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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Discussion papers | Copyright
https://doi.org/10.5194/amt-2018-307
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 17 Oct 2018

Research article | 17 Oct 2018

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This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).

Aerosol backscatter profiles from ceilometers: validation of water vapor correction in the framework of CeiLinEx2015

Matthias Wiegner1, Ina Mattis2, Margit Pattantyús-Ábrahám2,a, Juan Antonio Bravo-Aranda3,b, Yann Poltera4,c, Alexander Haefele4, Maxime Hervo4, Ulrich Görsdorf5, Ronny Leinweber5, Josef Gasteiger6, Martial Haeffelin3, Frank Wagner2,d, Jan Cermak7,e,f, Katerina Komínková8, Mike Brettle9, Christoph Münkel10, and Kornelia Pönitz11 Matthias Wiegner et al.
  • 1Meteorologisches Institut, Ludwig-Maximilians-Universität, Theresienstraße 37, 80333 München, Germany
  • 2Deutscher Wetterdienst, Meteorologisches Observatorium Hohenpeißenberg, Hohenpeißenberg, Germany
  • 3Institut Pierre Simon Laplace, École Polytechnique, CNRS, Université Paris–Saclay, Palaiseau, France
  • 4MeteoSwiss, Payerne, Switzerland
  • 5Deutscher Wetterdienst, Meteorologisches Observatorium Lindenberg, Lindenberg, Germany
  • 6Faculty of Physics, University of Vienna, Vienna, Austria
  • 7Department of Geography, Ruhr-Universität Bochum, Bochum, Germany
  • 8Global Change Research Institute, Czech Academy of Sciences, Brno, Czech Republic
  • 9Chartered meteorologist, UK
  • 10Vaisala GmbH, Hamburg, Germany
  • 11G. Lufft Mess- und Regeltechnik GmbH, Fellbach, Germany
  • anow at: Federal Office for Radiation Protection, Department of Environmental Radiation, Neuherberg, Germany
  • bnow at: University of Granada, Granada, Spain
  • cnow at: Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
  • dnow at: Karlsruhe Institute of Technology (KIT), IMK–TRO, Eggenstein-Leopoldshafen, Germany
  • enow at: Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research, Karlsruhe, Germany
  • fnow at: Karlsruhe Institute of Technology (KIT), Institute of Photogrammetry and Remote Sensing, Karlsruhe, Germany

Abstract. With the rapidly growing number of automated single-wavelength backscatter lidars (ceilometers) their potential benefit for aerosol remote sensing received considerable scientific attention. When studying the accuracy of retrieved particle backscatter coefficients it must be considered that most of the ceilometers are influenced by water vapor absorption in the spectral range around 910nm. In the literature methodologies to correct for this effect have been proposed, however, a validation was not yet performed. In the framework of the ceilometer intercomparison campaign CeiLinEx2015 in Lindenberg, Germany, hosted by the German Weather Service, it was possible to tackle this open issue. Ceilometers from Lufft (CHM15k and CHM15kx, operating at 1064nm), from Vaisala (CL51 and CL31) and from Campbell Scientific (CS135), all operating at a wavelength of approximately 910nm, were deployed together with a multi-wavelength research lidar (RALPH) that served as reference. In this paper the validation of the water vapor correction is performed by comparing ceilometer backscatter signals with measurements of the reference system extrapolated to the water vapor regime. One inherent problem of the validation is the spectral extrapolation of particle optical properties. For this purpose AERONET measurements and inversions of RALPH signals were used. Another issue is that the vertical range where validation is possible is limited to the upper part of the mixing layer due incomplete overlap, and the in general low signal to noise ratio and signal artefacts above that layer. Our intercomparisons show that the water vapor correction leads to a quite good agreement between the extrapolated reference signals and the measurements in the case of CL51 ceilometers at one or more wavelengths in the specified range of the laser diode's emission. This equivocation is due to the similar effective water vapor transmission at several wavelengths. In the case of CL31 and CS135 ceilometers the validation was not always successful. That suggests that error sources beyond the water vapor absorption might be dominant. For future applications we recommend to monitor the emitted wavelength and to provide dark measurements on a regular basis.

Matthias Wiegner et al.
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Short summary
Ceilometers are often influenced by water vapor absorption in the spectral range around 910 nm. Thus, a correction is required to retrieve aerosol optical properties. Validation of this correction scheme was performed in the framework of CeiLinEx2015 for several ceilometers with good agreement in case of CL51 ceilometers. For future applications we recommend to monitor the emitted wavelength and to provide dark measurements on a regular basis to be able to correct for signal artefacts.
Ceilometers are often influenced by water vapor absorption in the spectral range around 910 nm....
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