黄河源区不同降雪年土壤冻融过程及其水热分布对比分析

利用黄河源区鄂陵湖西侧野外观测站一个多雪年和一个少雪年的数据,对多雪年和少雪年土壤冻融过程及水热分布进行了对比分析。结果表明:黄河源区多雪年积雪集中时段1—3月气温明显偏低,分别比少雪年低3.04℃、3.15℃、3.58℃。多雪年1—3月地气间热交换明显弱于少雪年,且多雪年土壤由热源转为热汇的时间晚于少雪年。多雪年1月土壤净输出的热量少于少雪年1月,多雪年2—3月土壤净输出的热量多于少雪年2—3月,导致多雪年1月土壤温度高于少雪年各土层,而2—3月土壤温度明显低于少雪年,且多雪年1—3月土壤升温速度慢于少雪年,使得多雪年5~40 cm各土层土壤消融初日比少雪年分别晚24 d、23 d、11 d和12 d,从而导致多雪年土壤湿度增加晚于少雪年。

Soil Freezing-thawing Process and Its Temperature and Moisture Conditions in High and Low Snowfall Years in Headwaters of the Yellow River

Based on the observational data in headwaters of the Yellow River,this paper analyzed the soil freezing-thawing process and its temperature-moisture conditions in high and low snowfall years.The results showed that the values of monthly air temperature in January,February and March in high snowfall year were 3.04 ℃,3.15 ℃ and 3.58 ℃ lower than those in low snowfall year,respectively.The ground-air heat exchange in high snowfall year was weaker than that in low snowfall year,and the time when soil turned from heat source to heat sink in high snowfall year was later than that in low snowfall year.The lost heat of soil in January in high snowfall year was less than that in low snowfall year but more in February and March.As a result,soil temperature in January in high snowfall year was higher than that in low snowfall year,it in February and March in high snowfall year,however,was obviously lower than that in low snowfall year.Soil temperature increase during the period from January to March in high snowfall year was slower than that in low snowfall year,which caused the beginning dates of soil thawing were 24,23,11 and 12 days later in high snowfall year than that in low snowfall year,respectively.Therefore,the increase of soil moisture content started earlier in low snowfall year than that in high snowfall year.