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Aerosol and Cloud Modelling

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.

For further information please contact Dr. Karl-Heinz Naumann (retired)

 


Aerosol simulation 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.

 

 


Cloud modelling

At IMK-AAF numerous experiments on the nucleation efficiency of mineral dusts, soots, bioaerosols, and coated particles are conducted in the AIDA chamber and with single levitated droplets. Based on these experimental results parameterizations are developed for models on different scales in order to enhance our understanding of aerosol effects on the cloud ice phase. The goal of theses efforts is to gain insight regarding the aerosol influence on the development and intensity of precipitation and to reduce the uncertainty of the aerosol indirect effect on cold and mixed phase clouds in regional and global models. In this context, special emphasis is placed on the improvement of mid term climate projections. Research topics to be investigated:

  • Parameterisation development and cloud resolving modelling
  • Bioaerosol as ice nuclei and giant cloud condensation nuclei: Importance for the hydrological cycle and climate on the regional and global scale
  • Anthropogenic aerosol effects via mixed phase and ice clouds
  • Turbulence effects on cloud droplet activation
  • Detailled modelling of droplet activation and ice nucleation processes in the AIDA chamber

These activities are conducted within the Helmholtz-University Young Investigators group "Aerosol effects on Cloud Ice, Precipitation and Climate".

For further information please contact Prof. Corinna Hoose.