Abstract
Abstract. Sulfur dioxide (SO2) is a major atmospheric pollutant and precursor of sulfate aerosols, which influences air quality, cloud microphysics, and climate. Therefore, better understanding the conversion of SO2 to sulfate is essential to simulate and predict sulfur compounds more accurately. This study evaluates the effects of in-cloud aqueous-phase chemistry on SO2 oxidation in the Community Earth System Model version 2 (CESM2). We replaced the default parameterized SO2 aqueous-phase reactions with detailed HOx, Fe, N, and carbonate chemistry in cloud droplets and performed a global simulation for 2014–2015. Compared with the observations, the results incorporating detailed cloud aqueous-phase chemistry greatly reduced SO2 overestimation. This overestimation was reduced by 0.1–10 ppbv (parts per billion by volume) in most of Europe, North America, and Asia and more than 10 ppbv in parts of China. The biases in annual simulated SO2 mixing ratios decreased by 46 %, 41 %, and 22 % in Europe, the USA, and China, respectively. Fe chemistry and HOx chemistry contributed more to SO2 oxidation than N chemistry. Higher concentrations of soluble Fe and higher pH values could further enhance the oxidation capacity. This study emphasizes the importance of detailed in-cloud aqueous-phase chemistry for the oxidation of SO2. These mechanisms can improve SO2 simulation in CESM2 and deepen understanding of SO2 oxidation and sulfate formation.
Highlights
Sulfur dioxide (SO2) is one of the major atmospheric pollutants
To improve the global simulation of SO2 in this study, we used Community Earth System Model 2 (CESM2) to evaluate the effects of detailed in-cloud aqueous-phase reaction mechanisms on the capacity for SO2 oxidation
Most them are in the range of 0.1– 10 ppbv, and some can be greater than 10 ppbv in some regions of CN
Summary
Sulfur dioxide (SO2) is one of the major atmospheric pollutants. Sulfate can be regarded as one of the core species in the atmosphere. It is one of the major components of fine particles (PM2.5) which cause haze pollution and affect human health, especially in East and South Asia (Buchard et al, 2014; Chen et al, 2018; Quan et al, 2015; Geng et al, 2019). Sulfate itself is one of the key species affecting radiative forcing, which directly influences climate change Only through a better understanding of SO2, especially the process of its oxidation to sulfate, can we better understand sulfate and explore all the issues above (Hung et al, 2018)
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