Up to now, all analysis of the distribution of water vapor over the Taklimakan desert area only depends on limited ground measurements and radio soundings setting mostly on the outer margin area. This paper establishes an approach to retrieve the water vapor over the desert at high temporal and spatial resolutions by the use of FY2C geostationary satellite split-window channels in cooperation with ground-based GPS water vapor measurement. Results show that the water vapor distribution over the Taklimakan desert is affected highly by topography and surface properties. The outer margin area has generally more water vapor than the inner area. Over the outer margin area, the western part has more water vapor than the eastern part, and the northern part has more than the southern part. The driest area lies to the south of Tazhong, east of Hotan River, and extended to the south boundary of the desert. Similar to elsewhere, water vapor over the desert area shows diurnal, monthly, seasonal and annual variations even at the driest inner area of the desert. In summer, the water vapor is transported from west to east over a long distance along the westerlies at a height between 700–400 hPa and with the average speed of 50 km h−1.

Diurnal variations in atmospheric water vapor are studied by analyzing 30-min averaged data of atmospheric precipitable water(PW) for 2004—2007 derived from Global Positioning System(GPS) observations at Peking university station(SA34).Comparing PW derived from GPS with that observed by radiosonde, the result shows that the root mean square error(RMSE) is less than 3 mm.On monthly mean, the curve of diurnal variations of PW is acquired,and composite diurnal variation of GPS PW,specific humidity, precipitation,temperature and wind vector are analyzed.The PW show a clear diurnal cycle with amplitude of about 3 mm in summer.A typical feature of the diurnal in Beijing is that the minimum value appears in the morning,and the maximum value appears in the midnight.There is some relations between the time of the maximum of PW and precipitation.The result of the wavelet analysis indicates that there is a 12-day cycle in most of the year.Precipitation occurs when the following two conditions are met:The instant PW is larger than the average PW of the past 12 days,and the other is the increment of PW in the last 16 hours is larger than the threshold.In summer,the most precipitation appears when the values of the minus value are high.Taking the above two conditions as the judging conditions,it could be prevented that the miscarriage of justice to precipitation when either the PW is high or the increment of the PW in 16-hour is larger than the threshold.