Regional transport patterns for heavy PM2.5 pollution driven by strong cold airflows in Twain-Hu Basin, Central China

Abstract

Passages of strong cold airflow can quickly purge air pollutants over source region, e.g. North China Plain (NCP), while regional transport of air pollutants from source region would exacerbate air quality in the receptor region of Twain-Hu Basin (THB), due to the cold airflows modulated by atmospheric circulations over China. In this study, nine heavy pollution events (HPEs) in THB, Central China during the winters of 2015–2019 were identified for investigating the regional transport patterns of air pollutants from Central and Eastern China (CEC) to THB driven by strong cold airflows. Once regional transport of air pollutants from the CEC source regions was triggered by strong northerlies, PM2.5 pollution parcels then converged in the downwind THB receptor region through a dominant dynamic mechanism for most HPEs (66.7%) with downward airflow, which generally resulted in long durations of high PM2.5 concentrations and the impacted areas were modulated by synoptic patterns over the CEC. Non-dominant transport patterns were also observed with a cyclonic circulation of high wind speeds or a local stagnation of cold air over the THB, contributing to the highest and shortest PM2.5 peak or small impacted areas limited to the northern THB, respectively. It was estimated that the regional transport of PM2.5 from non-local regions accounted for 51.0%–85.7% of PM2.5 concentrations during the HPEs at Wuhan, revealing the dominance of regional transport of air pollutants from CEC to the THB with the meteorological drivers.