Preprints
https://doi.org/10.5194/amt-2021-281
https://doi.org/10.5194/amt-2021-281

  27 Oct 2021

27 Oct 2021

Review status: this preprint is currently under review for the journal AMT.

Cloud microphysical measurements at a mountain observatory: comparison between shadowgraph imaging and phase Doppler interferometry

Moein Mohammadi1, Jakub Lukasz Nowak1, Guus Bertens2, Jan Molacek2, Wojciech Kumala1, and Szymon Piotr Malinowski1 Moein Mohammadi et al.
  • 1Institute of Geophysics, Faculty of Physics, University of Warsaw, Warsaw, 02-093, Poland
  • 2Max Planck Institute for Dynamics and Self-Organization, Goettingen, 37077, Germany

Abstract. The microphysical properties of cloud droplets, such as droplet size distribution and droplet number concentration, were studied. A series of field experiments were performed in the summer of 2019 at the Umweltforschungsstation Schneefernerhaus (UFS), an environmental research station located just below the peak of Mount Zugspitze in the German Alps. A VisiSize D30 manufactured by Oxford Laser Ltd., which is a shadowgraph imaging instrument, was utilized for the first time to measure the size and velocity of cloud droplets during this campaign. Furthermore, a phase Doppler interferometer (PDI) device, manufactured by Artium Tech. Inc., was simultaneously measuring cloud droplets. After applying modifications to the built-in software algorithms, the results from the two instruments show reasonable agreement regarding droplet sizing and velocimetry for droplet diameters larger than 13 µm. Moreover, discrepancies were observed concerning the droplet number concentration results, especially with smaller droplet sizes. Further investigation by applying appropriate filters to the data allowed the attribution of the discrepancies to two phenomena: the different optical performance of the sensors with regard to small droplets and high turbulent velocity fluctuations relative to the mean flow that result in an uncertain estimate of the volume of air passing through the PDI probe volume.

Moein Mohammadi et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-281', Anonymous Referee #2, 14 Nov 2021
  • RC2: 'Comment on amt-2021-281', Anonymous Referee #1, 16 Nov 2021

Moein Mohammadi et al.

Moein Mohammadi et al.

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Short summary
To compare two instruments, a VisiSize D30 shadowgraph system and a phase Doppler interferometer (PDI-FPDR), we performed a series of measurements of cloud droplet size and number concentration in orographic clouds. After applying essential modifications and filters to the data, the results from the two instruments showed better agreement in droplet sizing and velocimetry than droplet number concentration or liquid water content. Discrepancies were observed for droplets smaller than 13 microns.