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- Title
Important Role of Low Cloud and Fog in Sulfate Aerosol Formation During Winter Haze Over the North China Plain.
- Authors
Cai, Suyi; Liu, Tengyu; Huang, Xin; Song, Yu; Wang, Tiantian; Sun, Zhaobin; Gao, Jian; Ding, Aijun
- Abstract
Sulfate aerosol greatly contributes to wintertime haze pollution in emission‐intensive regions like the North China Plain (NCP) in China. Fast sulfate increase and accumulation are usually recorded during winter haze; however, the multiphase oxidation of sulfur dioxide (SO2) and the physical processes affecting near‐surface sulfate are not fully understood. By combining in situ observations and numerical simulations, we found that high sulfur oxidation ratios (>0.6) under heavily polluted conditions are associated with low clouds and fog over NCP, induced by the moist southerly airflow. Thick low clouds and high SO2 levels in NCP provide a reaction environment for sulfate production. The sulfate production rate in cloud water can reach 0.5–1.3 μg m−3 h−1. The results demonstrate that the vertical mixing of sulfate generated within the cloud water to the surface plays a significant role in rapid sulfate production, highlighting the importance of understanding cloud‐water processes in haze pollution. Plain Language Summary: Sulfate has been recognized as an important chemical component of atmospheric aerosols, especially during winter haze events. Rapid increases in sulfate concentrations are frequently observed during heavy pollution in the North China Plain (NCP) of China. However, the processes involved in the multiphase oxidation of sulfur dioxide (SO2) and the physical processes influencing sulfate variations near the surface remain unclear. In particular, the contribution of traditional in‐cloud sulfate production to the surface sulfate has been considered to be negligible in the NCP. Here, we revisited the role of in‐cloud sulfate production in the NCP by using ground‐based observations, radiosonde measurements, and model simulation. Our results indicate that the rapid conversion of SO2 to sulfates during heavy pollution is associated with the presence of low clouds and fog. We find that high sulfate production rates in cloud water lead to the rapid accumulation of sulfate, which is vertically mixed to the surface, resulting in a rapid increase in surface sulfate concentrations. This work sheds a new perspective on understanding the role of sulfate production in cloud water and its impact on air pollution. Key Points: High sulfur oxidation ratios under heavy pollution conditions in the North China Plain are associated with low clouds and fog formationSulfate production rates within cloud water can reach 0.5–1.3 μg m−3 h−1, with NO2 and O3 oxidation pathways dominatingVertical mixing of sulfate produced in cloud water to the surface causes a rapid increase in near‐surface sulfate concentration
- Subjects
CHINA; SULFATE aerosols; FOG; ATMOSPHERIC aerosols; HAZE; SULFUR cycle; AIR pollution; SULFATE pulping process
- Publication
Geophysical Research Letters, 2024, Vol 51, Issue 3, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2023GL106597