Variations of Snow Temperature and their Influence on Snow Cover Physical Parameters in the Western Tianshan Mountains,China

This article discussed about snow temperature variations and their impact on snow cover parameters.Automatic temperature recorders were used to sample at 10-minute intervals at the Tianshan Station for Snow-cover and Avalanche Research,Chinese Academy of Sciences.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.