Drought is a type of natural disaster that has the most significant impacts on agriculture. Regional drought monitoring based on remote sensing has become popular due to the development of remote sensing technology. In this study, vegetation condition index (VCI) data recorded from 1982 to 2010 in agricultural areas of China were obtained from advanced very high resolution radiometer (AVHRR) data, and the temporal and spatial variations in each drought were analyzed. The relationships between drought and climate factors were also analyzed. The results showed that from 1982 to 2010, the agricultural areas that experienced frequent and severe droughts were mainly concentrated in the northwestern areas and Huang-Huai Plain. Moreover, the VCI increased in the majority of agricultural areas, indicating that the drought frequency decreased over time, and the decreasing trend in the southern region was more notable than that in the northern region. A correlation analysis showed that temperature and wind velocity were the main factors that influenced drought in the agricultural areas of China. From a regional perspective, excluding precipitation, the climate factors had various effects on drought in different regions. However, the correlation between the VCI and precipitation was low, possibly due to the widespread use of artificial irrigation technology, which reduces the reliance of agricultural areas on precipitation.

Abstract. Information concerning the spatial and temporal characteristics of vegetative drought is essential for decision-making and for many environmental and agricultural applications. This study presents a comprehensive spatio-temporal analysis of vegetative drought conditions that used the vegetation condition index (VCI) data product obtained from NOAA/AVHRR (National Oceanic and Atmospheric Administration/Advanced Very High Resolution Radiometer) to reveal the vegetative drought patterns across China from 1981 to 2015. Considering the characteristics of VCI as drought indicators, multiple methods were designed for these analyses, including drought frequency analysis, trend analysis, anomaly index analysis, and Mann-Kendall testing. The results show that China is a country with high vegetative drought frequency, but that most areas experienced only slight or moderate periods of drought. In addition, drought has obvious seasonal and geographical differences and occurs with greater frequencies in regions that are highly affected by monsoons such as the northern and southern regions-particularly in the spring and autumn. In contrast, vegetative drought frequencies in regions less affected by monsoons such as the Tibetan Plateau and the northwestern regions were much lower except in northern Sinkiang, eastern Inner Mongolia, and southern Tibet. During 1981-2015, the VCI had an increasing trend in most areas of China (except in the southern region, where it decreased), indicating a reduced frequency of vegetative drought throughout the country. Moreover, the trend was wavelike rather than a one-way change and could be divided into four phases: (1) a slowly increasing phase from 1981 to 1990, (2) an intensively fluctuating phase from 1991 to 2000, (3) a steadily increasing phase from 2001 to 2010, and (4) a slowly decreasing phase after 2010. Mann-Kendall analysis further suggested that upward trends of the VCI were more evident in spring and autumn than in summer and that both trends mutated in 1997. Specifically, the trend reached the 0.05 level of significance in the spring.

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