Abstract The Intergovernmental Panel on Climate Change (IPCC) reports that the changes in extreme events are expected to be detected earlier than changes in climate averages. Hot temperature extremes in the United States cause important economical, societal, and environmental impacts. Thus, the climatology of hot extremes and heat waves (HWs) merits further examination. Spatiotemporal trends of five extreme temperature indicators were investigated for the period 1948–2017 for the Mississippi River Basin (MRB), which covers approximately 41% of the Contiguous United States. A hot extreme was identified using the 90th percentile threshold and a HW was defined as two or more consecutive hot temperature extreme days. Results suggest that the western, north-western, southern, and northern parts of the MRB are regions with a growing risk of extreme temperatures with more frequent and longer hot events. Change in the eastern part of the MRB suggests a smaller risk with a general downward trend in HWs. Change-point analysis indicates that these climatic data exhibit nonstationarity. A significant increase happened starting in 1994 in the percentage of area with a HW longer than 10 consecutive days. Frequency and length of HWs were greater during El Nino years. However, this finding is not statistically significant. An increase in HW duration and frequency can impact water availability, human and animal health, agriculture and the economy. Results from this study assist in finding hotspots where changing extreme conditions have happened and where society may need to make adjustments related to water use, human outdoor activities and agricultural practices.

中文翻译：

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密西西比河流域极端高温和热浪的评估

摘要 政府间气候变化专门委员会 (IPCC) 报告称，极端事件的变化预计会比气候平均值的变化更早地被发现。美国的极端高温会造成重要的经济、社会和环境影响。因此，极端炎热和热浪 (HW) 的气候学值得进一步研究。调查了 1948 年至 2017 年期间密西西比河流域 (MRB) 的五个极端温度指标的时空趋势，该流域覆盖了美国本土约 41% 的地区。使用第 90 个百分位数阈值确定极端炎热，并将 HW 定义为连续两个或更多极端高温日。结果表明，西部、西北、南部、和 MRB 北部是极端温度风险越来越大的地区，高温事件更加频繁和持续时间更长。MRB 东部的变化表明风险较小，硬件总体呈下降趋势。变点分析表明这些气候数据表现出非平稳性。从 1994 年开始，HW 连续超过 10 天的地区百分比显着增加。在厄尔尼诺年期间，HW 的频率和长度更大。然而，这一发现在统计上并不显着。HW 持续时间和频率的增加会影响可用水量、人类和动物健康、农业和经济。这项研究的结果有助于找到发生极端条件变化的热点，以及社会可能需要做出与用水相关的调整的热点，