Study On The Remote Sensing Invesion Of Snow Depth Based On Digital Terrian In Tianshan Mountains

Snow monitoring is a hot topic in recent years. With the development of remote sensing technology, it becomes more common in the snow field. Because of high time and space resolution, strong penetrability and getting easily, the passive microwave radiation data becomes the main data for snow depth research, especially for the mountain regions with complex terrain, little stations and short of data. In order to understand the distribution characteristic of snow depth in Tianshan Mountains and reveal its change law, we developed a new algorithm of snow depth for Tianshan Mountains based on the SSM/I data.Based on the observed snow depth in meteorological stations and the radiation brightness temperature data of passive microwave(November 1, 1994 to March 31, 2013), snow depth in Tianshan Mountains was computed. According to the characteristics of microwave radiation in different underlying surfaces, the underlying surface was divided into four classes: cultivated land, grassland, forest land and bare land based on the brightness temperature. The inversion algorithm was set up. Then the daily snow depth and maximum snow depth from 1994 to 2013 were calculated. The map of annual maximum snow depth and monthly maximum snow depth could be obtained. The spatial and temporal law of Tianshan Mountains’ snow depth was analyzed. The spatial heterogeneity of snow depth in Tianshan Mountains with elevation and relief amplitude was discussed. The main conclusions were listed as follows:(1)The accuracy of the model shows that the model error is no more than 6 cm, and the minimum error with 3.71 cm appears in the grassland. The maximum with 7.25 cm appears in the forest. The total recognition accuracy arrived at 84%, which has higher accuracy in Tianshan Mountains than the standard algorithm. The snow depth in the high snow depth would be underestimated.(2)The snow depth in Tianshan Mountains decreases during 1994 to 2013. The snow depth in Yili valley and Bortala, located in the middle and north of Tianshan, is much higher than other areas. The value of snow depth in the eastern and southwestern Tianshan is very small, particularly in the region of Hami and Kashi. The snow depth exceeds 50 cm around the Bogda Peak, however, the lowest snow depth with 10 cm appears in the Hami.(3)The analysis of snow depth shows that the change of snow depth in snow season is like a peak. The maximum snow depth is only 24 cm in November. The high frequency snowfall appears in December with 50 cm snow depth. In January, the maximum snow depth could reach 51 cm, in which snow depth arrives at the largest. Then the snow depth begins to decrease in February and March. Its maximum could reach 46 cm and 44 cm, especially.(4) There is positive correlation between snow depth and elevation in the elevation area of less than 4,500 meters. This is because strong wind and complex terrain go against accumulation of snow in the high altitude area. In the other hand, water is very rich in the windward slope, which is conducive to accumulation of snow and leads to the snow depth in the windward larger than that in the leeward slope.(5)Relief amplitude is negative correlated with snow depth. That is to say, snow depth decreases with relief amplitude. The distribution of snow depth closely related to terrain condition. In the small rugged area with plain and hilly terrain, the value of snow depth is very large. Snow depth in the large rugged area is much lower than that in small rugged area with complex terrain and diversity of slope.