【摘要】 <正>多年冻土是岩石经过地表与大气圈之间热交换的产物,在这种交换过程中,各种地质地理因素都不同程度地促进或削弱了多年冻土的形成和退化。季节性积雪在空间上位于大气圈和岩石圈之间,在时间上主要集中于地表散热时期。因此,它在气-地热交换过程中起着不可低估的作用,对多年冻土的形成、退化及分布有着直接的影响。更多还原

【Abstract】 This paper mainly deals with the influence of snow cover on the lower limit of permafrost in Altai Mountains. Investigation reveals that the mean annual air temperature at the lower limit of permafrost in Altai Mountains is -5.4℃, 2 to 4℃ lower than that at the lower limit of alpine permafrost in North Hemisphere. Through investigations of snow cover it was observed that the heat preserving effect of snow decreases the seasonally frozen depth in winter; conversely, in summer snow has little effect on seasonally thawed depth, and even promotes thawing. Thus seasonally thawed depth is greater than seasonally frozen depth. The difference between these two is the latent seasonally thawed depth (△H) which results from seasonal snow accumulation. The appearence of △H shows that, in the course of the air-ground heat exchange,the energy absorption of ground surface is greater than its release. The internal energy of permafrost increases. It makes the temperature (tcp)of the permafrost at the depth of zero annual amplitude rise, and eventually the permafrost degenerate.更多还原