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@ARTICLE{Huijnen:9367,
      author       = {Huijnen, V. and Eskes, H.J. and Poupkou, A. and Elbern, H.
                      and Boersma, K.F. and Foret, G. and Sofiev, M. and
                      Valdebenito, A. and Flemming, J. and Stein, O. and Gross, A.
                      and Robertson, L. and D'Isidoro, M. and Kioutsioukis, I. and
                      Friese, E. and Amstrup, B. and Berstrom, R. and Strunk, A.
                      and Vira, J. and Zyryanov, D. and Maurizi, A. and Melas, D.
                      and Peuch, V.-H. and Zerefos, C.},
      title        = {{C}omparison of {OMI} {NO}2 tropospheric columns with an
                      ensemble of global and {E}uropean regional air quality
                      models},
      journal      = {Atmospheric chemistry and physics},
      volume       = {10},
      issn         = {1680-7316},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {PreJuSER-9367},
      pages        = {3273 - 3296},
      year         = {2010},
      note         = {GEMS was funded by the European Commission under the EU
                      Sixth Research Framework Programme, contract number
                      SIP4-CT-2004-516099. The authors would like to thank two
                      anonymous reviewers for the constructive comments that led
                      to a substantial strengthening of the content of the paper.},
      abstract     = {We present a comparison of tropospheric NO2 from OMI
                      measurements to the median of an ensemble of Regional Air
                      Quality (RAQ) models, and an intercomparison of the
                      contributing RAQ models and two global models for the period
                      July 2008 - June 2009 over Europe. The model forecasts were
                      produced routinely on a daily basis in the context of the
                      European GEMS ("Global and regional Earth-system
                      (atmosphere) Monitoring using Satellite and in-situ data")
                      project. The tropospheric vertical column of the RAQ
                      ensemble median shows a spatial distribution which agrees
                      well with the OMI NO2 observations, with a correlation
                      r=0.8. This is higher than the correlations from any one of
                      the individual RAQ models, which supports the use of a model
                      ensemble approach for regional air pollution forecasting.
                      The global models show high correlations compared to OMI,
                      but with significantly less spatial detail, due to their
                      coarser resolution. Deviations in the tropospheric NO2
                      columns of individual RAQ models from the mean were in the
                      range of $20-34\%$ in winter and $40-62\%$ in summer,
                      suggesting that the RAQ ensemble prediction is relatively
                      more uncertain in the summer months.The ensemble median
                      shows a stronger seasonal cycle of NO2 columns than OMI, and
                      the ensemble is on average $50\%$ below the OMI observations
                      in summer, whereas in winter the bias is small. On the other
                      hand the ensemble median shows a somewhat weaker seasonal
                      cycle than NO2 surface observations from the Dutch Air
                      Quality Network, and on average a negative bias of
                      $14\%.Full$ profile information was available for two RAQ
                      models and for the global models. For these models the
                      retrieval averaging kernel was applied. Minor differences
                      are found for area-averaged model columns with and without
                      applying the kernel, which shows that the impact of
                      replacing the a priori profiles by the RAQ model profiles is
                      on average small. However, the contrast between major
                      hotspots and rural areas is stronger for the direct modeled
                      vertical columns than the columns where the averaging
                      kernels are applied, related to a larger relative
                      contribution of the free troposphere and the coarse
                      horizontal resolution in the a priori profiles compared to
                      the RAQ models.In line with validation results reported in
                      the literature, summertime concentrations in the lowermost
                      boundary layer in the a priori profiles from the DOMINO
                      product are significantly larger than the RAQ model
                      concentrations and surface observations over the
                      Netherlands. This affects the profile shape, and contributes
                      to a high bias in OMI tropospheric columns over polluted
                      regions. The global models indicate that the upper
                      troposphere may contribute significantly to the total column
                      and it is important to account for this in comparisons with
                      RAQ models. A combination of upper troposphere model biases,
                      the a priori profile effects and DOMINO product retrieval
                      issues could explain the discrepancy observed between the
                      OMI observations and the ensemble median in summer.},
      keywords     = {J (WoSType)},
      cin          = {ICG-2},
      ddc          = {550},
      cid          = {I:(DE-Juel1)VDB791},
      pnm          = {Atmosphäre und Klima},
      pid          = {G:(DE-Juel1)FUEK406},
      shelfmark    = {Meteorology $\&$ Atmospheric Sciences},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000276663600009},
      url          = {https://juser.fz-juelich.de/record/9367},
}