Elsevier

Urban Climate

Volume 10, Part 4, December 2014, Pages 720-731
Urban Climate

Modeling the multiphase processing of an urban and a rural air mass with COSMO–MUSCAT

https://doi.org/10.1016/j.uclim.2014.02.001Get rights and content
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Highlights

  • Detailed aqueous phase chemistry (CAPRAM 3.0i) was used in COSMO–MUSCAT.

  • Comparison between CAPRAM 3.0i and a simple inorganic mechanism.

  • Cloud chemistry has effects on HOx-budget and pH.

  • Fate of dicarboxyilc acids was investigated.

Abstract

A reduced version of the complex aqueous phase mechanism CAPRAM3.0i (C3.0RED) was used in the regional chemistry transport model COSMO–MUSCAT in a 2-D application. Besides sulfate and nitrate production, the mechanism treats a complex HOx-chemistry, transition metal ion chemistry and organic species up to C4. The effects of the cloud chemistry on the chemical composition of air and particles were investigated. Sensitivity studies were conducted for an urban and a rural air mass. For this purpose simulations with C3.0RED were compared to ones with a simple inorganic aqueous phase mechanism (INORG) and without aqueous phase chemistry. A reduction of the gas phase concentrations of major oxidants was observed especially in the urban environment. Compared to INORG, C3.0RED is always more acidic leading to shifts in several chemical subsystems, (e.g. production of sulfate). Using C3.0RED instead of INORG, differences in sulfate mass of 3% to −15% occurred. The modeled O/C-ratio tends to be higher than observations as C3.0RED does not consider the whole population of organics and no insoluble organic mass. Nevertheless, the modeled concentration of glyoxalic acid is in the range of atmospheric measurements in both environments, whereas oxalic acid and pyruvic acid are underestimated in the urban case.

Abbreviations

C3.0RED
reduced version of CAPRAM
CAPRAM
chemical aqueous phase radical mechanism
CCN
cloud condensation nuclei
COSMO Model
model of consortium for small-scale modeling
CTM
chemistry transport model
INORG
inorganic mechanism
MUSCAT Model
multiscale chemistry aerosol transport model
RACM-MIM2ext
regional atmospheric chemistry mechanism with Mainz isoprene modul and organic extension
TMI
transition metal ion

Keywords

Multiphase cloud chemistry
CAPRAM
Regional modeling
MUSCAT
Chemistry transport model
Urban environment

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