Preprints
https://doi.org/10.5194/amt-2020-363
https://doi.org/10.5194/amt-2020-363

  21 Oct 2020

21 Oct 2020

Review status: a revised version of this preprint was accepted for the journal AMT and is expected to appear here in due course.

Applicability of the VisiSize D30 shadowgraph system for cloud microphysical measurements

Jakub L. Nowak1,, Moein Mohammadi1,, and Szymon P. Malinowski1 Jakub L. Nowak et al.
  • 1Institute of Geophysics, Faculty of Physics, University of Warsaw, Warsaw, 02-293, Poland
  • These authors contributed equally to this work.

Abstract. The commercial shadowgraph system, Oxford Lasers VisiSize D30, originally designed to characterize industrial and agricultural sprays, was tested with respect to the application for measuring cloud microphysical properties, such as droplet size distribution and number concentration. Laboratory experiment with a dense stream of poly-disperse cloud-like droplets indicated strong dependence of the depth of field, thus also sample volume, on particle size. This relationship was determined and a suitable correction method was developed to improve estimations of droplet number concentration and size distribution. Spatial homogeneity of detection probability inside the sample volume and minimum droplet diameter providing uniform detection were examined. The second experiment with mono-disperse droplets produced by Flow-Focusing Monosized Aerosol Generator (FMAG) verified sizing accuracy and demonstrated reasonable agreement between the instruments. Effects of collisions and evaporation of droplets produced by FMAG were observed. Finally, the instrument was applied to sample atmospheric clouds at a ground-based mountain observatory and performed reliably during 3 week long field experiment. Based on the laboratory and field tests, recommendations concerning the use of the instrument for cloud droplet measurements were formulated.

Jakub L. Nowak et al.

 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Jakub L. Nowak et al.

Jakub L. Nowak et al.

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Short summary
The commercial instrument designed to characterize sprays, based on shadowgraphy imaging, was applied to measure number concentration and size distribution of cloud droplets. Laboratory and field tests were performed to verify the resolution, detection reliability and sizing accuracy. We developed the correction to data processing method which improves the estimation of cloud micro-physical properties. The paper concludes with recommendations concerning the usage in cloud physics studies.