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@ARTICLE{Zieger:20027,
      author       = {Zieger, P. and Weingartner, E. and Henzing, J. and Moerman,
                      M. and de Leeuw, G. and Mikkilä, J. and Ehn, M. and
                      Petäjä, T. and Clemer, K. and van Roozendael, M. and
                      Yilmaz, S. and Frieß, U. and Irie, H. and Wagner, T. and
                      Shaiganfar, R. and Beirle, S. and Apituley, A. and Wilson,
                      K. and Baltensperger, U.},
      title        = {{C}omparison of ambient aerosol extinction coefficients
                      obtained from in-situ, {MAX}-{DOAS} and {LIDAR} measurements
                      at {C}abauw},
      journal      = {Atmospheric chemistry and physics},
      volume       = {11},
      issn         = {1680-7316},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {PreJuSER-20027},
      pages        = {2603 - 2624},
      year         = {2011},
      note         = {We thank Jacques Warmer and the staff of KNMI at the CESAR
                      site for providing an excellent service during our campaign.
                      We thank the CINDI local organization team at KNMI, in
                      particular Ankie Piters, Mark Kroon, and Jennifer Hains, for
                      facilitating this very successful campaign. We gratefully
                      acknowledge Henk Klein-Baltink (KNMI) for providing the
                      ceilometer data. We also gratefully acknowledge the easy
                      access of the meteorological data used in this work via
                      http://www.cesar-observatory.nl. We thank Rahel Fierz (PSI)
                      for valuable discussions. Many thanks to Michel Tinquely
                      (PSI) for helping out with the COSMO data, which was
                      provided by the Swiss Federal Office of Meteorology and
                      Climatology (MeteoSwiss). NILU and especially Ann Mari
                      Fjaeraa are gratefully acknowledged for providing the air
                      mass trajectories. Many thanks to A. Rozanov from the
                      Institute of Environmental Physics, University of Bremen,
                      for providing the SCIATRAN radiative transfer model to
                      IUPHD. Hitoshi Irie thanks H. Takashima, Y. Kanaya, and
                      PREDE, Co., Ltd for their technical assistance in developing
                      and operating the MAX-DOAS instrument. Observation by
                      JAMSTEC was supported by the Japan EOS Promotion Program of
                      the Ministry of Education, Culture, Sports, Science and
                      Technology (MEXT), and by the Global Environment Research
                      Fund (S-7) of the Japanese Ministry of the Environment.
                      Katrijn Clemer (BIRA-IASB) was financially supported by the
                      AGACC project (contract SD/AT/10A) funded by the Belgian
                      Federal Science Policy Office. This work was financially
                      supported by the ESA Climate Change Initiative $Aerosol_cci$
                      (ESRIN/Contract No. 4000101545/10/I-AM) and by the
                      EC-projects Global Earth Observation and Monitoring (GEOmon,
                      contract 036677) and European Supersites for Atmospheric
                      Atmospheric Aerosol Research (EUSAAR, contract 026140).},
      abstract     = {In the field, aerosol in-situ measurements are often
                      performed under dry conditions (relative humidity RH <
                      $30-40\%).$ Since ambient aerosol particles experience
                      hygroscopic growth at enhanced RH, their microphysical and
                      optical properties - especially the aerosol light scattering
                      are also strongly dependent on RH. The knowledge of this RH
                      effect is of crucial importance for climate forcing
                      calculations or for the comparison of remote sensing with
                      in-situ measurements. Here, we will present results from a
                      four-month campaign which took place in summer 2009 in
                      Cabauw, The Netherlands. The aerosol scattering coefficient
                      sigma(sp)(lambda) was measured dry and at various,
                      predefined RH conditions between 20 and $95\%$ with a
                      humidified nephelometer. The scattering enhancement factor f
                      (RH,lambda) is the key parameter to describe the effect of
                      RH on sigma(sp)(lambda) and is defined as
                      sigma(sp)(RH,lambda) measured at a certain RH divided by the
                      dry sigma(sp)(dry,lambda). The measurement of f (RH,lambda)
                      together with the dry absorption measurement (assumed not to
                      change with RH) allows the determination of the actual
                      extinction coefficient sigma(ep)(RH,lambda) at ambient RH.
                      In addition, a wide range of other aerosol properties were
                      measured in parallel. The measurements were used to
                      characterize the effects of RH on the aerosol optical
                      properties. A closure study showed the consistency of the
                      aerosol in-situ measurements. Due to the large variability
                      of air mass origin (and thus aerosol composition) a simple
                      parameterization of f (RH,lambda) could not be established.
                      If f (RH,lambda) needs to be predicted, the chemical
                      composition and size distribution need to be known.
                      Measurements of four MAX-DOAS (multi-axis differential
                      optical absorption spectroscopy) instruments were used to
                      retrieve vertical profiles of sigma(ep)(lambda). The values
                      of the lowest layer were compared to the in-situ values
                      after conversion of the latter ones to ambient RH. The
                      comparison showed a good correlation of R-2 = 0.62-0.78, but
                      the extinction coefficients from MAX-DOAS were a factor of
                      1.5-3.4 larger than the insitu values. Best agreement is
                      achieved for a few cases characterized by low aerosol
                      optical depths and low planetary boundary layer heights.
                      Differences were shown to be dependent on the applied
                      MAX-DOAS retrieval algorithm. The comparison of the in-situ
                      extinction data to a Raman LIDAR (light detection and
                      ranging) showed a good correlation and higher values
                      measured by the LIDAR (R-2 = 0.82-0.85, slope of 1.69-1.76)
                      if the Raman retrieved profile was used to extrapolate the
                      directly measured extinction coefficient to the ground. The
                      comparison improved if only nighttime measurements were used
                      in the comparison (R-2 = 0.96, slope of 1.12).},
      keywords     = {J (WoSType)},
      cin          = {IEK-8},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {Atmosphäre und Klima},
      pid          = {G:(DE-Juel1)FUEK491},
      shelfmark    = {Meteorology $\&$ Atmospheric Sciences},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000288982300012},
      doi          = {10.5194/acp-11-2603-2011},
      url          = {https://juser.fz-juelich.de/record/20027},
}