Towards integrated modelling of atmospheric composition: approach of the SILAM system.

M.Sofiev, J.Vira, M.Prank, J.Soares, R.Kouznetsov, P.Siljamo, J.Kukkonen

The paper presents the new generation of the System for Integrated modeLling of Atmospheric coMposition SILAM. The new v.5 of the system includes 5 transformation modules: CMB-based gas-phase, original scheme for heterogeneous transformations, linearised scheme for sulphur oxides, generalised degradation of an abstract tracer, and radioactive decay. Two original transformation schemes for aerosols - the equilibrium-based and the basic aerosol dynamics - are connected with the sectional and modal representations of particle size spectrum and with chemical transformation routines. The list of source terms includes point and area emission source types for anthropogenic inventories, nuclear bomb explosion, as well as the emission sub-models for biogenic VOC, allergenic pollen, sea salt.

The model includes two sub-systems for the data assimilation: 3D- and 4D-VAR, which allow the system initialization from the observations, dynamic adjustment of the computations to the available data, and enable identification or adjustment of source characteristics. The adjoints to the system transport and some chemical modules can be used for analysis of the observational results.

The meteorological pre-processor and transport modules allow for the application scales ranging from global down to beta-meso scale with spatial resolution varying from degrees up to 1 km.

The system is being evaluated against available chemical and aerosol observations in Europe and over the globe and is used for operational forecasting of air quality in several on-going projects.