Drought variability at various timescales over Yunnan Province, China: 1961–2015
Droughts have substantial impacts on agriculture and ecosystems, resulting in tremendous economic losses and social damage. This work investigated the spatiotemporal variabilities of drought across Yunnan province from 1961 to 2015. The drought conditions were identified according to the standardized precipitation evapotranspiration index (SPEI) at various timescales based on the monthly precipitation and air temperature data collected at 122 meteorological stations. Mann–Kendall and Pettitt tests were adopted to analyze the trends and change points in the time series. The results showed that (1) the mean annual precipitation decreased by 15 mm/decade (p < 0.1), and the temperature increased significantly by 0.19 °C/decade (p < 0.01), indicating that Yunnan province has experienced a warming-drying climatic trend. (2) The annual SPEI exhibited a significant decreasing trend at a rate of − 0.16/decade (p < 0.01), and a change point was detected in 2002 (p < 0.05). Significant downward trends were found in the summer (p < 0.01) and autumn (p < 0.05) for the seasonal SPEI, with rates of − 0.13 and − 0.11/decade, respectively. Spatially, significant drying trends were observed in the Lancang and Pearl River Basins. (3) Higher frequencies of extreme and severe drought occurred with the extension of the timescale, particularly in central, northwestern, eastern, and northeastern Yunnan. With regard to inter-decadal variations, the drought frequencies at the 1-, 3-, 6-, and 12-month timescales generally increased and displayed fluctuating behavior. Moreover, the extent of the drought coverage area gradually expanded during the study period, especially after the early 2000s. (4) Increasingly frequent droughts have had substantial impacts on streamflow and agriculture over the past decade. The increase in droughts is associated with the weakening of the Asian summer monsoon, which has resulted in less precipitation in Yunnan. These results could be employed as references for the assessment of droughts and mitigation of drought disasters in Yunnan province.
We would like to acknowledge the anonymous reviewers for their valuable comments and advice.
This work is jointly supported by the National Natural Science Foundation of China (Grant No. 41661099), National Key R&D Program of China (Grant No. 2016YFA0601601), Applied Basic Research Programs of Yunnan Province (Grant No. 2017FB071), and Climate Change Special Fund of the China Meteorological Administration (Grant No. CCSF201736).
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