Comparison And Application Of Several Drought Monitoring Models Based On MODIS In The Northern Of Shaanxi, China

Drought is the water shortage which is caused by a regional imbalance in water supply and demand. Agricultural drought is the result of inadequate soil water supply led to normal growth and fertility of vegetation which has been held all over China, one of the major natural disasters. This article describes 5 kinds of remote sensing indexes based on the MODIS data:shortwave angle slope index (SASI), modify energy index (MEI), perpendicular drought index (PDI), surface water capacity index (SWCI) and vegetation supply water index (VSWI). In this Paper we have calculated the 5 indexes to get the spatial distribution of drought disasters in northern of Shaanxi province and then to use the soil moisture data which the weather station have measured to calculate the reliability and the precision. It gets the following conclusions. It's feasibly to use the MODIS data to monitoring soil moisture in the growth period of crop. The best depth of thermal inertia monitoring soil moisture is 20cm, and not useful for higher depth than 20cm.From the view of growth period, MEI, PDI and SWCI are better for the early, mid, and late period in the growth period. While in the whole period, SASI has the best relevance which is more than 0.6 in the indexes. From different regions in northern of Shaanxi province, SASI is compared for the sandy areas along the Great Wall in northern Shaanxi; SWCI has the best correlation with the Loess Plateau hilly region; Gully ecological forest zones has the most relevant to MEI. Through the analysis, the drought disaster has slowed down with the vegetation growing. The drought disaster is more serious in sandy areas along the Great Wall, mostly in severe drought, and light drought around Yulin and the Loess Plateau hilly region. In Gully ecological forest zones, a more adequate manner for the soil moisture, plant growth is in a good shape, there would have little effect with drought. There is good correlation between precipitation in the north region and the drought, but there is no apparent linear relationship between the temperature and the drought, while the south is on the contrary. The result may come from the impacts of geographical location and local topography.