Articles | Volume 18, issue 3
https://doi.org/10.5194/acp-18-2225-2018
https://doi.org/10.5194/acp-18-2225-2018
Research article
 | 
15 Feb 2018
Research article |  | 15 Feb 2018

Modeling the partitioning of organic chemical species in cloud phases with CLEPS (1.1)

Clémence Rose, Nadine Chaumerliac, Laurent Deguillaume, Hélène Perroux, Camille Mouchel-Vallon, Maud Leriche, Luc Patryl, and Patrick Armand

Abstract. The new detailed aqueous-phase mechanism Cloud Explicit Physico-chemical Scheme (CLEPS 1.0), which describes the oxidation of isoprene-derived water-soluble organic compounds, is coupled with a warm microphysical module simulating the activation of aerosol particles into cloud droplets. CLEPS 1.0 was then extended to CLEPS 1.1 to include the chemistry of the newly added dicarboxylic acids dissolved from the particulate phase. The resulting coupled model allows the prediction of the aqueous-phase concentrations of chemical compounds originating from particle scavenging, mass transfer from the gas-phase and in-cloud aqueous chemical reactivity. The aim of the present study was more particularly to investigate the effect of particle scavenging on cloud chemistry. Several simulations were performed to assess the influence of various parameters on model predictions and to interpret long-term measurements conducted at the top of Puy de Dôme (PUY, France) in marine air masses. Specific attention was paid to carboxylic acids, whose predicted concentrations are on average in the lower range of the observations, with the exception of formic acid, which is rather overestimated in the model. The different sensitivity runs highlight the fact that formic and acetic acids mainly originate from the gas phase and have highly variable aqueous-phase reactivity depending on the cloud acidity, whereas C3–C4 carboxylic acids mainly originate from the particulate phase and are supersaturated in the cloud.

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Short summary
A detailed aqueous phase mechanism CLEPS 1.1 is coupled with warm microphysics including activation of aerosol particles into cloud droplets. Simulated aqueous concentrations of carboxylic acids are close to the long-term measurements conducted at Puy de Dôme (France). Sensitivity tests show that formic and acetic acids mainly originate from the gas phase with highly variable aqueous-phase reactivity depending on cloud pH, while C3–C4 carboxylic acids mainly originate from the particulate phase.
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