Variations of Snow Temperature and Their Influence on Snow Cover Physical Parameters in the Western Tianshan Mountains

Snow cover is a dynamic and open energy balance system. Temperature is the basic factor in snow metamorphism, and during this process the snow crystal particles lose their positions in the crystal lattice. The temperature gradient within the snow cover caused by uneven temperature distribution, is a key feature that controls heat and mass transfer, moisture migration, and growth of snow crystals.

Previous studies showed that researches on heat migration during snowmelt are becoming more important, but all those models lack of intensive study of internal temperature fluctuation within the snow layer, especially simple equations related to snow depth. Therefore, Prof. WEI Wenshou and his research team attempt to build a simple model of internal temperature fluctuations to provide foundation for studying snow cover thermo-physics and energy balance. Automatic temperature recorders were used to sample at 10-minute intervals at the Tianshan Station for Snowcover & Avalanche Research, CAS. 10-layer snow temperature and the snow cover parameters were measured by the snow property analyzer (Snow Fork) in its Stable period, Interim period and Snow melting period.

Results indicate that the amplitude of the diurnal fluctuation in the temperature during Snow melting period is 1.62 times greater than that during Stable period. Time up to the peak temperature at the snow surface lags behind the peak solar radiation by more than 2.5 hours, and lags behind the peak atmospheric temperature by more than 0.2 hours during all three periods. The optimal fitted function of snow temperature profile becomes more complicated from Stable period to Snow melting period. 22 h temperature profiles in Stable period are the optimal fitted by cubic polynomial equation. In Interim period and Snow melting period, temperature profiles are optimal fitted by exponential equation between sunset and sunrise, and by Fourier function when solar radiation is strong. The vertical gradient in the snow temperature reaches its maximum value at the snow surface for three periods. The peak of this maximum value occurs during Stable period, and is 4.46 times greater than during Interim period. The absolute value of temperature gradient is lower than 0.1°C cm-1 for 30 cm beneath snow surface. Snow temperature and temperature gradient in Stable period~Interim period indirectly cause increase (decrease) of snow density mainly by increasing (decreasing) permittivity. While it dramatically increases its water content to change its permittivity and snow density in Snow melting period.

The result has been published on Journal of Mountain Science, 2011, 8(6): 827-837. This paper is also archived at http://www.springerlink.com/content/uv0708x2xt30155j/.