Size-distribution of ice crystals in cumulonimbus clouds

✍ Scribed by R. F. Jones

• Book ID: 104573035
• Publisher: John Wiley and Sons
• Year: 1960
• Tongue: English
• Weight: 457 KB
• Volume: 86
• Category: Article
• ISSN: 0035-9009
• DOI: 10.1002/qj.49708636808

✦ Synopsis

Abstract

Ice‐crystal size‐distributions have been measured in clouds associated with the intertropical convergence zone and more isolated cumulonimbus clouds in temperate zones. Mean size‐distributions fit curves N~D~ = 1,000/D^3^ and N~D~ = 1,000/D^2·3^ in tropical and temperate clouds respectively where N~D~ δD is the number per m^3^ with diameters between D and D + δD mm. The tropical curve is a close fit throughout the measured range of D (0·05 to 4 mm) but the temperate curve is applicable in the range up to D = 2 mm only, there‐after a curve N~D~ = 10,000/__D__5·4 fits the curve for D = 2 to 5 mm. In temperate clouds there is little variability with temperature except for a decrease in size of the largest particles observed as temperature decreases.

There is some evidence that the particles caught are graupel of mean density 0·6 g cm^−3^ and, on this assumption, variation with total ice‐crystal concentration suggests an empirical distribution law for particles with diameters 0·25 mm or greater of \documentclass{article}\pagestyle{empty}\begin{document}$ N_D = 10^{4.1} \exp [ - \frac{{2.67}}{{W^{\frac{1}{3}} }}(D - 0.25)] $\end{document} where W is the ice‐crystal content in g m^−3^.