Does Drought Show a Significant Decreasing Trend From 1961 to 2017 in Northern China?

Abstract

Understanding the variation of drought is essentially important in climate change and risk assessment. Based on the monthly meteorological data at 321 stations, this study computed the Standardized Precipitation Evapotranspiration Index (SPEI), which was estimated using the potential evapotranspiration (PET) with the Penman–Monteith equation. The trends, affected-area, duration, and frequency of drought was determined using the piecewise linear regression method (LRM) for 1961–2017 over northern China. The results found that (1) drought displayed a wetting trend in 1961-2017 at a rate of 0.05/10a (p > 0.05), which generally occurred in winter and in most study areas, particularly in the Xinjiang Uygur Autonomous Region. In contrast, an apparent drying trend occurred on the Loess Plateau. (2) The LRM identified that the turning point (TP) for trends occurred in 1990; the annual SPEI had been increasing pre-1990 and decreasing post-1990. This was especially the case in the Xinjiang Uygur Autonomous Region, Tibet, Gansu, and Inner Mongolia, consistent with patterns of seasonal drought at their respective TP apart from autumn. (3) From 1961 to 2017, the drought-affected area decreased at a rate of −1.69%/10a (p < 0.05). This area decreased before the TP and increased after the TP at different drought levels. The seasonal drought also showed decreasing trend, particularly in winter. (4) The highest frequency and duration of drought occurred in the Loess Plateau and Xinjiang Uygur Autonomous Region, respectively, although it decreased post-1990. These findings suggest that long-term trends in drought were not significant in northern China during 1961–2017. Although the severity, frequency, and duration of drought decreased post-1990, the recent drying trend and increase in the drought-affected area should not be dismissed.