Biomass Burning Plumes From Indochina Toward Southern China: Predominant Synoptic Weather Processes and Interactions

Abstract

Every spring, biomass burning (BB) plumes from the Indochina Peninsula (ICP) are transported downstream by specific synoptic weather processes, potentially influencing regional weather through radiative effects of BB aerosols. However, the favorable weather patterns for transport toward inland China and how they interact with BB aerosols are not fully understood. In this study, we identified three predominant synoptic weather processes associated with evident BB plume transport toward southern China over the past 20 years. The first two—the low pressure over the continent and the cold frontal passage—account for more than 76% of all the events. In low-pressure events accompanied by surface warming, a cyclonic system hovers over southern China, with southerly winds favoring the northward movement of BB plumes throughout the lower troposphere. The second type is caused by a frontal passage lasting only 1–2 days, which lifts BB plumes to above 700 hPa and transports them downstream. To further explore aerosol feedback on different weather patterns, we conducted WRF-Chem simulations and found an average of 2°C cooling near the surface, along with 1.5°C warming in the lower troposphere over the southern coast of East Asia. Consequently, the more stable atmosphere suppresses the low-pressure system but enhances the cold frontal system. Meanwhile, anomalous circulations from aerosol radiative effects align with those during the frontal passage, boosting plume transport with a 45% (20%) rise in CO (BC) along the transport belt toward inland southern China. This work highlights the importance of considering the interactions between wildfire pollutants and different weather processes.