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Performance of the EMEP Unified Model for Ozone

This study evaluates the performance of the EMEP Unified Model for ozone against observational data from EMEP stations and CITY DELTA stations. The model shows high correlation coefficients for daily mean and daily max ozone values, but struggles to accurately reproduce nighttime NO2 levels. The model tends to underestimate high ozone values and exceedance days. Overall, the model performs well but has limitations in Mediterranean regions.

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Performance of the EMEP Unified Model for Ozone

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  1. Title Performance of theEMEP Unified model for Ozone Leonor Tarrasón On behalf of Jan Eiof Jonson and David Simpson TFMM - Valencia 9-11 April 2003

  2. EMEP Unified Model I Horizontal resolution: Regional 50 x 50 km2 (170 x 133 cells, centered over Europe) Vertical resolution:20η-layers (up to 100 hPa), 10 layers in PBL Off-line meteorology:3-h meteorological input from HIRLAM Boundary conditions:Flexible choice (modeled from Oslo CTM2, TM3 or climatological Logan data for O3). Currently climatological BCs are used. Emissions: EMEP emissions estimates for SOx, NOx,NH3, VOC,CO PM2.5 and PM10 from TNO-CEPMEIP project Meteorologisk Instituttmet.no

  3. EMEP Unified Model II Chemistry:TWO STEP chemical solver and flexible system where any chemistry can be processed (GENCHEM). UNI - OZONEEMEP photochemistry(69 species, 170 reactions) UNI - ACIDEMEP acidification chemistry(10 components) UNI - AEROEMEP acid. chem., EQSAM equilibrium chem. Multimono aerosol dynamics (14 species, 4 modes) Dry Deposition:Resistance analogy, stomatal uptake for all gases, including O3, size dependent for PM Wet Deposition:EMEP scavenging ratios, precipitation dependent for PM is size and solubility dependent Advection:4th order Bott scheme horizontally (2nd order vertically) Flexible time step control Meteorologisk Instituttmet.no

  4. Schematic structure of EMEP UNIFIED Boundary, lateral and initial conditions Meteorological conditions Advection (Bott scheme) Emissions SOA module UNI - AERO EMEP acidification 14 species, 4 size modes UNI - ACID EMEP acidification 10 species + PPM UNI - OZONE EMEP photochemistry 69 species, 170 reactions Aerosol dynamics Multimono PPM mass: 2 species Dry and Wet Deposition

  5. Main developments in UNI-OZONE since July 2002 • Dry deposition routines1)The model version in EMEP BC used a bulk approach. • 2) Introduction of the effect of NH3 in SO2 surface resistance • Emission routines • 1) New description of height of emission by sector (specially for power combustion and industrial sources). • 2) New gridded data for PM10 and PM2.5 from TNO/CEPMEIP • Wet deposition routines • 1) Heterogeneous sulphur chemistry explicitly introduced • Chemistry • 1) Introduction of oxidant limitation in sulphur chemistry • 2) Introduction of coarse nitrate Meteorologisk Instituttmet.no

  6. O3 daily maxTimeseries 1995 2000 Meteorologisk Instituttmet.no

  7. Max O3 – All EMEP stationsUnified EMEP model performance Meteorologisk Instituttmet.no

  8. O3 daily max timeseries Meteorologisk Instituttmet.no

  9. Bias=-15%, r=0.65 Bias=-15%, r=0.59 Max O3 – Mediterranean EMEP stations Meteorologisk Instituttmet.no

  10. O3 daily maxSelection of stations active since 1990 (18) Meteorologisk Instituttmet.no

  11. O3 daily meanUnified EMEP model performance Meteorologisk Instituttmet.no

  12. O3 daily meanTimeseries year 2000 Meteorologisk Instituttmet.no

  13. 1990 Bias=-30%, r=0.73 2000 Bias=-18%, r=0.50 NO2 – All EMEP stations Meteorologisk Instituttmet.no

  14. NO2 correlation coefficient in city areasCITY DELTA model intercomparison1999 Paris, day Paris, nigth Milan, night Milan,day (EMEP Unified in orange) Meteorologisk Instituttmet.no

  15. Bias in city areasCITY DELTA Milan, bias O3(EMEP model in Orange) Milan, bias NO2 Meteorologisk Instituttmet.no

  16. Correlation coefficient for O3CITY DELTA London (EMEP model in Orange) Milan Meteorologisk Instituttmet.no

  17. Conclusions on EMEP model O3 performance • The UNIFIED EMEP model performance has studied in comparison with EMEP stations for 1990,1995 and 2000 and in CITY DELTA stations for 1999. • Correlation coefficients in regional scale are high, between 0.6 and 0.8 for daily mean ozone and daily max values. The summer mean ozone bias is below 10%. • For NO2, correlation coefficients at regional scale vary between 0.5 and 0.7 but the model has difficulties to reproduce at night time NO2. • At Mediterranean stations, model performance is poorer than in average for the rest of Europe, as expected given the limitations of transport representation in Mediterranean regions. • Frequency distributions show that the model tends to underestimate high ozone values. This is also the conclusion from the comparison of observed days with exceedance over 60ppb: the model tends to underestimate exceedance days. • Note that the underestimation of high ozone values is more pronounced at the end of the 1990s  consistent with the general trend of increase of ozone mean values Meteorologisk Instituttmet.no

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