A model for cloud chemistry: A comparison between model simulations and observations in stratus and cumulus

Important Role of Low Cloud and Fog in Sulfate Aerosol Formation During Winter Haze Over the North China Plain

“…The traditional sulfate formation mechanisms include the gas‐phase oxidation of SO 2 by the hydroxyl radical (OH) and the aqueous‐phase oxidation of S(IV) (=SO 2 · H 2 O + HSO 3 − + SO 3 2− ) by ozone (O 3 ), hydrogen peroxide (H 2 O 2 ), nitrogen dioxide, organic peroxides, and O 2 catalyzed by transition metal ions (TMI) in cloud/fog droplets (Calvert et al., 1978; T. Liu et al., 2021; Pandis & Seinfeld, 2016). In part, it is thought that the most important pathway for sulfate formation in the troposphere is the oxidation of SO 2 by H 2 O 2 or O 3 in clouds (Chin et al., 1996; Liang & Jacobson, 1999; Qin et al., 2015; Restad et al., 1998), supported by many aerial surveys and topographic cloud experiments (Benedict et al., 2012; de Valk, 1994; B. Ervens et al., 2018; Harris et al., 2014; Hegg & Hobbs, 1981; Sorooshian et al., 2007; Wonaschuetz et al., 2012). However, many studies proposed that global/regional atmospheric chemical transport models including traditional sulfate formation mechanisms tend to greatly underestimate sulfate concentrations in highly polluted regions like the North China Plain (NCP), China (Cheng et al., 2016), where mass concentrations of sulfate can reach 20–60 μg m −3 and even more than 100 μg m −3 during severe winter haze events, accounting for 10%–26% of fine particulate matter (PM 2.5 ) (Guo et al., 2014; Han et al., 2016; Y. Liu et al., 2019; Z. Liu et al., 2016; Sun et al., 2016).…”

“…The traditional sulfate formation mechanisms include the gas-phase oxidation of SO 2 by the hydroxyl radical (OH) and the aqueous-phase oxidation of S(IV) (=SO 2 • H 2 O + HSO 3 + SO 3 2 ) by ozone (O 3 ), hydrogen peroxide (H 2 O 2 ), nitrogen dioxide, organic peroxides, and O 2 catalyzed by transition metal ions (TMI) in cloud/fog droplets (Calvert et al, 1978;Pandis & Seinfeld, 2016). In part, it is thought that the most important pathway for sulfate formation in the troposphere is the oxidation of SO 2 by H 2 O 2 or O 3 in clouds (Chin et al, 1996;Liang & Jacobson, 1999;Qin et al, 2015;Restad et al, 1998), supported by many aerial surveys and topographic cloud experiments (Benedict et al, 2012;de Valk, 1994;B. Ervens et al, 2018;Harris et al, 2014;Hegg & Hobbs, 1981;Sorooshian et al, 2007;Wonaschuetz et al, 2012).…”