During the summer of 2021, the North American Pacific Northwest was affected by an extreme heatwave that broke previous temperature records by several degrees. The event caused severe impacts on human life and ecosystems, and was associated with the superposition of concurrent drivers, whose effects were amplified by climate change. We evaluate whether this record-breaking heatwave could have been foreseen prior to its observation, and how climate change affects North American Pacific Northwest worst-case heatwave scenarios. To this purpose, we use a stochastic weather generator with empirical importance sampling. The generator simulates extreme temperature sequences using circulation analogues, chosen with an importance sampling based on the daily maximum temperature over the region that recorded the most extreme impacts. We show how some of the large-scale drivers of the event can be obtained form the circulation analogues, even if such information is not directly given to the stochastic weather generator.

中文翻译：

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通过模拟重要性采样模拟 2021 年北美西部热浪

2021年夏季，北美太平洋西北地区受到极端热浪的影响，温度打破了之前的记录数度。该事件对人类生活和生态系统造成了严重影响，并与并发驱动因素的叠加有关，其影响因气候变化而放大。我们评估了在观测之前是否可以预见到这场破纪录的热浪，以及气候变化如何影响北美太平洋西北地区最坏的热浪情景。为此，我们使用具有经验重要性采样的随机天气生成器。该发生器使用循环模拟来模拟极端温度序列，循环模拟是根据记录最极端影响的区域的每日最高温度进行重要采样而选择的。我们展示了如何从循环类似物中获得事件的一些大规模驱动因素，即使这些信息没有直接提供给随机天气生成器。