showed that the mesoscale convective cells moving continuously to the Tianshan mountains in northern Yili directly caused the heavy rainfall in Yili region, and the development of convective cells was closely related with low-level jets, low-level wind convergence and terrain. The dynamic convergence enhanced with increase of low-level jets, which triggered the release of CAPE (convective available potential energy), further led to the maintenance and rapid development of vertical motion together with terrain uplift, and caused the enhancement of convective system near convergence line in lower level, which were beneficial to the occurrence of heavy rainfall along Tianshan mountain of northern Yili.

Based on the NCEP/NCAR 0.25 ° × 0.25 ° reanalysis data, ERA-Interim 0.5°×0.5°reanalysis data, hourly and daily precipitation data, ground-based GPS precipitable water vapor data (PWV) from March 2016 to February 2017  at three stations in the Yili River Valley, temporal variation characteristics of PWV and its relationship with precipitation at three stations were analyzed. The evolution characteristics of PWV at different stations under different precipitation conditions and in different seasons were clarified. The results were as follows: (1) PWV had an obvious monthly variation, and it presented single-peak distribution at each station with the lowest value in January and the peak in July. The variation of PWV at Yining station was in consistent with the precipitation change from February to September (except July) but it was opposite from October to December. (2) The diurnal variation of PWV at each station presented double-peak distribution in spring and summer, the maximum  PWV appeared at 17:00 BST and 00:00 BST in spring, and it was 2-4 h later than that in summer. In autumn, the diurnal variation of PWV presented single peak distribution at Xinyuan station but it presented double peak distribution at  other two stations，while diurnal variation of PWV at three stations presented single-peak distribution in winter. As the altitude of the station increased, the variation of daily PWV increased gradually. (3) The maximum PWV was 0-3 h, 5 h, and 7-9 h ahead of precipitation, which was the highest  frequency. The occurrence time of precipitation in four seasons mainly was 0-3 h, 0-2 h and 5-7 h, 0-3 h and 7-9 h, and 0-1 h later than that of the maximum PWV, respectively. There were significant differences for PWV values in three stations under different precipitation conditions, and the higher the altitude, the less significant the difference was. (4) Humidification of PWV was related to the transport and inflow of water vapor in the lower troposphere before rainfall occurrence. During the precipitation period, the peak value of PWV and humidification time were different under different influence system and different water vapor transportation. The start time of precipitation had a good correspondence with peak  value of PWV. During the precipitation period, there was  a significant vertical transport of water vapor over the rainstorm area, which resulted in a gathering area of ice water formed in clouds in the middle and upper troposphere, PWV transition and short-term heavy rainfall at the station.

This paper dynamically discussed the development mechanisms of local rainstorm triggered by gravity waves，and proposed a feasible method，which was verified by a case study，to forecast the propagations of gravity waves． The results showed that:( 1) the propagation of gravity waves strictly consistent with the potential temperature ridge，and by analyzing the isentrope，the forecasting of the generation and evolution of gravity waves would be more effective; ( 2) the waves could travel from higher potential temperature to lower side，or propagate in reverse orientation; ( 3) there were corresponding relations between the propagation path of gravity waves and the surface convergence line． Though the waves propagated along with the convergence line，it did not generate the gravity waves;
( 4) in a case of rainstorm on 9th August 2011 in Shijiazhuang，the gust front generated the gravity waves as a triggering mechanism， and brought about strong rainfall in the west urban．