Effect of Seasonality of Snow Accumulation and Melt on Snow Surface Energy Exchanges at a Continental Alpine Site

摘要

Snow surface energy exchanges and snowmelt were measured during the 1994 and l995 snowmelt seasons at an alpine site in the Colorado Front Range (3517 m MSL, 40°03'N, 105°35'W). Following a maximum accumulation of 0.49-m snow water equivalence (SWE), the 1994 snowmelt season began on 5 May and lasted 32 days until 6 June. In contrast, the 1995 maximum accumulation of 1.31-m SWE did not occur until 1 June, and the snowmelt season lasted 45 days until July 16. Thus, a nearly threefold larger snowpackablated in only 41% more time in the later 1995 snowmelt season. In 1994, net radiation accounted for 75% of the energy available to melt snow, and sensible and latent heat fluxes accounted for the remaining 25%. During the 1995 snowmelt season the meanair temperature was warmer ( + 1.3°C) and the mean specific humidity was greater (+0.6 g kg~(-1)) than during the 1994 snowmelt season. As a result, in 1995, sensible and latent heat fluxes accounted for 54% of the energy for snowmelt and net radiationaccounted for only 46%. Midday maximum snowmelt rates were approximately equal in 1994 and 1995; the overall more rapid 1995 melt rate was due to the frequent occurrence of nocturnal melting, which did not occur in 1994. The large differences between these two snowmelt seasons provide analogies for understanding regional variability of snowmelt processes and for understanding alpine snowmelt response to climate variability and change.