Spatiotemporal Variations of Drought and the Related Mitigation Effects of Artificial Precipitation Enhancement in Hengyang-Shaoyang Drought Corridor, Hunan Province, China

It is important to reveal the spatial and temporal variations of drought and evaluate the alleviating effects of artificial precipitation on drought severity, as it will contribute immensely to the formulation of drought prevention and mitigation measures and the provision of guidance to artificial precipitation enhancement operation. Based on the monthly precipitation data of 28 meteorological stations in Hengyang-Shaoyang Drought Corridor (HSDC) from 1960 to 2019, the standardized precipitation index (SPI) at multiple time scales were calculated to estimate drought frequency, drought station ratio, and drought intensity. Then the spatiotemporal variations of drought in the study area were unveiled, and the effects of artificial precipitation enhancement were evaluated in line with the relevant data from 2005 to 2019. The results show that at the annual scale, drought occurred in 3/4 of past sixty years in the study area, where almost 1/3 of such years experienced area-wide droughts. Drought coverage in HSDC exhibited a decreasing trend, but drought intensity, as well as the number of area-wide droughts and regional droughts showed an increasing one. Mild and moderate droughts occurred in an extensive part of the HSDC, whereas severe and extreme droughts were mainly found in a few stations. At the seasonal scale, winter drought occurred most frequently, followed by summer and autumn droughts, while spring drought events had the lowest frequency. Overall, drought is more serious in spring, autumn, and winter, but less severe in summer; although drought intensity decreased slightly in summer, both its intensity and coverage showed an increasing trend in other seasons. At the monthly scale, the ratio of positive to negative SPI values in HSDC was basically balanced in the past six decades, exhibiting no distinct variation characteristics. In addition, artificial precipitation enhancement effectively eased monthly and even seasonal drought in HSDC. These findings, which fully reflect the characteristics of drought in the study area, can also raise awareness of the contribution that artificial precipitation could make to drought mitigation, which in turn will contribute to the formulation of appropriate strategies for climate change mitigation and adaptation.