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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/amt-2019-491
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/amt-2019-491
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 09 Jan 2020

Submitted as: research article | 09 Jan 2020

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A revised version of this preprint is currently under review for the journal AMT.

Methodology for deriving the telescope focus function and its uncertainty for a heterodyne pulsed Doppler lidar

Pyry Pentikäinen1, Ewan James O'Connor2,3, Antti Juhani Manninen2, and Pablo Ortiz-Amezcua4,5 Pyry Pentikäinen et al.
  • 1Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, Helsinki, Finland
  • 2Finnish Meteorological Institute, Helsinki, Finland
  • 3Department of Meteorology, University of Reading, UK
  • 4Andalusian Institute for Earth System Research (IISTA-CEAMA), 18006, Granada, Spain
  • 5Department of Applied Physics, University of Granada, 18071 Granada, Spain

Abstract. Doppler lidars provide two measured parameters, radial velocity and signal-to-noise ratio, from which winds and turbulent properties are routinely derived. Attenuated backscatter, which gives quantitative information on aerosols, clouds, and precipitation in the atmosphere, can be used in conjunction with the winds and turbulent properties to create a sophisticated classification of the state of the atmospheric boundary layer. Calculating attenuated backscatter from the signal-to-noise ratio requires accurate knowledge of the telescope focus function, which is usually unavailable. Inaccurate assumptions of the telescope focus function can significantly deform attenuated backscatter profiles, even if the instrument is focused at infinity. Here, we present a methodology for deriving the telescope focus function using a co-located ceilometer for Halo Photonics Streamline and XR pulsed heterodyne Doppler lidars. The method derives two parameters of the telescope focus function, the effective beam diameter and the effective focal length of the telescope. Additionally, the method provides uncertainty estimates for the retrieved attenuated backscatter profile arising from uncertainties in deriving the telescope function, together with standard measurement uncertainties from the signal-to-noise ratio. The method is best suited for locations where the absolute difference in aerosol extinction at the ceilometer and Doppler lidar wavelengths is small.

Pyry Pentikäinen et al.

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Pyry Pentikäinen et al.

Pyry Pentikäinen et al.

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Latest update: 30 Mar 2020
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Short summary
We provide a methodology for obtaining a function describing how the Doppler lidar telescope configuration impacts the measurements. Together with the function itself, we also provide the uncertainties in the function, which propagate through to provide uncertainties in the geophysical quantities obtained from the measurements. The method can be used to determine how stable the instrument is over time, and also identify if changes have been made in the instrument setup.
We provide a methodology for obtaining a function describing how the Doppler lidar telescope...
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