Aerosol process modelling
In aerosol chamber and laboratory studies often a large number of nonlinearly coupled subprocesses have to be considered simultaneously, making it difficult if not impossible to analyse the measured data directly. Therefore the gain of information is often largely improved by supplementing the experiments with numerical simulations employing detailed physical and chemical process models. At IMK-AAF the COSIMA suite of aerosol behaviour codes and data analysis tools has been developed for this purpose. Furthermore the codes are applied to support the design of experiments and to extrapolate the results of chamber or laboratory studies to atmospheric conditions. In addition the codes can also be used to simulate the aerosol behaviour in technical facilities.
The process models of IMK-AAF are aiming at a detailed theoretical understanding and numerical simulation of aerosol dynamics, thermodynamics, heterogeneous and homogeneous chemistry, composition and optical properties of complex aerosol systems under tropospheric and stratospheric conditions. Therefore, the model development is accompanied by independent theoretical work and dedicated experimental studies. Major research tasks are:
- Formation and behaviour of pure secondary organic aerosol (SOA) and of coated particles
- Transport, uptake kinetics and heterogeneous chemistry of trace gases
- Simulation of systems with irregularly formed agglomerate particles, e.g. soot or technical aerosols, employing fractal scaling laws
- Influence of aerosol ageing on climatically relevant properties
- Effect of particle structure, composition and mixing state on aerosol optics
Based on these developments, we plan to devise efficient aerosol process modules, potentially in reduced or parameterised form, for implementation into comprehensive regional scale models. In this context the detailed models also provide a reference for testing and validation of simplified approaches or parameterisations.
Aerosol simulation - COSIMA web interface
In July 2013 a web based version of the detailed numerical aerosol model COSIMA-F has been made freely available to the scientific community. This code describes the structural properties and dynamical evolution of ramified, apparently irregularly shaped agglomerates or aggregates, e.g. from combustion or plasma processes, based on statistical mechanics and fractal scaling laws. However, it can also be operated like a conventional aerosol behaviour code when dealing with compact particles. Several entirely editable default scenarios are available. COSIMA-F has been extensively validated against experimental results obtained in the AIDA and NAUA chambers of IMK-AAF. For more information regarding this ongoing project or conducting your own simulations please visit the COSIMA homepage.