| OCR Text |
Show - 8 - a certain substantial load is applied. Otherwise even a drop of strength may result. The higher the temperature gradient, the sooner the transformation is achieved, 3) Density, strength and crystalline features are interrelated to a certain extent. There are, however, snow samples which have similar specific gravity, yet quite different strength, and samples of different crystalline appearance may agree in more than one mechanical property, k) From experiments with plastic foils inserted as barriers in the snow it is concluded that a considerable vapor transfer is produced by the temperature gradient. As for the formation of depth hoar, a certain local turnover of incoming and outgoing vapor is necessary, but in a strong gradient depth hoar can develop between foils ( or ice sheets in nature) without convection of large scale. This investigation provided quantitative illumination of two points which are pertinent to the present discussion. One is the result of experiments with vapor varriers ( foils) in the snow sample which explicitly demonstrated the difference between large- scale and small- scale vapor transports the small- scale transport is able to effect extensive crystal alteration ( form depth hoar) without large- scale transport of mass from one part of the snow cover to another. The other point is the demonstrated complex interrelation among density, strength and crystal form ( and presumably heat properties such as conductivity). There are two aspects of heat and water vapor transfer in snow which are mentioned or implied in results of the researches discussed above, but which have not been explicitly treated by these authors. These are the temperature and pressure dependencies of vapor flux and its associated latent heat flux. |
