Abstract
Drought and extreme precipitation events can have major environmental and socioeconomic impacts. Yet, how drought and wetness are changing in China in the context of climate change is still under debate. Here, the standardized precipitation evapotranspiration index (SPEI) was calculated based on high-quality and more densely distributed daily meteorological observation data from 655 stations across China during the period of 1965–2017. National and regional trends in drought and wetness and their various characteristics, including intensity, duration, frequency, and percentage of area affected, were investigated at multiple timescales. We found that (1) China as a whole has undergone a significant (p < 0.01, trend significant at the level of 0.01) wetting trend, with an annual SPEI increase of 0.5 per decade from 1965 to 2017. A seasonal wetting trend was also observed, with summer being particularly significant (p < 0.01). (2) Regionally, each subregion also showed a wetting trend during the study period except for southwest China, and these wetting trends were significant in the western region of northwest China (p < 0.05, trend significant at the level of 0.05), the Tibetan Plateau (p < 0.05), and eastern China (p = 0.06). (3) Decadal trends in drought and wetness intensity, frequency, duration, and affected areas indicated that the drought events also became more severe and more frequent in the last two decades, and the areas showing drying trends were mainly located in southwest China (especially for the autumn drought) and the southwestern parts of eastern northwest China (spring drought). Our results highlight the fact that although a wetting trend was observed in most regions of China, the frequent occurrence of severe drought in southwest China and the southwestern parts of eastern northwest China still present a considerable threat to both the environment and society. Therefore, how to effectively coordinate the allocation of regional water resources to cope with drought risk under future climate change will be particularly important.
Highlights
Global warming coupled with intensifying human activities are expected to accelerate the global hydrological cycle [1,2], and alter the spatiotemporal patterns of precipitation, which in turn will result in an increased occurrence of extremes, including severe droughts or floods, in many regions of the world [3,4]
Regarding trends in the decadal wetness characteristics, stations that showed increases in wetness intensity, frequency, and duration accounted for 65.3%, 68.3%, and 75.8% of the total stations, respectively; these stations showed roughly the same spatial patterns and were located mainly in the frequency occurred at 44 stations, which were located mainly in WNW and E China and Tibet
Even as an increase in air temperature has been observed across China in the last few decades, several regions of China have reported that the potential evapotranspiration (PET) or pan evaporation has shown a steady downward trend [31,32], which was identified by our results (Figure 3b)
Summary
Global warming coupled with intensifying human activities (e.g., water reservoir construction, urbanization, and deforestation) are expected to accelerate the global hydrological cycle [1,2], and alter the spatiotemporal patterns of precipitation, which in turn will result in an increased occurrence of extremes, including severe droughts or floods, in many regions of the world [3,4]. Little attention has been paid to the seasonal trends in drought and wetness, which can reflect more important roles in regulating agricultural production [17,18] To resolve these discrepancies and to provide an improved estimate of changes in drought and wetness in China over the past 53 years based on a better understanding of the physical mechanism underlying the occurrence of drought and wetness, we first analyzed the yearly and seasonal trends in the SPEI, in which the PET was calculated by the Penman–Monteith equation, at national and regional scales. We investigated the changes and decadal trends in various drought–wetness characteristics, including the intensity, frequency, duration, and percentage of affected areas, from 1965 to 2017 with the aim of further improving our understanding of warming-induced drought and wetness changes in China
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