1960—2016年黄土高原干旱和热浪时空变化特征

基于1960—2016年黄土高原49个气象台站日最高气温和月降水数据,论文利用百分位高温阈值和标准化降水指标对黄土高原干旱和热浪时空变化特征进行了分析,识别并探讨了干旱和热浪同时发生事件的演变规律。结果表明：① 黄土高原热浪频次整体呈增加趋势,日高温热浪增加趋势最大,增速达到0.29次/a,1995年之后增加趋势更为明显,显著增加区域集中在山西东北部、青海省东部和甘肃中南部;② 1960—2016年黄土高原旱涝指数呈下降趋势,即表现为由涝转旱,20世纪90年代初为旱涝变化的转折点,年旱涝指数下降趋势显著区占整个研究区的62%,其中黄土高原沟壑区南部、陕北南部、山西南部、甘肃东部干旱趋势较为明显;③ 干旱和热浪同时发生事件总体呈现增加趋势,增速为0.66次/10 a,其中1960—1979年呈下降趋势,降速为-0.26次/a,1980—2002年呈增加趋势,2003年之后变化趋势较为平稳;空间上,山西东部、陕北南部和甘肃东南部发生频次较高,并且显著增加区主要位于山西东北部、甘肃中东部和宁夏北部。

Spatiotemporal changes of droughts and heatwaves on the Loess Plateau during 1960-2016

Based on daily maximum temperature and monthly precipitation data of 49 meteorological stations on the Loess Plateau during 1960-2016 and using the 90th percentile of the temperature as extreme temperature thresholds and standardized precipitation index (SPI), this study examined the spatiotemporal variation characteristics of heatwaves and droughts and the dynamics of concurrent droughts and heatwaves across the Loess Plateau. The results show that: 1) The occurrence frequency of heatwaves presented an increasing trend on the Loess Plateau during the recent 57 years with a liner tendency of 0.29 times/a, of which a significant increasing trend was detected after 1995. The significantly increasing areas were mainly distributed in the northeast of Shanxi Province, eastern Qinghai Province, and southern and central Gansu Province. 2) Standardized precipitation index (SPI) showed a downward trend in the recent 57 years, indicating a trend from water-logging to drought, and the early 1990s was a turning point. Particularly, areas with the declining trend of SPI₁₂ accounted for 62% of the whole study area, and regions with significant drought were mainly distributed in the south of the gully areas of the Loess Plateau, the southern part of Northern Shaanxi, the south of Shanxi Province, and the east of Gansu Province. 3) The simultaneous occurrence frequency of droughts and heatwaves showed an overall increasing trend, with a growth rate of 0.66 times/10 a. From 1960 to 1979 it showed a declining trend of -0.26 times/a, then an increasing trend of 0.52 times/a from 1980 to 2002, while a steady increasing trend was detected after 2003. Spatially, the high incidence of droughts and heatwaves was observed in the eastern of Shanxi, the south of Northern Shaanxi, and the southwest of Gansu; areas with increasing trend were mainly concentrated in the northeast of Shanxi, central and eastern Gansu, and northern Ningxia.