Abstract
Abstract. Drought is an extremely complex natural disaster phenomenon. Sustained drought will lead to the aggravation of water shortage, food production reduction, land desertification and ecological crisis, which will have a great impact on social and economic development, industrial and agricultural production and ecological environment. In recent years, human activities have intensified, the global climate has been warming, and the frequency and intensity of extreme events such as drought have been continuously strengthened, which has been widely concerned by scholars at home and abroad. The Beijing-Tianjin-Hebei region, as the political and cultural center of China, is seriously affected by the drought, which has a certain impact on the social economy of the region. Therefore, it is of great practical significance to carry out remote sensing drought monitoring and understand the temporal and spatial characteristics of drought. Based on MOD13A2 and MOD11A2 in MODIS products, this paper constructed the NDVI-Ts feature space to obtain the Temperature Vegetation Dryness Index (TVDI) in Beijing-Tianjin-Hebei region, and analyzed the spatial and temporal variation characteristics of drought in Beijing-Tianjin-Hebei region from 2001 to 2014 with TVDI as the drought index. The results showed that: (1) the NDVI-Ts feature space in the Beijing-Tianjin-Hebei region showed that when the value of NDVI rose from 0 to 1, the maximum temperature of the surface gradually decreased, while the minimum temperature gradually rose. Both of them had a linear relationship with NDVI, and their spatial shape was similar to a triangle, indicating that the study of drought in Beijing-Tianjin-Hebei was effective by using this spatial feature; (2) the Beijing-Tianjin-Hebei region experienced drought every year in the period of 2001–2014, and the drought was more serious in 2001, 2004, 2008, 2009, 2011 and 2012; (3) The drought in the Beijing-Tianjin-Hebei region was widespread, and the severely arid regions were mainly concentrated in the southern and central regions. In terms of drought intensity, the most frequent occurrences in the period of 2001–2014 were Xingtai, Hengshui, Shijiazhuang, and Handan, and the annual drought in 14 years; the least number of occurrences was Chengde, a total of 4 times; the number of occurrences was second only to Chengde, Tangshan, Zhangjiakou, Qinhuangdao, a total of 7 times. Our results indicated that the Beijing-Tianjin-Hebei region was prone to drought and the drought degree was severe.
Highlights
As one of the most complicated climate disasters that have the most serious impact on human society, drought has the characteristics of high frequency, long duration and wide range of influence, which is an important problem that plagues the development of today's society (Liu et al, 2019)
Goward and Hope used NOAA-AVHRR data to find that the Normalized Difference Vegetation Index (NDVI) and Surface Temperature (Ts) vary with soil moisture (Goward, Hope, 1989); Price and Carlson et al The scatter plots showing NDVI as the abscissa and Ts as the ordinate are generally triangular (Price, 1990; Carlson et al, 1994); Nemani, Moran, etc. further discover that the feature space of Ts-NDVI is trapezoidal (Nemani et al, 1993; Moran et al, 1994); eventually Sandholt et al The Temperature Vegetation Dryness Index (TVDI) was proposed and used as an important indicator for monitoring drought by remote sensing (Sandholt et al, 2002)
Qi et al used TVDI to evaluate the distribution of drought levels across the country and carried out drought monitoring, and achieved good results (Qi, 2004); Chen et al compared the drought monitoring results of TVDI with the research situation and found that TVDI can monitor the drought well in time and accurately evaluate the drought situation of the grassland. (CHEN et al, 2013); Bai uses the normalized vegetation index NDVI and the enhanced vegetation index EVI and the surface temperature to construct the temperature-vegetation feature space, and finds that the TVDI calculated by the two vegetation indices is inversion of soil moisture
Summary
As one of the most complicated climate disasters that have the most serious impact on human society, drought has the characteristics of high frequency, long duration and wide range of influence, which is an important problem that plagues the development of today's society (Liu et al, 2019). The analysis of the spatial and temporal changes of drought in the Beijing-Tianjin-Hebei region is of great significance for alleviating the loss of drought disasters, rationally planning limited water resources and ensuring its economic and social development. (CHEN et al, 2013); Bai uses the normalized vegetation index NDVI and the enhanced vegetation index EVI and the surface temperature to construct the temperature-vegetation feature space, and finds that the TVDI calculated by the two vegetation indices is inversion of soil moisture. Both have higher precision (Bai, 2014). The drought in the Beijing-Tianjin-Hebei region was monitored by the TVDI model, and the spatial and temporal distribution of drought in the Beijing-Tianjin-Hebei region from 2001 to 2014 was analyzed
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