For many years aerosol particles have been recognised for their potentially negative impact on human health and ecosystems. This has lead to regulatory legislation regarding emissions and concentration levels of particulate matter all over the world. More recently it was also acknowledged that particles play an important role in the global climate by their influence on Earth's radiative balance.
Emissions, gas-particle interactions, aerosol dynamics, cloud processing, transport and deposition influence the evolution and fate of aerosol particles. These processes cannot be constrained by measurements alone. Modelling plays a key role for quantitatively integrating knowledge and for evaluating our understanding of physical and chemical processes in the atmosphere.
The main goal of aerosol modelling is to establish a detailed description of the aerosol particle concentrations and their composition and size distribution. This requires advanced modelling techniques and innovation as well as reliable validation data of particle characteristics.
Aerosol models may also provide a predictive capability for future projections of the outcome of policy strategies on emissions. Consequently, we need aerosol models that properly describe the cycle of formation, dispersion and removal of particles. Such validated models can be used as cost-effective tools for reliable studies of the current status and predictions for various environmental and health impacts in the future.
Method and aerosol modules
The aerosol modules to be implemented in a ATCM (Atmospheric Transport and Chemistry Model), such as MATCH (Multiple-Scale Atmospheric Transport and Chemistry Model) generally take into account gas-to-particle conversion and aerosol dynamics and enable simulation of the complete aerosol number/mass/composition distribution, including the aerosol components' state of mixture (internal/external).
The soluble material particles (sulphate, nitrate, ammonium and sodium chloride) and the insoluble material particles (organic carbon, elemental carbon and crustal elements) are classified as tracers with different size ranges, including nucleation, Aitken, accumulation and coarse modes. The particles grow by coagulation and condensation inside the modes and depending on their size can subsequently be moved to larger modes.
The importance of the aqueous phase is addressed in terms of particle production, scavenging and cycling through clouds. Special attention is given to the link between dry deposition and micrometeorology/turbulence schemes.