Occurrence and Reverse Transport of Severe Dust Storms Associated with Synoptic Weather in East Asia

The range and time of the environmental effects of Asian dust are closely dependent on the pathways and the speed of dust plume movement. In this study, the occurrence and movement of two dust storms in China in May 2017 were examined by using open space- and ground-based measurement data and the backward trajectories of dust plumes. Results from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data showed that the dust storms were caused by the rapid coupling development of Mongolian cyclones and Asian highs. After the dust plumes arrived at the Southeastern China in the first dust event, the stable weather conditions and the Asian high slowed down the movement of the plumes, leading to the gradual diffusion of dust particles. Moreover, the Asian high in the first event and the Huabei low (a low-pressure system in North China Plain) in the second altered the movement direction of the dust plumes from southward to northward, which we denote as the dust reverse transport (DRT). The DRT occurred only within the lower troposphere even though dust plumes could extended to 5-10 km in vertical direction. Statistical results of 28 spring dust events occurred in 2015-2018 showed that all these dust storms were triggered by Mongolian cyclones and/or Asian highs, and approximately 39% moved as the DRT, indicating about one third of severe spring dust storms could influence larger areas or longer time than the remained ones.