干旱气象 ›› 2025, Vol. 43 ›› Issue (5): 678-688.DOI: 10.11755/j.issn.1006-7639-2025-05-0678

• “加州山火与干旱”专栏 • 上一篇    下一篇

2024年7月美国加利福尼亚州山火与干旱和高温等极端气象条件的关系及大气环流成因

赵采玲1(), 杨金虎1, 岳平1, 颜鹏程1(), 李忆平1, 李红1, 李丹华2   

  1. 1.中国气象局兰州干旱气象研究所,甘肃省干旱气候变化与减灾重点实验室,中国气象局干旱气候变化与减灾重点实验室,甘肃 兰州 730020
    2.兰州区域气候中心,甘肃 兰州 730020
  • 收稿日期:2025-01-16 修回日期:2025-04-14 出版日期:2025-10-31 发布日期:2025-11-09
  • 通讯作者: 颜鹏程(1987—),男,江苏盐城人,副研究员,主要从事气候预测研究。E-mail: yanpc@iamcma.cn
  • 作者简介:赵采玲(1989—),女,甘肃金昌人,副研究员,主要从事陆气相互作用研究。E-mail: zhaocl@iamcma.cn
  • 基金资助:
    气象能力提升联合研究专项重点项目(22NLTSZ003);国家自然科学基金项目(42375085);国家自然科学基金项目(42205050);国家自然科学基金项目(42375039)

The relationship between large-scale atmospheric circulations, extreme meteorological conditions, and the severe wildfire outbreak in California, USA during July 2024

ZHAO Cailing1(), YANG Jinhu1, YUE Ping1, YAN Pengcheng1(), LI Yiping1, LI Hong1, LI Danhua2   

  1. 1. Institute of Arid Meteorology, China Meteorological Administration, Key Laboratory of Arid Climate Change and Reducing Disaster of Gansu Province, Key Laboratory of Arid Climate Change and Reducing Disaster of CMA, Lanzhou 730020, China
    2. Lanzhou Regional Climate Center, Lanzhou 730020, China
  • Received:2025-01-16 Revised:2025-04-14 Online:2025-10-31 Published:2025-11-09

摘要:

2024年7月加州北部爆发的特大山火在极端高温与强风的共同作用下迅速蔓延,造成严重损失。本文利用美国干旱监测的干旱程度和面积指数(Drought Severity and Coverage Index,DSCI)、欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts, ECMWF)发布的ERA5(ECMWF Reanalysis v5)再分析资料和美国国家海洋和大气管理局(National Oceanic and Atmospheric Administration,NOAA)提供的海温等多源数据,分析山火爆发前后的气象条件与环流背景,可为极端气候背景下山火预警与防控提供科学依据。结果表明:2024年7月加州山火爆发是极端气象条件导致的结果,持续数周的高温(日最高气温达32.1 ℃)、极低湿度(平均相对湿度<50%)和持续干旱(DSCI>26.0)使植被高度易燃。环流系统极端异常加剧了高温干旱,北美西海岸持续受高压环流控制,局地强风加速了山火的空间传播。2024年厄尔尼诺事件(Niño 3.4区正异常)通过遥相关作用增强高压系统,抑制冬季降水并延长干旱期,热带东太平洋暖海温使得哈德莱环流增强,加强了加利福尼亚州的下沉气流,最终形成“高温-低湿-干旱”的耦合模式,显著增加山火面积和持续时间。

关键词: 加利福尼亚山火, 极端气象条件, 高温和干旱, 副热带高压, 厄尔尼诺

Abstract:

A catastrophic wildfire on 24 July 2024 erupted in northern California, USA, rapidly intensifying under the synergistic effects of extreme heat and strong winds, leading to significant ecological and socioeconomic losses. Multi-source data, including the drought severity and coverage index (DSCI), ERA5 reanalysis datasets from the European Centre for Medium-Range Weather Forecasts (ECMWF), and sea surface temperature (SST) data provided by the National Oceanic and Atmospheric Administration (NOAA), were utilized to analyze the meteorological conditions and circulation patterns before and after the wildfire outbreak. The findings can provide a scientific basis for wildfire early warning and prevention under extreme climate conditions. The main conclusions are as follows: The July 2024 California wildfire was a result of extreme meteorological conditions, where weeks of persistent high temperatures (daily maximum temperature reaching 32.1 ℃), extremely low humidity (average relative humidity less than 50%), and sustained drought (DSCI greater than 26.0) rendered vegetation highly flammable. Extremely anomalous circulation systems exacerbated the high temperatures and drought, with the North American west coast persistently controlled by high-pressure circulation, and localized strong winds accelerated the spatial spread of the wildfire. The 2024 El Niño event (positive anomaly in the Niño 3.4 region) enhanced the high-pressure system through teleconnection effects, suppressed winter precipitation, prolonged the drought period, and warm sea surface temperatures in the eastern tropical Pacific intensified the Hadley circulation, strengthening the subsidence airflow over California, ultimately forming a coupled “high temperature-low humidity-drought” pattern that significantly increased the wildfire area and duration.

Key words: California wildfire, extreme meteorological conditions, high temperature and drought, subtropical high, El Niño

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