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Proceedings Paper

Results from long-term detection of mixing layer height: ceilometer and comparison with Radio-Acoustic Sounding System
Author(s): Klaus Schäfer; Stefan Emeis; Carsten Jahn; Michael Tuma; Christoph Münkel; Peter Suppan
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Paper Abstract

The mixing layer height (MLH) is an important factor which influences exchange processes of ground level emissions. The continuous knowledge of MLH is supporting the understanding of processes directing air quality. If the MLH is located near to the ground, which occurs mainly during winter and night-time, air pollution can be high due to a strongly limited air mass dilution.

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.

Paper Details

Date Published: 1 November 2012
PDF: 8 pages
Proc. SPIE 8534, Remote Sensing of Clouds and the Atmosphere XVII; and Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing VIII, 853408 (1 November 2012); doi: 10.1117/12.974327
Show Author Affiliations
Klaus Schäfer, Karlsruher Institut für Technologie (Germany)
Stefan Emeis, Karlsruher Institut für Technologie (Germany)
Carsten Jahn, Karlsruher Institut für Technologie (Germany)
Michael Tuma, Karlsruher Institut für Technologie (Germany)
Christoph Münkel, Vaisala GmbH (Germany)
Peter Suppan, Karlsruher Institut für Technologie (Germany)

Published in SPIE Proceedings Vol. 8534:
Remote Sensing of Clouds and the Atmosphere XVII; and Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing VIII
Upendra N. Singh; Evgueni I. Kassianov; Gelsomina Pappalardo; Adolfo Comeron; Richard H. Picard; Klaus Schäfer, Editor(s)

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