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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2016-962
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
23 Jan 2017
Review status
A revision of this discussion paper was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
PathfinderTURB: an automatic boundary layer algorithm. Development, validation and application to study the impact on in-situ measurements at the Jungfraujoch
Yann Poltera1,3, Giovanni Martucci1, Martine Collaud Coen1, Maxime Hervo1, Lukas Emmenegger2, Stephan Henne2, Dominik Brunner2, and Alexander Haefele1 1Federal Office of Meteorology and Climatology, MeteoSwiss, Payerne, Switzerland
2Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
3Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
Abstract. Continuous observations of the vertical structure of the planetary boundary layer are invaluable for the validation of atmospheric transport models on the micro and meso scale. Lidar and ceilometer backscatter observations offer a robust technique with growing spatial coverage, but the obtained backscatter profiles need to be carefully translated into boundary layer parameters. Here we present the development of the PathfinderTURB algorithm for the analysis of ceilometer backscatter data and the real-time detection of the vertical structure of the planetary boundary layer. Two typical aerosol layer heights are retrieved by PathfinderTURB: the Convective Boundary Layer (CBL) and the Continuous Aerosol Layer (CAL). PathfinderTURB combines the strengths of gradient- and variance-based methods and addresses the layer attribution problem by adopting a geodesic approach. The algorithm has been applied to one year of data measured by two CHM15k ceilometers operated at the Aerological Observatory of Payerne (491 m, a.s.l.) on the Swiss plateau, and at the Kleine Scheidegg (2061 m, a.s.l.) in the Swiss Alps. The retrieval of the CBL has been validated at Payerne using two reference methods: (1) manual detections of the CBL height performed by independent human experts using the ceilometer backscatter data of the year 2014; (2) values of CBL heights calculated using the Richardson's method from co-located radio sounding data. We found average biases as small as 27 m (53 m) with respect to reference method 1 (2). Based on the excellent agreement with the two reference methods, PathfinderTURB has been applied to the ceilometer data at the mountainous site of the Kleine Scheidegg for the period September 2014 till November 2015. At this site, the CHM15k is operated in a novel, tilted configuration at 71° zenith angle to probe the air next to the Sphinx Observatory (3580 m, a.s.l.) on the Jungfraujoch (JFJ). The analysis of the retrieved layers led to the following results: the CAL reaches the JFJ during 41 % of the time in summer and during 21 % of the time in winter for a total of 97 days during the two seasons. The season-averaged daily cycles show that the CBL height reaches the JFJ only during short periods (4 % of the time) on 20 individual days in summer and never during winter. Especially during summer the CBL and the CAL modify the air sampled in-situ at JFJ, resulting in an unequivocal dependence of the measured absorption coefficient on the height of both layers. This highlights the relevance of retrieving the height of CAL and CBL in mountainous regions.

Citation: Poltera, Y., Martucci, G., Collaud Coen, M., Hervo, M., Emmenegger, L., Henne, S., Brunner, D., and Haefele, A.: PathfinderTURB: an automatic boundary layer algorithm. Development, validation and application to study the impact on in-situ measurements at the Jungfraujoch, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2016-962, in review, 2017.
Yann Poltera et al.
Yann Poltera et al.

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Short summary
We present the PathfinderTURB algorithm for the analysis of ceilometer backscatter data and the real-time detection of the vertical structure of the planetary boundary layer. PathfinderTURB has been applied to 1 year data measured by two ceilometers operated at 2 Swiss stations: the Aerological Observatory of Payerne on the Swiss plateau, and the Alpine Jungfraujoch observatory. The study shows that aerosols from the boundary layer influence significantly the air measured at Jungfraujoch.
We present the PathfinderTURB algorithm for the analysis of ceilometer backscatter data and the...
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