LAUSR

Due to the present drought events and dynamics of vegetation, the circumstances in mainland China could become even more serious. Therefore, we study the impact of drought on vegetation trends in mainland China, with the aim of discovering the temporal and spatial differences in vegetation dynamics caused by seasonal drought. Our method is based on the use of data from the AVHRR Normalized Difference Vegetation Index (NDVI) from 1983 to 2016 and temperature and precipitation data from Modern Era Retrospective Analysis for Research and Applications (NASA’s MERRA). Due to the sparse vegetation and low drought, NDVI is the most useful for describing drought conditions in mainland China. The NDVI, TCI, VHI, NVSWI, VCI, TVDI, and NAP from April to October increased rapidly, while the NDVI, TCI, VHI, NVSWI, NAP, TVDI, and VCI are stable every month in September, improve again in October, and then show in December a downward trend. The NDVI, TCI, VHI, NVSWI, NAP, TVDI, and VCI monthly values indicate that mainland China suffered from severe drought in 1984 and 1993, which lasted until 2007, which were the most drought years. For monitoring drought in mainland China, the NDVI, TVDI, NAP, VCI, and NVSWI values were selected as a tool for reporting drought events during different growing seasons. The seasonal values of TVDI, NDVI, NAP, NVSWI, and VCI confirmed that mainland China suffered from severe drought in 1984, 1993, and 2007 and led the durations of severe drought. Spatial correlation is generated between NDVI, TCI, VHI, NVSWI, NAP, TVDI, and VCI. The correlation between NDVI, TCI, VHI, NAP, and VCI showed a significantly positive correlation while significantly negative correlation between NVSWI and TVDI, TVDI and VHI, which showed a good indication for the assessment of drought, especially for the agricultural regions of mainland China. This shows that the positive sign to support NAP, NVSWI, and TVDI is a good monitoring of the drought indices. During the summer, it appears that compared to the southeastern part of mainland China, drought is more likely to occur in the northwestern areas. There is no doubt that these drought indices are comprehensive indicators of monitoring drought events in mainland China.