Abstract
Abstract. Clouds are reaction chambers for atmospheric trace gases and aerosols, and the associated precipitation is a major sink for atmospheric constituents. The regional chemistry-climate model COSMO-ART has been lacking a description of wet scavenging of gases and aqueous-phase chemistry. In this work we present a coupling of COSMO-ART with a wet scavenging and aqueous-phase chemistry scheme. The coupling is made consistent with the cloud microphysics scheme of the underlying meteorological model COSMO. While the choice of the aqueous-chemistry mechanism is flexible, the effects of a simple sulfur oxidation scheme are shown in the application of the coupled system in this work. We give details explaining the coupling and extensions made, then present results from idealized flow-over-hill experiments in a 2-D model setup and finally results from a full 3-D simulation. Comparison against measurement data shows that the scheme efficiently reduces SO2 trace gas concentrations by 0.3 ppbv (−30%) on average, while leaving O3 and NOx unchanged. PM10 aerosol mass was increased by 10% on average. While total PM2.5 changes only little, chemical composition is improved notably. Overestimations of nitrate aerosols are reduced by typically 0.5–1 μg m−3 (up to −2 μg m−3 in the Po Valley) while sulfate mass is increased by 1–1.5 μg m−3 on average (up to 2.5 μg m−3 in Eastern Europe). The effect of cloud processing of aerosols on its size distribution, i.e. a shift towards larger diameters, is observed. Compared against wet deposition measurements the system tends to underestimate the total wet deposited mass for the simulated case study.
Highlights
ART with a wet scavenging and aqueous-phase chemistry scheme
Numerical chemical transport models (CTMs) are used to of nitrate aerosols are reduced by typically 0.5–1 μg m−3 while sulfate mass is in- invaluable tools to improve our understanding of atmospheric creased by 1–1.5 μg m−3 on average
In this work we describe the coupling of the comprehensive wet scavenging and aqueous-phase chemistry scheme SCAV (Tost et al, 2006) with COSMO-ART
Summary
ART with a wet scavenging and aqueous-phase chemistry scheme. The coupling is made consistent with the cloud microphysics scheme of the underlying meteorological model cal reactions like the oxidatMionetohf osudlfsura(nHdegg and Hobbs, 1978; et al., W20a1lc0e; kEarnvdenTsaeytloarl,.,1D92a8061t)1a)orSwohyrigscahtneiccmocnostrmibpuotue nsdusb(sLtainm-. COSMO-ART (Vogel et al., 2009) is a recently developedSreogiloidnalECaTMrthwhich currently includes wet scavenging of aerosols but lacks a parametrization of aqueous-phase chemistry and wet deposition of gases. In this work we describe the coupling of the comprehensive wet scavenging and aqueous-phase chemistry scheme SCAV (Tost et al, 2006) with COSMO-ART. SCAV includes descriptions of the scavenging of both gases and aerosols, liquid-phase chemistry and a simple cloud processing of aerosols (in the sense of a mass transfer from smaller to larger particles). It had been originally developed for global models, making assumptions that are not reasonable for kilometer-scale regional modeling
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