Circulation and Soil Moisture Contributions to Heatwaves in the United States
Circulation and Soil Moisture Contributions to Heatwaves in the United States
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DOI：
10.1175/jcli-d-21-0156.1
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发表时间：
2022-12-15
影响因子：
4.9
通讯作者：
Simpson, Isla R.
中科院分区：
文献类型：
--
作者：
Horowitz, Russell L.;McKinnon, Karen A.;Simpson, Isla R.
极端高温事件对人类健康、生产力和粮食供应构成威胁，因此了解其驱动因素对适应和恢复能力至关重要。众所周知，反气旋环流和某些准静止的罗斯比波模式与热浪同时发生，土壤水分不足加剧了某些地区的极端高温。然而，这两个因素在引起热浪中的相对作用尚不清楚。本文在社区地球系统模式第1版（CESM1）工业化前控制模拟中，使用构建的环流类比来估计大气环流对美国热浪的贡献。在考虑了由环流解释的热浪分量后，我们探讨了剩余温度异常与土壤湿度的关系。我们发现环流解释了美国东部和西部85%以上的热浪温度异常，但在美国中部仅解释了75%-85%。在该地区，热浪前一周的土壤湿度与热浪强度之间存在显著的负相关，这解释了额外的方差。此外，对于美国中部最炎热的热浪来说，在热浪开始前一个月，温度正异常和土壤湿度负异常就很明显了。这些结果提供了证据，表明陆地-大气的正反馈可能会放大美国中部的热浪，并表明陆地和大气对热浪发展的相对重要性存在地理异质性。对CESM1大集合的未来环流和土壤湿度的分析表明，在美国部分地区，两者都可能趋向于更大的热浪可能性。
Extreme heat events are a threat to human health, productivity, and food supply, so understanding their drivers is critical to adaptation and resilience. Anticyclonic circulation and certain quasi-stationary Rossby wave patterns are well known to coincide with heatwaves, and soil moisture deficits amplify extreme heat in some regions. However, the relative roles of these two factors in causing heatwaves is still unclear. Here we use constructed circulation analogs to estimate the contribution of atmospheric circulation to heatwaves in the United States in the Community Earth System Model version 1 (CESM1) preindustrial control simulations. After accounting for the component of the heatwaves explained by circulation, we explore the relationship between the residual temperature anomalies and soil moisture. We find that circulation explains over 85% of heatwave temperature anomalies in the eastern and western United States but only 75%-85% in the central United States. In this region, there is a significant negative correlation between soil moisture the week before the heatwave and the strength of the heatwave that explains additional variance. Further, for the hottest central U.S. heatwaves, positive temperature anomalies and negative soil moisture anomalies are evident over a month before heatwave onset. These results provide evidence that positive land-atmosphere feedbacks may be amplifying heatwaves in the central United States and demonstrate the geographic heterogeneity in the relative importance of the land and atmosphere for heatwave development. Analysis of future circulation and soil moisture in the CESM1 Large Ensemble indicates that, over parts of the United States, both may be trending toward greater heatwave likelihood.