How can ENVI be used to monitor drought conditions in an area? Based on remote sensing. With extra points

Drought is one of the important factors affecting the development of agriculture in China, and the traditional drought monitoring is to monitor the degree and scope of drought with point data, which does not take into account the influence of other factors on drought. On the other hand, the application of remote sensing technology to monitor drought belongs to the monitoring on the surface, and fully utilizes the spectral, temporal, spatial and directional (multi-angle) of the surface of the features. Therefore, the conditional vegetation temperature index (VTCI), which is simultaneously correlated with the normalized vegetation index (NDVI) and the land surface temperature (LST), can be used for drought monitoring, especially for monitoring the relative degree of aridity of the whole region at a certain period of time in a given year, and can be used to study the spatial variability characteristics of the degree of aridity.