The effect of mass transfer parameterization and ice retention on the scavenging and redistribution of SO₂ by a deep...

A chemistry module with the aqueous chemistry coupled with the complex 3D nonhydrostatic atmospheric model is used to investigate how the representation of gas-aqueous mass transfer and ice retention affect the SO₂ redistribution in the presence of a convective cloud. Gas uptake to the liquid water is calculated using both Henry's law equilibrium (HE) and kinetic mass transport (KMT). The constant retention coefficients for SO₂ (k _ret = 0.46) and for H₂O₂ (k _ret = 0.64) are used. It is shown that the amount of SO₂ in the air at higher altitudes (10-12 km) is greater when partial retention (PR) is included. All values of k _ret between 0 and 1 represented the partial retention (PR), while complete retention (CR) means the entire mass of the gas from the solution remained in the ice phase (k _ret = 1). Total mass of SO₂ in the air in the entire domain was greater in the case of PR than in the case when the CR was assumed (at the end of the integration time, 0.11% for HE and 0.61% for KMT) and in KMT than in the HE case (0.9% for CR and 1.4% for PR). The amount of SO₂ in the ice phase was lower in the case of PR for both HE and KMT. The highest concentrations of S(IV) in rainwater were in the case of HE-CR, while the smallest values were in the case of KMT-PR. Total precipitation of S(IV) in PR exhibits 90% relative to CR, if HE was assumed. When KMT was used, PR gives 81.7% S(IV) relative to CR. Scavenging was the highest in the HE-CR case and the lowest in the KMT-PR case. If HE is assumed, averaged cumulative mass (ACM) of S(IV) precipitation per unit of domain surface for the CR case was 11.1% greater than in the PR case (if KMT was assumed, this difference was greater, 22.4%). Similarly, ACM for HE is 24.1% greater than KMT for the CR case and 36.8% for the PR case.