Clouds are a mixture of gases, particles and hydrometeors (aqueous cloud droplets or solid ice particles), which are not at all chemically inert. In particular, in/on cloud droplets a great variety of chemical processes can take place. Those chemical multiphase processes and interactions in clouds and fog can substantially modify the chemical composition and thus the physical properties of both tropospheric aerosols and the surrounding gas phase on all scales up to the global scale. To quantify the environmental relevance and consider the effects of theses chemical and physical cloud interactions in future coupled chemistry-transport-models, detailed and combined laboratory, field and model studies are essential. Particularly, process models are an adequate tool to investigate chemical in-cloud processes in detail by means of complex multiphase chemical mechanisms. For that reason, complex multiphase mechanisms (e.g., MCM-CAPRAM) and detailed multiphase model frameworks (SPACCIM, COSMO-MUSCAT) are developed and applied at TROPOS in close cooperation between the chemistry and modelling department. The thematic emphasis of the mechanism and model development, and the accompanying model studies are especially placed on
• a better understanding of the formation mechanisms of secondary aerosol constituents and of aerosol-cloud-interaction processes
• the characterisation of cloud effects on the composition of the tropospheric gas phase
• the characterisation of the cloud effects on the tropospheric multiphase oxidation budget and the residence time of important trace compounds in the troposphere
• the development of condensed mechanisms for regional scale chemistry-transport models (COSMO-MUSCAT)
• the implementation of cloud chemistry representations in coupled chemistry-transport-models and
• the interpretation of measurements from cloud field experiments such as FEBUKO and HCCT-2010.
In the research area multiphase modelling at TROPOS, the scientific work is focused on the further development of the aqueous phase mechanism CAPRAM and its application in the multiphase model SPACCIM as well as the application of reduced CAPRAM versions in a regional scale chemistry-transport-model (COSMO-MUSCAT). Detailed information and corresponding references to the above-mentioned chemical mechanisms and models can be found on the related links given below.