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https://doi.org/10.5194/amt-2017-53
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
07 Apr 2017
Review status
A revision of this discussion paper is under review for the journal Atmospheric Measurement Techniques (AMT).
Mixing layer height as an indicator for urban air quality?
Alexander Geiß1,a, Matthias Wiegner1, Boris Bonn2,b, Klaus Schäfer3, Renate Forkel3, Erika von Schneidemesser2, Christoph Münkel4, Ka Lok Chan1, and Rainer Nothard5 1Ludwig-Maximilians-Universität (LMU Munich), Meteorological Institute, Theresienstraße 37, 80333 München, Germany
2Institute for Advanced Sustainability Studies (IASS), Berliner Straße 130, 14467 Potsdam, Germany
3Karlsruhe Institute of Technology (KIT) – Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Kreuzeckbahnstraße 19, 82467 Garmisch-Partenkirchen, Germany
4Vaisala GmbH, Weather Instruments, Notkestraße 11, 22607 Hamburg, Germany
5Senate Department for Urban Development and the Environment, Brückenstraße 6, 10179 Berlin, Germany
anow at: ESA ESTEC, Keplerlaan 1, 2201AZ Noordwijk, The Netherlands
bnow at: Albert-Ludwig-University, Institute for Forest Sciences, Georges-Köhler-Allee 53, 79110 Freiburg, Germany
Abstract. The mixing layer height (MLH) is a measure for the vertical turbulent exchange within the boundary layer, which is one of the controlling factors for the dilution of pollutants emitted near the ground. Based on continuous MLH measurements with a Vaisala CL51 ceilometer and measurements from an air quality network, the relationship between MLH and near surface pollutant concentrations have been investigated. In this context the uncertainty of the MLH retrievals and the representativeness of ground-based in-situ measurements are crucial. We have investigated this topic by using data from the BAERLIN2014 campaign in Berlin, Germany, conducted during June and August 2014. To derive the MLH three versions of the proprietary software BL-VIEW and a novel approach COBOLT were compared. It was found that the overall agreement is reasonable if mean diurnal cycles are considered. The main advantage of COBOLT is the continuous detection of the MLH with a temporal resolution of 10 minutes and a lower number of cases when the residual layer is misinterpreted as mixing layer. We have calculated correlations between MLH as derived from the different retrievals and concentrations of pollutants (PM10, O3 and NOx) for different locations in the metropolitan area of Berlin. It was found that the correlations with PM10 are quite different for different sites without showing a clear pattern, whereas the correlation with NOx seems to depend on the vicinity of emission sources in main roads. In case of ozone as a secondary pollutant a clear correlation was found. We conclude that the effects of the heterogeneity of the emission sources, chemical processing and mixing during transport exceed the differences due to different MLH retrievals. Moreover, it seems to be unrealistic to find correlations between MLH and near surface pollutant concentrations representative for a city like Berlin, in particular when traffic emissions are dominant. Nevertheless it is worthwhile to use advanced MLH retrievals for ceilometer data, e.g. for the validation of chemical transport models.

Citation: Geiß, A., Wiegner, M., Bonn, B., Schäfer, K., Forkel, R., von Schneidemesser, E., Münkel, C., Chan, K. L., and Nothard, R.: Mixing layer height as an indicator for urban air quality?, Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2017-53, in review, 2017.
Alexander Geiß et al.
Alexander Geiß et al.
Alexander Geiß et al.

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Short summary
Based on measurements with a ceilometer and from an air quality network, the relationship between the mixing layer height (MLH) and near surface concentrations of pollutants were investigated. We found that the effects of the heterogeneity of the emission sources, chemical processing and mixing during transport exceed the differences due to different MLH-retrievals. It seems to be unrealistic to find correlations between MLH and concentrations representative for an entire metropolitan area.
Based on measurements with a ceilometer and from an air quality network, the relationship...
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