The EMEP MSC-W chemical transport model – technical description

Abstract

Abstract. The Meteorological Synthesizing Centre-West (MSC-W) of the European Monitoring and Evaluation Programme (EMEP) has been performing model calculations in support of the Convention on Long Range Transboundary Air Pollution (CLRTAP) for more than 30 years. The EMEP MSC-W chemical transport model is still one of the key tools within European air pollution policy assessments. Traditionally, the model has covered all of Europe with a resolution of about 50 km × 50 km, and extending vertically from ground level to the tropopause (100 hPa). The model has changed extensively over the last ten years, however, with flexible processing of chemical schemes, meteorological inputs, and with nesting capability: the code is now applied on scales ranging from local (ca. 5 km grid size) to global (with 1 degree resolution). The model is used to simulate photo-oxidants and both inorganic and organic aerosols. In 2008 the EMEP model was released for the first time as public domain code, along with all required input data for model runs for one year. The second release of the EMEP MSC-W model became available in mid 2011, and a new release is targeted for summer 2012. This publication is intended to document this third release of the EMEP MSC-W model. The model formulations are given, along with details of input data-sets which are used, and a brief background on some of the choices made in the formulation is presented. The model code itself is available at www.emep.int, along with the data required to run for a full year over Europe.

Air quality simulations for London using a coupled regional-to-local modelling system

“…The main EMEP MSC-W model has been widely used for both scientific studies and for policymaking in Europe, with references to evaluation and application studies available in Simpson et al (2012), Schulz et al (2013) and at http://www.emep.int (last access: 1 August 2018). EMEP4UK is described in Vieno et al (2010Vieno et al ( , 2014Vieno et al ( , 2016a; the version used here is based on EMEP MSC-W rv4.5.…”

“…Biogenic emissions of isoprenes and monoterpene are calculated at each time step according to insolation and surface temperature (Guenther et al, 1995). Emissions of wind-driven sea salt and NO x from soils are also calculated interactively as described by Simpson et al (2012), whereas lightning NO x emissions are prescribed. Import of Saharan dust is treated using a monthly dust climatology as a model boundary condition.…”

“…Sixteen land cover classes are used for dry deposition modelling and for the calculation of biogenic emissions. Ozone boundary conditions for the outer European domain are based on the approach in Simpson et al (2012), scaling a monthly climatology with clean air measurements at Mace Head. Initial and boundary conditions of all other species for the European domain are specified as fixed functions of latitude and time of year.…”

“…The gaseous chemical scheme used in EMEP4UK in this study is the CRI-v2-R5 mechanism (Watson et al, 2008), which has 220 species and 609 reactions. Five classes of fine and coarse particles, with differing size and deposition properties, are used in EMEP4UK along with the MARS (Model for an Aerosol Reacting System) equilibrium module for gas-aerosol partitioning of secondary inorganic aerosol (Binkowski and Shankar, 1995;Simpson et al, 2012) and a treatment of secondary organic aerosol formation using the volatility basis set approach Ots et al, 2016). Dry (including stomatal) and wet deposition of gases and particles are simulated.…”

“…Global and regional models use gridded emissions data to calculate transport and chemistry over global or regional modelling domains, such as EMEP MSC-W (EMEP, Simpson et al, 2012) used in this study, CAMx (Ramboll Environment and Health, 2016), CMAQ (Byun and Schere, 2006) and WRF-Chem (Grell et al, 2005). Models on a smaller scale apply detailed transport and fast chemistry processes to individual sources, such as ADMS-Urban (Owen et al, 2000) also used in this study, the US EPA model AER-MOD (Cimorelli et al, 2004) and CAR-FMI (Kukkonen et al, 2001).…”