Retrieving Soil Moisture of Shiyang River Basin by ATI and TVI Based on EOS/MODIS Data

Abstract

This paper intends to examine spatial distribution of soil moisture in Shiyang River basin in eastern Hexi corridor,an important arid ecosystem in Northwest China.The MODIS data MOD11A2,MOD13A1 and MCD43A3 were used to compute such parameters as NDVI,ATI and TVI required for the study.An applicable approach from ATI and TVI has been proposed to estimate the soil moisture in the basin,using NDVI as a threshold for each pixel.The approach was validated with the field data.The distribution pattern of the soil moisture in Shiyang River basin was further analyzed using DEM data.The results show that the compound ATI and TVI models can effectively improve retrieval accuracy and remedy the shortage of one-sided method.The results were acceptable through a comparison with the field data.The study reveals that in Shiyang River basin,the soil moisture is degressive from the upstream area to downstream area,and it is obviously lower in the sloping land of foothills,the edge of oasis and desert area.Relatively,the soil moisture has observably changed in the upstream and downstream areas and marginal areas of oasis.In Shiyang River basin,the soil moisture distribution shows significant differentiation with the change of elevation,slope and other terrain factors.In Shiyang River basin,the drought is mainly distributed in farmland and grassland,and the drought extent of farmland is in different degrees of seriousness in different landuse types.