Meteorologische Zeitschrift (Apr 1998)
A laser-optical device for measuring cloud and drizzle drop size distributions
Abstract
The Malvern Particle Sizer (MPS), a laser-optical device, was used for measuring cloud, drizzle and raindrops. In this paper it is shown that the instrument is suitable for investigations on cloud and drizzle droplet size distributions due to the need of high number concentrations in the measuring volume. Furthermore it is shown that with only two instruments (MPS and Joss-Waldvogel-disdrometer) the whole drop size range from small cloud drops up to large raindrops is detectable. During the field campaign FELDEX 95 at Kleiner Feldberg drop distributions were measured, both with the MPS and with a disdrometer. Two periods were investigated. Differences in the development of the cloud drop size spectra were observed, and could be attributed to totally different raindrop spectra. In one case broader cloud drop spectra led to rather narrow drizzle spectra with large concentrations of small raindrops, typical for warm rain formation. These spectra differ completely from the corresponding Marshall-Palmer (MP)-distributions. In the other case narrow cloud drop spectra were associated with broad raindrop spectra which were in good agreement with Marshall-Palmer-distributions. Differences in the rain formation processes can explain these observations. At the end some improvements of the MPS-system are discussed which would be helpful for future work to overcome problems that occurred during the field measurements.
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