State Key Laboratory of Grassland Agro-ecosystems, Lanzhou University, Lanzhou, 730020, People's Republic of China.
Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs, Lanzhou University, Lanzhou, 730020, People's Republic of China.
Environ Sci Pollut Res Int. 2021 May;28(17):21085-21100. doi: 10.1007/s11356-020-12124-w. Epub 2021 Jan 6.
Due to various land cover changes, vegetation dynamics, and climate, drought is the most complex climate-related disaster problem in Tibet and Xinjiang, China. The purpose of the present study is to analyze the performance of the AVHRR Normalized Vegetation Index (NDVI) and the temporal and spatial differences of seasonal vegetation dynamics by correlating the results with rainfall and temperature data of NASA's MERRA to examine the vegetation dynamics and droughts in Tibet and the Xinjiang Province of China. Our method is based on the use of AVHRR NDVI data and NASA MERRA temperature and precipitation during 1983-2016. Due to the dryness and low vegetation, NDVI is more useful to describe the drought conditions in Tibet and Xinjiang of 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, again improve in October, and then confirm downward trend in December. The NDVI, TCI, VHI, NVSWI, NAP, VCI, and TVDI monthly values indicate that Tibet and Xinjiang province of China suffered from severe drought in 2006, 2008, and 2012 which were the most drought years. For monitoring drought in Tibet and Xinjiang province of China, the NDVI, TVDI, NAP, VCI, and NVSWI values were selected as a tool for reporting drought events during different growing seasons. Seasonal values of TVDI, NDVI, NAP, NVSWI, and VCI confirmed that Tibet and Xinjiang province of China suffered from severe drought in 2006, 2008, and 2012 and led the durations of severe drought. The correlation between NDVI, TCI, VHI, NAP, TVDI, and VCI showed a significantly positive correlation, while the significantly negative correlation between NVSWI and NDVI showed a good indication for the assessment of drought, especially for the agricultural regions of Tibet and Xinjiang province of China. This shows that the positive sign to support NAP, NVSWI, and TVDI is good monitoring of the drought indexes in Tibet and the Xinjiang province of China.
由于各种土地覆盖变化、植被动态和气候因素，干旱是中国西藏和新疆最复杂的气候相关灾害问题。本研究的目的是通过将结果与 NASA 的 MERRA 的降水和温度数据相关联，分析 AVHRR 归一化植被指数（NDVI）的性能以及季节植被动态的时空差异，以研究中国西藏和新疆的植被动态和干旱情况。我们的方法基于使用 AVHRR NDVI 数据和 NASA MERRA 在 1983-2016 年期间的温度和降水数据。由于干燥和低植被，NDVI 更有助于描述中国西藏和新疆的干旱情况。从 4 月到 10 月，NDVI、TCI、VHI、NVSWI、VCI、TVDI 和 NAP 迅速增加。而在 9 月，NDVI、TCI、VHI、NVSWI、NAP、TVDI 和 VCI 每月都保持稳定，然后在 10 月再次提高，然后在 12 月确认下降趋势。NDVI、TCI、VHI、NVSWI、NAP、VCI 和 TVDI 每月值表明，中国西藏和新疆地区在 2006 年、2008 年和 2012 年遭受了严重干旱，这是最干旱的几年。为了监测中国西藏和新疆地区的干旱情况，选择 NDVI、TVDI、NAP、VCI 和 NVSWI 值作为报告不同生长季节干旱事件的工具。TVDI、NDVI、NAP、NVSWI 和 VCI 的季节值证实，中国西藏和新疆地区在 2006 年、2008 年和 2012 年遭受了严重干旱，并导致严重干旱持续时间延长。NDVI、TCI、VHI、NAP、TVDI 和 VCI 之间的相关性呈显著正相关，而 NVSWI 和 NDVI 之间的显著负相关表明对干旱的评估，特别是对中国西藏和新疆地区的农业地区。这表明，支持 NAP、NVSWI 和 TVDI 的正号是对中国西藏和新疆干旱指数的良好监测。
