“Commonly used disdrometers tend not to accurately measure concentrations of very small drops in the raindrop size distribution (DSD), either through truncation of the DSD at the small-drop end or because of large uncertainties on these measurements. Recent studies have shown that, as a result of these inaccuracies, many if not most ground-based disdrometers do not capture the ‘drizzle mode’ of precipitation, which consists of large concentrations of small drops and is often separated from the main part of the DSD by a shoulder region.”
– explains a report in the Journal of Applied Meteorology and Climatology, Jan. 2019. The authors propose a solution to such problems :
“We present a technique for reconstructing the drizzle mode of the DSD from ‘incomplete’ measurements in which the drizzle mode is not present.”
See: Reconstructing the Drizzle Mode of the Raindrop Size Distribution Using Double-Moment Normalization, Journal of Applied Meteorology and Climatology, Jan. 2019
Note: If the water droplet size is below 20 micrometers (or so) it’s not drizzle, it’s fog. [Ref : Pruppacher H., Klett J. (2010) Microstructure of Atmospheric Clouds and Precipitation. In: Microphysics of Clouds and Precipitation. Atmospheric and Oceanographic Sciences Library, vol 18.]
BONUS: The internationally recognized symbols for drizzle(s) can be found here.
Photo: Courtesy Wikipedia
Research research: Martin Gardiner