Understanding the atmospheric circulation patterns responsible for severe air pollution events in East Asia is important because East Asia is one of the most polluted regions in the world, particularly during the boreal winter (December-January-February). Here, by conducting GEOS-Chem simulation with fixed anthropogenic emission sources, we found that there exist three typical atmospheric circulation patterns conducive to leading to high concentrations of particulate matter with a diameter less than or equal to 2.5 μm (PM) in East Asia. These atmospheric circulation patterns are characterized by weakened horizontal winds, which allows PM to accumulate, and by enhanced relative humidity, which can favor secondary formation of PM. The occurrence of these atmospheric circulation patterns is associated with increased sea ice cover over the Barents Sea and heavy precipitation over the tropical western Indian Ocean. The existence of these atmospheric circulation patterns among typical atmospheric circulation patterns indicates high PM days in East Asia are unavoidable given current level of anthropogenic emissions in the region. This conclusion indicates that sustained efforts to reduce anthropogenic emission sources in East Asia should be warranted to avoid high PM days.

中文翻译：

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东亚地区存在典型的冬季大气环流模式导致PM2.5高浓度日数

了解造成东亚严重空气污染事件的大气环流模式非常重要，因为东亚是世界上污染最严重的地区之一，特别是在寒带冬季（12月至1月至2月）。在这里，通过对固定人为排放源进行GEOS-Chem模拟，我们发现东亚地区存在三种典型的有利于导致直径小于或等于2.5μm颗粒物（PM）高浓度的大气环流模式。这些大气环流模式的特点是水平风减弱，使 PM 积聚，而相对湿度增加，有利于 PM 的二次形成。这些大气环流模式的发生与巴伦支海海冰覆盖面积的增加和热带西印度洋的强降水有关。这些大气环流模式在典型大气环流模式中的存在表明，考虑到该地区目前的人为排放水平，东亚地区的高PM天数是不可避免的。这一结论表明，东亚地区应持续努力减少人为排放源，以避免出现高 PM 天气。