The study of the spatio-temporal changes of drought in the Mongolian Plateau in 40 years based on TVDI

This paper presents a new drought assessment method by modifying the NDVI-Ts space, which named NDVI-Ts general space. Based on this method, the general dry side and wet side equation were established for the period of 1981 and 2010 in the Mongolian Plateau. The results showed that: 1) the NDVI-Ts general space was more stable for monitoring drought than that for the single time Remote Sensing data; 2) TVDI was lower in the areas with high latitude, high vegetation cover, well-growing vegetation, which indicated higher soil moisture.3) The dry level area was the largest one, and the normal area was the second largest, the wet level area was the third, the extremely dry and extremely wet area was the least.4)The results showed that the fluctuated area mainly occurred in the normal level and the dry level, the extremely wet level, the wet level and extremely dry level basically remained unchanged. It may be explored that, the aridification became more serious in the 1981 – 2012, the area transformation mainly occurred between the normal level and dry level.