Quicklooks of the „range corrected signal“ of our ALC (Automatic low-power lidar and ceilometer) testbed operated in the framework of ACTRIS:

• at 1064 nm measured by a Lufft CHM15kx (blueYALIS)
• at 905 nm by a Lufft CHM8k (redYALIS)
• at 910 nm by a Vaisala CL61
• at 910 nm by a Vasiala CL51
• at 910 nm by a Vaisala CL31
• at 912 nm by a Campbell Scientific SkyVUEPRO

In addtion, the Vaisala CL61 provides measurements of the Volume Linear Depolarization Ratio at 910 nm.

The instruments are usually located on the roof of the Meteorological Institute (MIM) of the Ludwig-Maximilians-Universität (48.148 N, 11.573 E, altitude 539 m), unless otherwise stated in the case of calibration or measurement campaigns.

We are grateful that we are allowed to process the corresponding data (since 1. June 2010) of the CHM15k ceilometer located at the Umweltforschungsstation Schneefernerhaus on Zugspitze (UFS, altitude 2712 m, 93 km south of Munich), owned by the UFS and operated by the German Weather Service for comparison.

The range corrected signal is proportional to the attenuated backscatter, and in first approximation proportional to the backscatter coefficient of particles. The backscatter coefficient is an indication for the „amount of aerosols“. The signals at 903 nm (redYALIS) are also influenced by water vapor absorption. The images show clouds in white (very strong backscatter signal) and aerosols in green and yellow (medium strong signal). Extended white and red areas down to the ground indicate rain. Note, that „steps“ in the colored areas (visible until 27. October 2014 for the blueYALIS measurements) are due to automatically changed settings of the ceilometer's detection unit.

• 12.06.2009 - 27.10.2014: CHM15kx „1. generation“
• 10.11.2014 - 08.01.2015: CHM15k „Nimbus“ (with overlap-correction provided by the manufacturer)
• 02.02.2015 - 26.05.2015: CHM15kx „Nimbus“
• 27.06.2015 - 14.09.2015: CHM15kx „Nimbus“ (after re-adjustment), CeiLinEx2015-campaign in Lindenberg
• 21.09.2015 - 12.11.2018: CHM15kx „Nimbus“
• 13.11.2018 - 03.06.2019: CHM15kx „Nimbus“ (with overlap-correction provided by the manufacturer)
• since 01.08.2019: CHM15kx „Nimbus“ (new detector, with overlap-correction provided by the manufacturer)

• since 25.02.2019: operational (range extended to 15 km)
• 11.09.2019-24.06.2020: located in Garching
• 24.06.2020-August 2020: located in Egling a.d. Paar on PV campaign site
• August 2020-April 2021: stored
• Since 20.04.2021: located at MIM

Examples with explanations are shown here

• 6. May 2011 (dominant aerosol layer, cirrus clouds)
• 1. August 2011 (low level clouds, mixing layer aerosol)

• On the calibration of ceilometer signals: Wiegner, M. and Geiß, A. (2012): Aerosol profiling with the Jenoptik ceilometer CHM15kx, Atmos. Meas. Tech., 5, 1953-1964, https://doi.org/10.5194/amt-5-1953-2012.
• On the evaluation of ceilometer data: Wiegner, M., Madonna, F., Binietoglou, I., Forkel, R., Gasteiger, J., Geiß, A., Pappalardo, G., Schäfer, K., and Thomas, W. (2014): What is the benefit of ceilometers for aerosol remote sensing? An answer from EARLINET, Atmos. Meas. Tech., 7, 1979-1997, https://doi.org/10.5194/amt-7-1979-2014.
• On water vapor absorption affecting ceilometer measurements at 905-910 nm: Wiegner, M. and Gasteiger, J. (2015): Correction of water vapor absorption for aerosol remote sensing with ceilometers, Atmos. Meas. Tech., 8, 3971–3984, https://doi.org/10.5194/amt-8-3971-2015.
• On the determination of the mixing layer height: Geiß, A., Wiegner, M., Bonn, B., Schäfer, K., Forkel, R., von Schneidemesser, E., Münkel, C., Chan, K. L., and Nothard, R. (2017): Mixing layer height as an indicator for urban air quality?, Atmos. Meas. Tech., 10, 2969-2988, https://doi.org/10.5194/amt-10-2969-2017.
• On the validation of the water vapor correction: Wiegner, M., Mattis, I., Pattantyús-Ábrahám, M., Bravo-Aranda, J. A., Poltera, Y., Haefele, A., Hervo, M., Görsdorf, U., Leinweber, R., Gasteiger, J., Haeffelin, M., Wagner, F., Cermak, J., Komínková, K., Brettle, M., Münkel, C., and Pönitz, K. (2019): Aerosol backscatter profiles from ceilometers: validation of water vapor correction in the framework of CeiLinEx2015, Atmos. Meas. Tech., 12, 471–490, https://doi.org/10.5194/amt-12-471-2019.