Modelling of multiphase chemical processes

Detailed process models that can be used for sensitivity studies as well as for interpretation of laboratory and field data are necessary to understand multiphase processes. A main objective here is the development of aerosol and cloud modules that combine complex multiphase chemistry with a detailed description of microphysical processes, and their application in three-dimensional atmospheric models

The simulations of multiphase chemistry processes consider size-resolution and different particle compositions. Droplet activation, phase transitions between gas and particle phases, and a large number of heterogeneous reactions within the droplet and on the particle surface are explicitly described. These computations require consideration of non-ideal solutions. In addition to the liquid phase, the focus is increasingly on the ice phase.

In the research area multiphase chemistry modeling,detailed aqueous phase mechanisms are developed and applied within numerical models studying the physico-chemical multiphase processing in cloud droplets and deliquescent aerosol particles. The main focus of the model applications is given to the analysis of aqueous phase oxidations und their effect on the tropospheric oxidation capacity. For modelling of the complex tropospheric multiphase system, a spectral 0-dimensional box model as well as the detailed air parcel model SPACCIM (SPectral Aerosol Cloud Chemistry Interaction Model; Wolke et al., 2005) which were developed within the modelling department can be used. The currently applied multiphase mechanism consists of a extended RACM-MIM2 gas phase mechanism (Karl et al., 2006; Tilgner et al., 2008) with about 281 Reactions and the aqueous phase mechanism CAPRAM (Chemical Aqueous Phase Radical Mechanism) with up to 777 reactions in the newest version CAPRAM 3.0 (Herrmann et al., 2005). The phase transfer of currently 52 soluble species is treated in the models after the approach by Schwartz (1986; In: Jaeschke, W. (Ed.), Chemistry of Multiphase Atmospheric Systems, NATO ASI Series, Springer, Berlin, pp. 415-471).