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Effects of cloud‐droplet spectra on the average surface‐temperature of ice accreted on fixed cylindrical collectors
Author(s) -
Avila E. E.,
Castellano N. E.,
Saunders C. P. R.
Publication year - 1999
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49712555515
Subject(s) - graupel , ice crystals , materials science , convection , mechanics , supercooling , liquid water content , volume (thermodynamics) , heat transfer , meteorology , thermodynamics , atmospheric sciences , physics , cloud computing , computer science , operating system
An experimental study of the heat balance of a stationary cylindrical collector accreting supercooled water droplets has shown a new dependence on the sizes of the water droplets in the laboratory cloud. In a study in 1967, MacKlin and Payne related the steady‐state heat‐release during accretion to the heat loss by convection and conduction; their equation involved a numerical factor χ for which they assumed a value of 0.28. the present study has shown that χ is a function of the droplet spectrum with values around 0.5 at a velocity of 4 m s‐ 1 for a mean volume‐weighted droplet‐diameter of 18 μm, and that χ approaches 0.3 for droplets greater than 30 μm diameter. the results have importance to the surface temperatures of riming graupel pellets and hailstones in convective storms which, in the presence of small water‐droplets, will be heated to a smaller degree than has been assumed in current models of hailstone growth. Furthermore, the effect of droplet size may influence ice‐crystal multiplication and charge transfer in convective clouds, both of which are highly temperature dependent.