松嫩平原北部季节冻土冻融过程及热量传递规律

Freezing Thawing Process and Heat Transfer Law of Seasonal Frozen Soil in the Northern Songnen Plain

为深入了解松嫩平原北部季节冻土冻融过程及热量传递规律,同时为东北寒区工程及寒区农业的土体环境的高效利用提供科学依据。基于松嫩平原北部季节冻土原位监测,开展季节冻土温度变化特性及分层热通量变化规律研究。结果表明:深度小于50 cm土体温度日变化明显,土体温度季节差异随着土体深度增大而减小。2017年3月3日达到最大冻深(164 cm),4月22日为最终融化日期,最终融化深度为130 cm。不同深度土体温度对地表温度响应呈滞后效应,随着土体深度的增加,滞后时间延长;季节冻土在冻融期内浅层土体受到净辐射的影响,热量交换极其频繁;随着土层深度的增加,净辐射的作用减小,热量在土体中传递的损耗增加,热量交换程度减弱,在冻结期,土体损失的热量大于吸收的热量。在整个冻融期内保持负值,冻深线以下土体中的热量持续向上传输,表明160 cm深度以下土体持续对冻土层传递热量。

To provide an in-depth understanding of the freeze-thaw process and heat transfer law of the seasonal frozen soil in the northern part of the Songnen Plain.Meanwhile,it provides scientific basis for the efficient use of soil environment in the cold area engineering and cold area agriculture in northeast China.Based on the in situ monitoring of seasonal frozen soil in the northern part of the Songnen Plain,research on the characteristics of seasonal frozen soil temperature change and the change pattern of stratified heat flux was carried out.The results show that the daily variation of soil temperature at depths less than 50 cm is obvious,and the seasonal difference in soil temperature decreases with increasing soil depth.The maximum freeze depth(164 cm)is reached on March 3,2017,and the final thaw date is April 22,with a final thaw depth of 130 cm.The response of soil temperature to surface temperature at different depths show a hysteresis effect,and the hysteresis time increas with the increase of soil depth.Seasonal frozen soils are subjected to net radiation during the freeze-thaw period and heat exchange is extremely frequent in the shallow soils.As the depth of soil layer increases,the effect of net radiation decreases,the loss of heat transfer in the soil increases,the degree of heat exchange decreases,and during the freezing period,the heat lost from the soil is greater than the heat absorbed.Maintaining negative values throughout the freeze-thaw period,the heat in the soil below the freeze-depth line continues to be transferred upward,indicating that the soil continues to transfer heat to the permafrost layer below 160 cm depth.