THE EFFECT OF CHANGE IN THERMAL-PROPERTIES ON THE PROPAGATION OF A PERIODIC THERMAL-WAVE - APPLICATION TO A SNOW-BURIED ROCKY OUTCROP

The propagation of a periodic thermal wave into snow is significantly altered by the presense of a shallow rock interface because of the lar ge difference in thermal properties of the two media. The temperature distribution is modeled using classical heat conduction equations subj ect to a periodic diurnal or seasonal surface heat flux condition, jum p conditions at the interface, and insulating conditions in the far-fi eld. The natural length scale (skin depth) over which order unity chan ges in temperature occur is proportional to the square root of the tim escale of the surface temperature variations. If the interface lies cl ose to or within the skin depth then large temperature gradients can b e sustained in the snow before temperature oscillations are forced thr ough to the underlying rock. These features are explained by an analyt ic one-dimensional periodic solution. A numerical algorithm is constru cted to solve for the temperature around plane two-dimensional rock ge ometries. The results show that during a period of atmospheric cooling the presence of a buried rocky outcrop increases the snow temperature and temperature gradients simultaneously to produce very favorable co nditions for crystal growth and avalanche formation.