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The European emission Adaptation SYstem for the WRF-Chem model (EASYWRF-Chem) has been developed to generate chemical information supporting the WRF-Chem requirements from any emission inventory based on the CORINAIR methodology. Using RADM2 and RACM2 mechanisms, “emission species” are converted into “model species” thanks to the SAPRC methodology for gas phase pollutant and the PM 10 and PM 2.5 fractions. Furthermore, by adapting US EPA PM 2.5 profiles, the processing of aerosol chemical speciation profiles separates the unspeciated PM 2.5 emission into five chemical families: sulfates, nitrates, elemental carbon, organic aerosol and unspeciated aerosol. The evaluation of the model has been performed by separately comparing model outcomes with (i) meteorological measurements; (ii) NO 2 , O 3 , PM 10 and PM 2.5 mass concentrations from the regional air quality monitoring network; (iii) hourly-resolved data from four field campaign measurements, in winter and in summer, on two sites in the French northern region. In the latter, a High Resolution — Time of Flight — Aerosol Mass Spectrometer (HR-ToF-AMS) provided non-refractory PM 1 concentrations of sulfate, nitrate and ammonium ions as well as organic matter (OM), while an aethalometer provided black carbon (BC) concentrations in the PM 2.5 fraction. Meteorological data (temperature, wind, relative humidity) are well simulated for all the time series data except for specific events as wind direction changes or rainfall. For particulate matter, results are presented by considering firstly the total mass concentration of PM 2.5 and PM 10 . EASYWRF-Chem simulations overestimated the PM 10 mass concentrations by + 22% and + 4% for summer and winter periods respectively, whereas for the finer PM 2.5 fraction, mass concentrations were overestimated by + 20% in summer and underestimated by − 13% in winter. Simulated sulfate concentrations were underestimated and nitrate concentrations were overestimated but hourly variations were well represented. Ammonium particulate matter was well simulated for all seasons. Although simulated particulate OM concentrations in PM 2.5 were underestimated, their hourly variations were well reproduced by the model. At least BC measurements revealed that EASYWRF-Chem forecast performance was higher in winter than during summer when BC concentrations were very low.

This paper reports on the first application of a Nord-Pas-de-Calais regional emission inventory to the CHIMERE-MM5 modelling system. Using statistical indexes, we compare computed data to hourly observations and daily maximum of ozone and PM concentration measured with the monitoring station network data period in order to evaluate the performance of the modelling system for the selected area. This comparison is presented for a coastal location (Dunkerque: 51.03° N/2.37° E) and an inland location (Lille: 50.63° N/3.07° E) during the June July summer 2006 period. The model gives an excellent reproduction of the daily ozone cycle both for inland and coastal region but underestimates (20 μg/m3 on average) the O3 hourly maxima over 180 μg/m3. The model underestimates the PM10 measured concentration and has difficulties to reproduce hourly maxima over 60 μg/m3 for both inland and coastal stations. The system has difficulties to reproduce O3 concentration when air masses flows are continental. The poor representation of monitoring coastal station for particles makes the system validation more delicate for this area. We recommend using high resolution (3 km) and grid nudging for the production meteorological data for the coastal location due to specific local dynamical conditions.