The Research On Time-spatial Distribution Of Precipitable Water In Taklimakan Desert

Hydrological cycle is one of the most important material circulations on the earth, and water vapor is the main atmospheric composition in the hydrologic cycle system.Taklimakan Desert is located in Tarim basin of Xinjiang province, the area has 330 thousand square kilometers.Such a large area of desert plays an important role in Land - Atmospheric interactions and hydrologic cycle. But because of severe condition, this area lack of water vapor observation for a long time. GPS has been emplaced in the hinterland of Taklimakan Desert since 2007, which has extremely vital significance for inverting and verifying the atmospheric precipitation data.The precipitable water(PW)of Taklimakan Desert was analyzed by GPS data , the radiosonde data and remote sensing of PW in near IR from MODIS,in order to understand space-time distribution characteristics of PW in this area.The main studying result of this paper included the following three aspects:Firstiy, the characteristics of daily variation of PW in the hinterland of Taklimakan Desert and the relationship between GPS PW and local precipitation were analyzed by use of the GPS data of Tazhong station from January to October in 2009. The results indicated that:(1) the characteristics of daily variation of PW in the hinterland of the Taklimakan Desert is obvious and presents a sine curve. The maximum appears in 8:00 am and 23:00 pm, and the values are 13.63 mm and 13.85 mm ,respectively. The minimum appears in 1:00am and 14:00pm, and the values are 12.91mm and 12.28mm ,respectively. PW in January is the least ,while the minimum values was 0.95mm at 13:00 on January 21 in winter. PW in July is the most,while the maximum values was 34.75mm at 7:00 on August 6 in summer .The maximum diurnal variation range of P is October.(2)Each precipitation process is consistent with the accumulation of water vapor ,and water vapor decreased quickly after the process. The relationship between the increment of GPS PW in 48h and precipitation is good. Before precipitation, PW rising sharply which portends precipitation will come. These results provides fundamental basis for short-term forecasting and nowcasting in precipitation.Secondly, using the radiosonde data and the observed meteorological data during 1989-2009, the change rule of PW in Taklimakan Desert was analyzed and an experiential vibration between PW and ground vapor pressure which was suitable for Taklimakan Desert was obtained.The calculating results of PW by using ground vapor pressure tally with the actual ones, which has a practical application prospect in the space-time distribution of water vapour in this area. The results indicated that: PW of the Taklimakan Desert show a significant decreasing trend since 2004.Thirdly , the analysis results of atmospheric precipitation indicates that: Taklimakan Desert is a relatively high value area of PW in northwest, and the value of PW is higher than the surrounding mountains; the areas of southwestern Taklimakan Desert where near to Qinghai-Tibet Plateau is a low value area of PW.