Compound spatial extremes of heatwaves and downstream air pollution events in East Asia

In light of increasing climate hazards globally that pose risk to public health, the compounded effects of two major hazards, heatwaves and air pollution, have become a focal point for environmental and health research. This study explores the intricate relationship between extreme temperature events in North China (NC) and South China (SC) – two prominent areas of aerosol exposure in East Asia – and the associated changes in aerosol optical depth (AOD) across the region. The heatwave events and regional AOD distribution revealed distinct patterns in their respective regions from June to September. Both NC and SC showed reduced AOD during heatwave events, while downstream regions experienced increased AOD levels. From the perspective of heatwaves in NC and SC, we present a more holistic picture of how large-scale modulators contribute to inducing air pollution hazards across East Asia. The analysis revealed a link between blocking high-pressure system and heatwave occurrences in NC, while a dominant Rossby wave train, influenced by the South China Sea, was identified as a major modulator in SC. Additionally, other large-scale circulatory systems, such as the Western Pacific Subtropical High, the East Asian jet stream, and the South Asian High, also play crucial roles in shaping these events. This suggests the potential for predicting downstream AOD events. The study underscores the importance of understanding the interconnectedness of meteorological and air quality phenomena to mitigate the adverse environmental impacts in East Asia.