Improvement of the representation of aerosols and aerosol-cloud interactions in the regional model COSMO and in ECHAM5

Aerosol particles undergo significant modifications during their residence time in the atmosphere. In particular, cloud processes have important effects on atmospheric aerosol concentrations, size distribution, chemical composition and mixing state. In a previous study it was estimated that on a global average an aerosol particle, sampled at a distance from a specific source, has been cycled three times through a cloud. This includes cycling through both stratiform and convective clouds. 

A similar configuration of aerosol physical processes (M7 aerosol module) and aerosol-cloud interactions (coupled double-moment cloud microphysics scheme) has been implemented in the regional climate model COSMO-CLM and the global climate model ECHAM5. The M7 aerosol module in the COSMO-CLM will be extended by an explicit and detailed treatment of cloud-borne particles following the approach developed by Hoose et al. (2008) for ECHAM5.

Different 2D simulations of orographic clouds will be conducted using the regional model COSMO-CLM. These process studies will help to improve the understanding of important microphysical processes and their effect on the aerosol population.

The global aerosol-climate model ECHAM5-HAM will be used to investigate the effects of the aerosol processing in clouds on a global scale.