WG3/4 ALC subgroup: optical overlap of the Lufft CHM15k

subgroup meetings
Date: Monday, 13 December 2021 14:00 - 15:30

Venue: online

The attenuated backscatter profiles recorded by the Ott/Lufft CHM15k are affected by an incomplete optical overlap in the lowest few hundred metres. Studies have shown that correction solely based on the overlap function provided by the manufacturer may not always be sufficient to obtain high-quality data. Accounting for the temperature dependence of the optical overlap function using the method developed by Hervo et al. (2016) has been shown to significantly improve the observed profile of attenuated backscatter. As a consequence, it is suggested that advanced products that are based on the backscatter profiles, such as aerosol characteristics or atmospheric boundary layer heights should utilise data corrected with the dynamic overlap model, rather than the static approach (Kotthaus et al., 2020; Poltera et al., 2017).

In this special working group meeting we are going to identify the necessary steps required to reach fully-automated creation of the temperature-dependant optical overlap model for Lufft CHM15k observations.

The SWG is motivated by high demand for high-quality attenuated backscatter profiles and associated advanced products across diverse sensor networks such as ACTRIS and E-PROFILE.



Hervo, M., Poltera, Y., Haefele, A., 2016. An empirical method to correct for temperature-dependent variations in the overlap function of CHM15k ceilometers. Atmos. Meas. Tech. 9, 2947–2959. doi:10.5194/amt-9-2947-2016

Kotthaus, S., Haeffelin, M., Drouin, M.-A., Dupont, J.-C., Grimmond, S., Haefele, A., Hervo, M., Poltera, Y., Wiegner, M., 2020. Tailored Algorithms for the Detection of the Atmospheric Boundary Layer Height from Common Automatic Lidars and Ceilometers (ALC). Remote Sens. 12, 3259. doi:10.3390/rs12193259

Poltera, Y., Martucci, G., Collaud Coen, M., Hervo, M., Emmenegger, L., Henne, S., Brunner, D., Haefele, A., 2017. PathfinderTURB: an automatic boundary layer algorithm. Development, validation and application to study the impact on in situ measurements at the Jungfraujoch. Atmos. Chem. Phys. 17, 10051–10070. doi:10.5194/acp-17-10051-2017