Studying of drought phenomena and vegetation trends over South Asia from 1990 to 2015 by using AVHRR and NASA's MERRA data

摘要

Drought is a severe climate fact that mainly results from low rainfall leading to serious threat of water shortages an ecological system of South Asia. Due to the current drought conditions and vegetation dynamics, the situation could further be intensified over South Asia. Thus, we study the drought impacts on vegetation dynamics over South Asia, aimed to find out the spatiotemporal differences in vegetation dynamics and seasons at which vegetation is determined by drought. Our approach is based on the using of advanced very high resolution radiometer (AVHRR) normalized difference vegetation index (NDVI) data and (NASA's MERRA) air temperature and rainfall data (1990-2015). Due to the low vegetation and dryness in South Asia, the NDVI is more helpful in describing the drought condition. From April to October, there were fast improvements in NDVI, VHI, and VCI. During September, the monthly VHI and VCI were stabilized and enhanced in October once more and in December again indicated a declining trend. The PCI, TCI, VCI, and VHI monthly values confirmed that in 2001, an extreme drought year, and continuous up to 2003, which lead the maximum drought in the South Asia regions. A considerably significantly correlation value in summer (JJA) and autumn (SON) seasons are showed between precipitation and NDVI. While the relationship between NVSWI and NDVI presented considerably high relationship in DJF, JJA, and SON, which specify an excellent indication for monitoring water stress. From 1990 to 2015, the difference of vegetation trend was obvious showed among various regions. The drought frequency was reducing trends from 1990 to 2015 over South Asia.