Hot extremes have become drier in the United States Southwest
Hot extremes have become drier in the United States Southwest
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DOI：
10.1038/s41558-021-01076-9
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发表时间：
2021-06
影响因子：
30.7
通讯作者：
K. McKinnon;A. Poppick;I. Simpson
中科院分区：
文献类型：
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作者：
K. McKinnon;A. Poppick;I. Simpson
夏季极端高温的影响是由湿度介导的。由于人为造成的气候变化而导致的温度升高通常会增加比湿度;然而，目前尚不清楚极端湿度如何变化，特别是在气候干燥（低湿度）地区。在这里，我们表明，在过去的70年里，美国西南部夏季干燥日（这里定义为7月至9月）的比湿度有所下降，最大的下降与最热的温度同时发生。炎热干燥的夏季有着极低的蒸散量，这与夏季土壤湿度低有关。夏季土壤湿度最近的减少是由6月土壤湿度的下降，而年际变化是由夏季降水控制。由于耦合模式相互比较项目第6阶段（CMIP 6）到2100年土壤湿度和降水趋势的大范围传播，未来西南部炎热干燥天气的预测是不确定的。
The impacts of summer heat extremes are mediated by humidity. Increases in temperatures due to human-caused climate change are generally expected to increase specific humidity; however, it remains unclear how humidity extremes may change, especially in climatologically dry (low-humidity) regions. Here we show that specific humidity on dry days during summer (defined here as July–September) has decreased over the past seven decades in the United States Southwest, and that the greatest decreases co-occur with the hottest temperatures. Hot, dry summers have anomalously low evapotranspiration that is linked to low summer soil moisture. The recent decrease in summer soil moisture is explained by declines in June soil moisture, whereas the interannual variability is controlled by summer precipitation. Future projections of hot, dry days in the Southwest are uncertain due to the large spread in the Coupled Model Intercomparison Project phase 6 (CMIP6) trends in soil moisture and precipitation through 2100.