关键词: 伊犁河谷, 地基GPS, 降水, 大气可降水量

Abstract: 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.

Key words:  , Yili River Valley, ground-based GPS, precipitation, atmospheric precipitable water vapor