An advanced scheme for wet scavenging and liquid-phase chemistry in a regional online-coupled chemistry transport model 1Laboratory for Air Pollution/Env. Technology, Empa Materials and Science, Duebendorf, Switzerland
01 Feb 2013
2C2SM Center for Climate Systems Modeling, ETH, Zurich, Switzerland
*now at: Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO, USA
Received: 12 August 2012 – Published in Atmos. Chem. Phys. Discuss.: 05 October 2012 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.
Revised: 25 January 2013 – Accepted: 29 January 2013 – Published: 01 February 2013
Citation: Knote, C. and Brunner, D.: An advanced scheme for wet scavenging and liquid-phase chemistry in a regional online-coupled chemistry transport model, Atmos. Chem. Phys., 13, 1177-1192, doi:10.5194/acp-13-1177-2013, 2013.