Analysis of a severe regional haze-fog-dust episode over North China in autumn by using multiple observation data

Abstract

The mixing of dust and haze is an important factor in the variation of fine particles. In this study, multiple observation data were used to analyze the characteristics and formation of a haze-fog-dust event that occurred in North China between November 23 and November 30 of 2018. This episode can be roughly divided into two stages, haze-fog and dust, with the transition occurring on November 27. Our analysis shows that stable weather conditions and temperature inversions in North China caused the haze-fog event (November 23–26), during which the PM2.5 concentration gradually increased. After November 27, the arrival of cold air accompanied by dust activity rendered meteorological conditions favorable to air quality in the northern part but not the central or southern part of North China. Instead, continuous adverse conditions and the dust backflow, which trapped dust aerosols in the southern part of North China for nearly two days, were responsible for high PM2.5 concentrations in Jinan and Zhengzhou after November 27 (146 and 156 µg m–3 vs. 114 and 144 µg m–3 before November 27, respectively). This study highlights the effect of dust transport on regional environmental pollution during the autumn and the winter.