Effect Of Terrain On The Spatial Distribution Of Precipitation In The Tianshan Mountains

Based on the TRMM data, NCEP reanalysis data and observed data, the effect of terrain on the spatial distribution of precipitation in the Tianshan Mountains was analyzed using spatial analysis method. First, the relationship between underlying surface and water vapor distribution was analyzed. Then the influence of terrain on precipitation was discussed roughly. Last, the evaluation model for the precipitation in high resolution under complicated terrain was put forward. Based on this model, the spatial distribution of precipitation in Tianshan Mountains was estimated with 440m×440m resolution. The results were listed as follow:(1)The water vapor is closely related with surface feature in Tianshan Mountain. There are a lot of differences between precipitable water and actual rainfall in this region. The wet centers of precipitable water are located at low altitude region, such as Taklimakan desert, with low actual rainfall. On the other hand, the dry centers of precipitable water are located at high altitude region with high actual rainfall. The reason is that the precipitation conversion rate in the low altitude region is lower than the high altitude region. Also, the conversion rate in the east is higher than in the west, and that in the south is higher than in the north. The maximum of precipitation conversion rate with 360% appears in the Tumur Peak and Haerk Mountain in July.(2)The precipitation closely related with terrain. The maximum precipitation with 600 mm appears at about 2113 m and 3751 m elevation zones in the middle of Tianshan Mountain. The minimum precipitation appears at about 1266 m elevation zones. There is a positive correlation between precipitation and elevation under the 3751 m elevation zones.(3)The evaluation model for the precipitation in high resolution was established based on the relationship between precipitation and terrain. Their correlation coefficient in Kaiduhe river basin is 0.96. The percentage deviation is close to 0, and the root mean square error is 4.26. The results show that the model is good for the Tianshan Mountains. Also the simulated result is conformity with station observation data.(4) The model could estimate the spatial precipitation in Tianshan Mountains. It could reflect its relationship with moisture conditions, wind direction and topography conditions, windward slope and leeward slope. Based on water vapour and terrain, the spatial precipitation could be estimated. Result shows that this method is practicable and reliable for Tianshan Mountain area.(5)The variation of precipitation effected by terrain mainly distributes in the high altitude mountains, and is less than 300 mm. Most of variation concentrate between-100 and 100 mm, which changes significantly with seasons. There isn’t similar change characteristic with elevation. The reason maybe is that it is affected by the vapor, wind, topography, the condition of climbing the water vapor and formation of rain.Through the study in this paper, an evaluation model for the precipitation in high resolution, and maps of spatial distribution of precipitation in the Tainshan Mountains were obtained. This is the foundation of scientific management of water resources, as well as the sustainable development of agriculture and economy. It is help for the reasonable exploitation of water resource in the arid region of northwest China.