Klaus Schäfer is physicist and retired from the Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research in Garmisch-Partenkirchen, Germany in 2016. He is working since more than 45 years in atmospheric research and currently at investigations of meteorological influences upon air quality, mainly by remote sensing. He is teaching atmospheric physics for the atmospheric environmental research at the School of Atmospheric Sciences of the Chengdu University of Information Technology, Chengdu, China since 2016. Until 2020 he was technical leader of the project “Smart Air Quality Network”, funded by the German Federal Ministry of Transport and digital Infrastructure. He was supervisor of 17 Doctorial and 20 master's or Diploma students as well as coordinated about 60 research projects of national and international funding organisations and companies. His total number of publications in Web of Science is 172 and h-index is 31 (Researcher ID A-6173-2013).
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These reasons prompted the Commission on Air Pollution Prevention of VDI and DIN (a standards committee of the German Standards Institute) to establish the German Standards VDI 4211 and 4212 on these techniques. Both Standards are also intended to support and encourage manufacturers and start-ups to develop and produce marketable instruments in consideration of future air monitoring concepts (small, mobile, versatile, multi-component analysers). In order to pave the way for these methods to be recognized by the authorities as equivalent methods to established air quality monitoring methods experience-based minimum requirements for selected performance characteristics are recommended which may be the basis for a future type testing procedure.
The SmartAQnet research initiative focuses on the subject of data access and data-based applications. Such complex monitoring provides the basis of deeper process understanding of air pollution exposure. The network architecture is shown and first results about spatial variation of meteorological influences upon air pollution exposure is presented using ceilometer, UAV and the existing monitoring network data.
Since 2006 different methods for long-term continuous remote sensing of mixing layer height (MLH) are operated in Augsburg. The Vaisala ceilometers LD40 and CL31 are used which are eye-safe commercial mini-lidar systems. The ceilometer measurements provide information about the range-dependent aerosol concentration; gradient minima within this profile mark the borders of mixed layers. Special software for these ceilometers provides routine retrievals of lower atmosphere layering from vertical profiles of laser backscatter data. The radiosonde data from the station Oberschleissheim near Munich (about 50 km away from Augsburg city) are also used for MLH determination. The profile behavior of relative humidity (strong decrease) and virtual potential temperature (inversion) of the radiosonde agree mostly well with the MLH indication from ceilometer laser backscatter density gradients.
A RASS (Radio-Acoustic Sounding System) from Metek is applied which detects the height of a turbulent layer characterized by high acoustic backscatter intensities due to thermal fluctuations and a high variance of the vertical velocity component as well as the vertical temperature profile from the detection of acoustic signal propagation and thus temperature inversions which mark atmospheric layers. These data of RASS measurements are the input for a software-based determination of MLH. A comparison of the results of the remote sensing methods during simultaneous measurements was performed. The information content of the different remote sensing instruments for MLH in dependence from different weather classes was analyzed further. A special focus is the continuous determination of MLH.
The information about atmospheric layering is continuously monitored by uninterrupted remote sensing measurements with the Vaisala ceilometer CL51 which is an eye-safe commercial mini-lidar system. Special software for this ceilometer provides routine retrievals of lower atmosphere layering from vertical profiles of laser backscatter data.
An intensive measurement period during the winter 2011/2012 is studied. The meteorological influences upon air pollutant concentrations are investgated and the correlations of air pollutant concentrations with ceilometer MLH are determined. Benzene was detected by department of Applied Climatology and Landscape Ecology, University of Duisburg-Essen (UDE) with a gas chromatograph during the measurement period. The meteorological data are collected by UDE and the monitoring station Essen of the German national meteorological service DWD. The concentrations of the air pollutants NO, NO2 and PM10 are provided by the national air pollution network LANUV.
Detection of emission indices of aircraft exhaust compounds by open-path optical methods at airports
Aerosol concentration measurements with a lidar ceilometer: results of a one year measuring campaign
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