Item: Roughness effect on vapor transfer for surface hoar growth
Title: Roughness effect on vapor transfer for surface hoar growth
Proceedings: Proceedings of the 2000 International Snow Science Workshop, October 1-6, Big Sky, Montana
Authors: Akihiro Hachikubo, Kitami Institute of Technology, Kitami, Japan
Abstract: In order to examine the roughness effect of surface hoar crystals on their growth and obtain a relation between surface roughness and the amount of sublimation, field observations of surface hoar formation were carried out in the three seasons of 1993 to 1996 in Hokkaido, northern Japan. The sublimation rate increased linearly with the product of the vapor pressure gradient and the wind speed. This relation made it possible to estimate the sublimation rate of surface hoar by a bulk method from the meteorological data. The bulk transfer coefficient of water vapor was roughly constant ((2.4 x 10-3, dimensionless) when the surface hoar crystals were small, whereas it showed some increase as the hoar crystals grew to several millimeters in height. The coefficient was expressed as (2.0+9S) x 10-3, where S (kg m-2) is the total amount of sublimation, or (2.0+0.4d) x10-3, where d (mm) is the major axis of surface hoar crystal. These relation indicate that a positive feedback system exists on the mechanism of surface hoar formation.
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Keywords: surface hoar, bulk transfer coefficient, surface roughness
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