Remote Sensing Retrieval Study Of Soil Moisture In Qmantage,Xinjiang Based On TVDI

With rich mineral resources and potential economical value,Qimantage area is located in the southeastern of Xinjiang Uygur Autonomous Region and,the area is about 33052km2. Based on MODIS data, this study utilized TVDI method to retrieve the soil moistures in the study area of growing season from 2004 to 2013. This study divided the study area into plains of waviness and lowland plains based on DEM data and compared the TVDI of two zones with TVDI of the study area seperately. Due to lack of field measurements, this study utilized the improved SEBS model to estimate the evapotranspiration,for validation of the TVDI results. Due to the rarely human activities in the study, we took the weather and NDVI as the main influence factors.The study reveals that:(1) The soil moisture in the study area is relatively stable, with no abnormal soil moisture in certain area. The minimum TVDI value(TVDI=0) was achieved in the Ayakekumu lake.In the middle of the study area and the Tulamuchang wetland, TVDI values are relatively small(0.2<TVDI<0.5), which means soil water contents were relatively high in these areas. In the northeast and west of the study area, TVDI values are relative high(TVDI>0.7), which means soil water contents are extremely low in these areas.(2) In plains and lowland plains,retrieved TVDI results of soil moisture are better.The effect of topographic relief, altitude and snow can resulted in lower soil moisture values.(3)maximum evapotranspiration is occurred in the Ayakekumu lake(ET>9mm), while the medium value is in the southeast of the study area(3mm<ET<7mm) and the minimum value is distributed in the northeast and west area(ET<2mm).The evapotranspiration has significant negative correlation with TVDI(R2>0.9),the higher the evapotranspiration values, the lower the TVDI values.(4) From 2004 to 2013, the temperature and the TVDI were in the same variation trend, but the precipitation and the TVDI were in the opposite variation trend. The NDVI values were relatively high(NDVI>0.5) in the the Tulamuchang wetland and east part of Ayakekumu lake, which indicated fine vegetation coverage in these areas.In the small part of southwest area, NDVI values are medium(0.2<NDVI<0.4), which indicated that the vegetation coverage in these areas is common.In the northeast and west of the study area, NDVI values are relatively low(0<NDVI<0.1),which indicated that the Vegetation cover there is extremely low. The NDVI values were minimum in Ayakekumu lake(NDVI<0),which indicated the area was covered by water. From 2004 to 2013, the NDVI and the TVDI were in the opposite variation trend,the higher the NDVI values,the lower the TVDI values.In general, although TVDI method has limitation in utilization due to limit condition of remote sensing, it has importance in soil moisture retrieval and drought monitoring in regional scale.