Towards an online-coupled chemistry-climate model: evaluation of trace gases and aerosols in COSMO-ART

摘要

The online-coupled, regional chemistry transport model COSMO-ART is evaluatedfor periods in all seasons against several measurement datasets to assess itsability to represent gaseous pollutants and ambient aerosol characteristicsover the European domain. Measurements used in the comparison includelong-term station observations, satellite and ground-based remote sensingproducts, and complex datasets of aerosol chemical composition and numbersize distribution from recent field campaigns. This is the first time thesecomprehensive measurements of aerosol characteristics in Europe are used toevaluate a regional chemistry transport model. We show a detailed analysis ofthe simulated size-resolved chemical composition under differentmeteorological conditions. Mean, variability and spatial distribution of theconcentrations of O₃ and NO_x are well reproduced. SO₂is found to be overestimated, simulated PM_2.5 and PM₁₀levels are on average underestimated, as is AOD. We find indications of anoverestimation of shipping emissions. Time evolution of aerosol chemicalcomposition is captured, although some biases are found in relativecomposition. Nitrate aerosol components are on averageoverestimated, and sulfates underestimated. The accuracy of simulatedorganics depends strongly on season and location. While stronglyunderestimated during summer, organic mass is comparable in spring andautumn. We see indications for an overestimated fractional contribution ofprimary organic matter in urban areas and an underestimation of SOA at manylocations. Aerosol number concentrations compare well with measurements forlarger size ranges, but overestimations of particle number concentration withfactors of 2–5 are found for particles smaller than 50 nm. Sizedistribution characteristics are often close to measurements, but showdiscrepancies at polluted sites. Suggestions for further improvement of themodeling system consist of the inclusion of a revised secondary organicaerosols scheme, aqueous-phase chemistry and improved aerosol boundaryconditions. Our work sets the basis for subsequent studies of aerosolcharacteristics and climate impacts with COSMO-ART, and highlights areaswhere improvements are necessary for current regional modeling systems ingeneral.