. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography March 1974 D I \ \ I [..Will AND WILLIAM I) . M "t>| I 571 and Scott present measured values of the linear growth rates which show these alternations in terms of maxima and minima in the growth curves. It should be realized, however, that it is only the relative growth rates which are of concern in under- standing the origins of the primary habits. A con- venient measure for the relative rates is the condensa- tion coefficient a defined bv w
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography March 1974 D I \ \ I [..Will AND WILLIAM I) . M "t>| I 571 and Scott present measured values of the linear growth rates which show these alternations in terms of maxima and minima in the growth curves. It should be realized, however, that it is only the relative growth rates which are of concern in under- standing the origins of the primary habits. A con- venient measure for the relative rates is the condensa- tion coefficient a defined bv where G,nax=QSF (1) (2) is the maximum growth rate possible at the net im- pingement flux 5/\ and V. is the volume of a water molecule in the lattice. The net impingement flux is related to the local supersaturation 5 by j=- SF (3) where FS(T) is the molecular flux hitting the surface at equilibrium. If bP is the corresponding excess vapor pressure, then from the kinetic theory of gases 8P 6F = (lirmkT)* â =kTbP, (4) in which k is Boltzmann's constant, kr is defined as the kinetic theory factor, m is the mass of a water molecule, and T the temperature. From these equations the condensation coefficient can be calculated from linear growth rate data at known values of temperature and excess pressure (supersaturation). The trends with temperature so obtained from the data of Lamb and Scott are shown in Fig. 1. The overall trends to these curves are, of course, similar to those of the linear growth rates and cross at the temperatures ( â and â ) which define the transitions between the primary habit regimes of plates and columns within the data range (Lamb and Hobbs, 1971). The condensation coefficient may be interpreted as the fraction of impinging vapor molecules which are successful at actually being incorporated into the ice lattice. The trends of Fig. 1 thus show how strongly the probability of incorporation varies with temperature on the basal and prism faces of ice
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