Temperature Patterns in an Alpine Snow Cover and Their Influence on Snow Metamorphism.

• Main Authors: LaChapelle,Edward R, Armstrong,Richard L
• Other Authors: COLORADO UNIV BOULDER INST OF ARCTIC AND ALPINE RESEARCH
• Format: Text
• Language: English
• Published: 1977
• Subjects: Meteorology; Snow; Ice and Permafrost; *SNOW COVER; *TEMPERATURE GRADIENTS; DENSITY; TEMPERATURE; CRYSTAL STRUCTURE; LAYERS; ATMOSPHERIC TEMPERATURE; COOLING; DEPTH; STRENGTH(MECHANICS); ICE; PRESSURE; PATTERNS; COLD WEATHER; RECRYSTALLIZATION; DIURNAL VARIATIONS; COLORADO; FORESTS; WATER VAPOR; MICROMETEOROLOGY; METAMORPHOSIS; SNOWFIELDS; Ice; permafrost
• Online Access: http://www.dtic.mil/docs/citations/ADA040169; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA040169

Spatial and temporal variations of temperature in alpine snow covers have been systematically observed over a period of two winters. Concurrently, snow crystal metamorphism has been monitored in the same snow covers, along with such basic snow properties as density and ram resistance. Near-surface snow temperatures fluctuate widely in response to diurnal weather variations. Below about 25 cm beneath the surface the temperatures change more slowly in response to longer-term weather trends. Mean snow temperatures are colder on north slopes than south ones but mean snow cover temperature gradients are similar on both exposures owing to shallower snow on south slopes. A forest canopy tends to suppress snow surface radiation cooling and hence reduce magnitude of temperature gradients at depth. Metamorphism in snow follows a recrystallization mode with declining mechanical strength when the saturation water vapor pressure gardient exceeds 0.05 mb/cm. Owing to a nonlinear vapor pressure-temperature relationship over ice, this corresponds to the conventional critical temperature gradient of 0.1 C/cm for this metamorphism mode only at snow temperatures close to the melting point. Mean monthly snow temperature gradients can reasonably be estimated from air temperature and snow depth means, but this method can be extended to vapor pressure gradients only if appropriate corrections for non-linearity are introduced. (Author)