Spatial and Temporal Distributions of Snow Temperature in Forest of the Western Tianshan Mountains,China

The snow temperature under Picea schrenkiana forest crown and on the open ground was observed at Tianshan Research Station for Snow-cover and Avalanche of the Chinese Academy of Sciences from Dec 27,2009 to Apr 2,2010.The spatial and temporal distributions as well as variations of snow temperature were analyzed in details.The results indicated that there is a higher snow temperature near the ground surface,and local cold and warm centre happen at the snow surface layer.The snow temperature under crown is higher than that on the open ground in stable period,which present a contrary trend in snowmelt period;the low and high temperature centre of forest snow appears later and weaker than that on the open ground.Besides,the decreasing rate of snow temperature amplitude with depth and time under crown is lower than that on the open ground above break point,but there is no statistical difference below break point at early stable period.The snow temperature gradient is small and positive,and it increases with air temperature decreasing but decreases with depth from surface down.The negative temperature gradient of forest snow appeases later than that on the open ground.Under crown and on the open ground,the maximum positive temperature gradient of snow reaches 0.95℃/cm and 0.82℃/cm,and the negative temperature gradient reaches-0.84℃/cm and-0.35℃/cm,respectively.Whereas the whole layer snow temperature gradient under forest crown is larger than that on the open ground.