Abstract: The values of monthly mean water vapor content were computed using meteorological data from 3 radiosonde stations including Yining, Kuqa and Urumqi in the Tianshan Mountains and peripheral regions in Xinjiang, China during the period of 1976-2009, and a formula involving monthly mean water vapor content and surface vapor pressure was developed. The values of water vapor content at 44 meteorological stations in the Tianshan Mountains and peripheral regions during the period of 1961-2009 were computed and analyzed, the temporal and spatial distribution pattern of water vapor content and its relationship with precipitation was researched. Results are as follows: (1) There were three regions with high water vapor content in the Tianshan Mountains and peripheral regions, located in the valley plains in north piedmont of the Tianshan Mountains and Turpan Basin, and the water vapor content varied in a range of 12-21 mm. South Tianshan Mountains and Aksu, Korla and Hami were the regions with second high water vapor content, and the water vapor content varied in a range of 5-13 mm. The central and east parts of the Tianshan Mountains were the regions with low water vapor content, and the water vapor content varied in a range of 4-8 mm; (2) The variation curve of monthly water vapor content was unimodal, water vapor content was the highest in summer but lowest in winter, and the seasonal variation was significant. Water vapor content was increased during the period from February to July, its increase rate was the highest in March but the lowest in July, and the increase rates in these two months were 65.8% and 17.6% respectively. Water vapor content was decreased during the period from August to next January, its decrease rate was the highest in December but the lowest in August, and the decrease rates in these two months were 38.5% and 7.8% respectively. Monthly mean water vapor content in the Tianshan Mountains (7.83 mm) was lower than the average in whole Xinjiang (10.51 mm), in which the monthly mean and summer water vapor contents were the highest in the west Tianshan Mountains, they were 9.88 mm and 18.94 mm respectively; (3) The decadal variation of water vapor content was low during the period of 1961-2009, but water vapor content fluctuated significantly and was in an obvious increase trend after 1986; (4) There was no good correlation between water vapor content and precipitation.

Key words: water vapor content, surface vapor pressure, spatiotemporal distribution, precipitation, Tianshan Mountains