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

Abstract

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.