资源环境科技发展态势分析平台

This study employs the self-organizing map classification to track wintertime PM_2.5 pollutions in Delhi under four atmospheric circulation patterns during 2013-2020. We found that the most polluted circulation pattern was characterized by a northward shift in the subtropical jet stream and a northward intrusion of the subtropical high, leading to descending anomalies from the upper troposphere to the near surface. Together, the resultant reduced passage of cyclones, lower planetary boundary layer, weakened near-surface winds and less precipitation contributed to wintertime PM_2.5 pollution in Delhi. Compared with the 1981-2010 mean levels, CMIP6 models project Delhi would experience 2 fewer days of severe pollution-favorable circulation pattern and 7 more days of clean-favorable circulation pattern in 2070-2099 under the shared socioeconomic pathway 5-8.5. Future decrease in the severe pollution-favorable circulation pattern may be attributed to the warming trends in sea surface temperature over the central Pacific and North Atlantic Ocean.