Research on heatwaves has gained significant impetus over the past decade due to a warming planet and rapid 21st century urbanization. This study examines driving factors influencing heatwave trends and interannual variability across Southern California (SoCal) from 1950–2020. Inland urban areas of Los Angeles county are the most susceptible to heatwaves with strong increasing trends in frequency, duration, and intensity that are closely tied to nighttime warming. Coastal and rural areas are less impacted but show a significant increase in heatwave frequency over the past two decades. Heatwave nighttime temperatures combined with high humidity have been increasing at a rapid rate of ~1°C/decade since the 1980s—elevating heat stress and mortality risk to vulnerable urban communities. The increased nighttime humidity is associated with an anomalous moisture source off the coast of Baja California that has intensified over the past decade and is linked to ocean warming trends and changes in the California current system. Heatwaves are starting earlier and ending later in the year for urban regions. This augments public health risks and sets the stage for more intense fall wildfires by enhancing the drying of fuels. Droughts and heatwaves are strongly linked, particularly in inland urban and rural areas that have a high statistical probability of heatwaves increasing in frequency (42%), duration (26%), and daily mean temperature (2.2%) during severe drought conditions. Better understanding of heatwave climate drivers and underlying physical processes could help with prediction skill, in addition to providing effective data‐driven recommendations for mitigation efforts in SoCal's vulnerable urban regions.

中文翻译：

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整个南加州热浪指标的上升趋势

在过去的十年中，由于地球变暖和21世纪的快速城市化，对热浪的研究获得了巨大的推动力。这项研究研究了影响1950年至2020年整个南加州（SoCal）热浪趋势和年际变化的驱动因素。洛杉矶县的内陆城市地区最容易受到热浪的影响，其热浪的频率，持续时间和强度都与夜间变暖密切相关。沿海和农村地区受到的影响较小，但在过去的二十年中，热浪频率显着增加。自1980年代以来，热浪夜间温度与高湿度的结合一直以大约1°C /十年的速度快速增加，从而使脆弱的城市社区面临着热应激和死亡风险。夜间湿度的增加与加利福尼亚下加利福尼亚州沿海的异常水分源有关，该异常源在过去十年中加剧了，并与海洋变暖趋势和加利福尼亚现行系统的变化有关。城市地区的热浪开始较早，结束于今年晚些时候。这增加了公共健康风险，并通过增强燃料干燥为更剧烈的秋季野火奠定了基础。干旱和热浪有着密切的联系，特别是在内陆城市和农村地区，在严重干旱条件下，热浪的发生频率（42％），持续时间（26％）和日平均温度（2.2％）升高的统计概率很高。更好地了解热浪气候驱动因素和潜在的物理过程可能有助于预测技能，