中国东北地区季节性积雪导热系数及温度变化特征分析

积雪作为一种重要的下垫面,其热力学性质对周围环境的影响至关重要。利用中国东北地区天然积雪在不同密度(0.30、0.35、0.40、0.45 g/cm^3)下的雪温数据,分析积雪温度的变化特征,研究不同温度(-5、-10、-15、-20、-25℃)、不同密度(0.35、0.40、0.45、0.50、0.55、0.60 g/cm^3)下的积雪导热系数变化规律。结果表明:雪的导热系数随密度的增加而逐渐增大,二者之间存在良好的指数相关关系;在不同密度下雪导热系数对温度的响应呈现明显的差异,密度为0.40~0.45 g/cm^3时,导热系数随温度的升高而增大,密度为0.50~0.60 g/cm^3时,温度在-15~-25℃的雪导热系数随温度的降低而增大;在温度观测期间,雪温与气温变化趋势一致,且均低于0℃,在一天的不同时段,表面雪层会出现冷暖中心,0~20 cm浅层雪层的温度变化剧烈,雪温变化幅度自雪面向下逐渐减小,雪温振幅与积雪深度之间存在良好的负指数相关关系。深层雪温达到极值的时间滞后于表面雪层约4 h。在相同深度的雪层中,雪层温度随密度的增加呈现减小的趋势。

Analysis of Thermal Conductivity and Temperature Variation Characteristics of Seasonal Snow in Northeast China

As an important underlying surface,the thermal properties of snow are extremely important to the surrounding environment.Based on the snow temperature data under different densities(0.30 g/cm^3,0.35 g/cm^3,0.40 g/cm^3 and 0.45 g/cm^3)of natural snow in Northeast China,the variation characteristics of snow temperature were analyzed.At the same time,the variation law of the thermal conductivity of snow at different temperatures(-5℃,-10℃,-15℃,-20℃and-25℃)and densities(0.35 g/cm^3,0.40 g/cm^3,0.45 g/cm^3,0.50 g/cm^3,0.55 g/cm^3 and 0.60 g/cm^3)was analyzed.The results showed that the thermal conductivity of snow was increased with the increase of density,and there was a great index correlation between them.And the response of the thermal conductivity of snow in temperature showed obvious difference under different densities.In the density range of 0.40~0.45 g/cm^3,the thermal conductivity was increased with the increase of temperature;in the density range of 0.50~0.60 g/cm^3 and the temperature range of-15~-25℃,the thermal conductivity of snow was increased with the decrease of temperature;during the temperature observation period,snow cover temperature was consistent with the change trend of air temperature,and both were less than 0℃.In different periods of the day,the surface of the snow layer appeared to the cold and warm center,and the temperature of the shallow 0~20 cm snow layer was changed dramatically.The variation range of snow temperature was gradually decreased with the increase of snow depth.There was a great negative index correlation between amplitude of snow temperature and snow depth.The time of reaching the extreme value of deep snow temperature was slightly lagged behind that of the surface snow layer about 4 h.In the same depth of the snow layer,the temperature was decreased with the increase of density.