Study on monitoring drought in China with MODIS product

In this paper,the 16 days' composite Normalized Difference Vegetation Index(NDVI) and 8 days' composite land surface temperature product in China are used to establish NDVI-Ts,NDVI-ΔT and NDVI-ATI space.From these spaces,temperature vegetation dryness index(TVDI),difference temperature vegetation dryness index(DTVDI) and apparent thermal inertia vegetation dryness index(AVDI) are suggested respectively to evaluate drought in every three agricultural climatic regions in China.The measured topsoil moisture is used to compare with TVDI,DTVDI and AVDI.From NDVI-ΔT spaces,we found that the wet edges are all parallel to the abscissa and the wet soil has the same power to hold back temperature change with the vegetation non-water stress.In NDVI-ATI space,ATI increases with the increase of NDVI.After we compare the measured topsoil moisture with TVDI,DTVDI and AVDI,the result shows that TVDI has a more significant linear correlation with soil moisture than the other two,and TVDI is the most promising method in monitoring drought for large region; DTVDI still has the potential on monitoring drought while AVDI is not competent for monitoring drought.