On the spatial variability of the regional aerosol distribution as determined from ceilometers

Abstract

<p><strong>Abstract.</strong> Measurements of the vertical distribution of aerosol particles are typically only available at selected sites leaving the question of their representativeness for urban and regional scales unanswered. As a contribution to solve this problem we have investigated ceilometer signals from two testbeds in Munich and Berlin, Germany. For each testbed measurements of 24 months from 6 ceilometers were available. This constitutes a unique data set, in particular as the same type of instruments are deployed and the same data evaluation schemes applied. Two parameters are discussed: the mixing layer height (MLH) as an indicator for the vertical distribution and the integrated backscatter as a proxy for the amount of aerosols in the mixing layer. The MLH was determined by the COBOLT algorithm, the integrated backscatter from the Klett (backward and forward) inversion scheme. It was found that the mean difference of the MLH at two sites within a testbed typically only varies by less than 50 m, slightly increasing with the distance of the corresponding sites. Almost 60 % of all intercomparisons agree within ±100 m. MLHs are typically correlated with <i>R</i> > 0.9 in particular for the Berlin-testbed. With respect to the integrated backscatter the correlation is in the range of 0.7 < <i>R</i> < 0.9. This is expected from the diversity of local aerosol sources within a given testbed. We conclude from our data that the MLH determined from a single ceilometer is applicable for a whole metropolitan area. However, the integrated backscatter of particles within the mixing layer exhibits a variability of 15–25 % suggesting that one ceilometer is not representative, especially if atmospheric processes shall be investigated.</p>

Impact of the 2020 COVID-19 lockdown on NO2 and PM10 concentrations in Berlin, Germany

“…The mixing layer height (MLH) in km was derived from ceilometer measurements on the rooftop of the main building of Technische Universität, which belongs to the Urban Climate Observatory (UCO) Berlin for long-term observations of atmospheric processes in cities ( Scherer et al, 2019 ). The COBOLT algorithm was used to determine the MLH at 15 sec resolution and aggregated to hourly values ( Wiegner et al, 2020 ). The data were available from January 2018 until the end of August 2020, therefore not covering the entire year 2017 and the remainder of 2020.…”

Development of an atmospheric chemistry model coupled to the PALM model system 6.0: Implementation and first applications

“…In addition to near surface observations from online web sources Thorsen (2017), we also analysed radiosonde data from Lindenberg (Oolman, 2017) (last accessed on 30.07.2020), and aerosol backscatter observations from Ceilometer for 16 and 17 July 2017, to understand the vertical structure of the atmosphere in the area of interest. Ceilometer observations of aerosol back-scatter profiles were performed at the roof of the TU Campus Charlottenburg building (52.5123 • N, 13.3279 • E) as part of the Urban Climate Observatory (UCO) operated by the Chair of Climatology at Technische Universität Berlin for long-term observations of atmospheric processes in cities (Scherer et al, 2019a;Wiegner et al, 2002)) and contribute to the research program Urban Climate Under Change [UC]2 (Scherer et al, 2019b). Mixing layer heights were derived from the aerosol backscatter signal according to Geiß et al (2017).…”