Zhuang Yizhou, Fu Rong, Lisonbee Joel, Sheffield Amanda M, Parker Britt A, Deheza Genoveva
Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, Los Angeles, CA 90095, USA.
NOAA National Integrated Drought Information System, Boulder, CO 80305, USA.
Sci Adv. 2024 Nov 8;10(45):eadn9389. doi: 10.1126/sciadv.adn9389. Epub 2024 Nov 6.
Historically, meteorological drought in the western United States (WUS) has been driven primarily by precipitation deficits. However, our observational analysis shows that, since around 2000, rising surface temperature and the resulting high evaporative demand have contributed more to drought severity (62%) and coverage (66%) over the WUS than precipitation deficit. This increase in evaporative demand during droughts, mostly attributable to anthropogenic warming according to analyses of both observations and climate model simulations, is the main cause of the increased drought severity and coverage. The unprecedented 2020-2022 WUS drought exemplifies this shift in drought drivers, with high evaporative demand accounting for 61% of its severity, compared to 39% from precipitation deficit. Climate model simulations corroborate this shift and project that, under the fossil-fueled development scenario (SSP5-8.5), droughts like the 2020-2022 event will transition from a one-in-more-than-a-thousand-year event in the pre-2022 period to a 1-in-60-year event by the mid-21st century and to a 1-in-6-year event by the late-21st century.
从历史上看，美国西部（WUS）的气象干旱主要是由降水不足导致的。然而，我们的观测分析表明，自2000年左右以来，地表温度上升以及由此产生的高蒸发需求对美国西部干旱的严重程度（62%）和覆盖范围（66%）的影响超过了降水不足。根据观测和气候模型模拟分析，干旱期间蒸发需求的增加主要归因于人为变暖，这是干旱严重程度和覆盖范围增加的主要原因。2020 - 2022年美国西部前所未有的干旱就体现了干旱驱动因素的这种转变，高蒸发需求占其严重程度的61%，而降水不足占39%。气候模型模拟证实了这种转变，并预测在以化石燃料为动力的发展情景（SSP5 - 8.5）下，像2020 - 2022年这样的干旱将从2022年之前一千多年一遇的事件转变为到21世纪中叶60年一遇的事件，到21世纪末变为6年一遇的事件。
