人工冻土观测的冻点对应的土壤温度研究

Analysis of the soil temperature corresponding to the frozen point based on manual frozen soil observation

基于2018年12月至2020年3月喀左、沈阳、辽阳、满洲里4个国家级地面气象站人工冻土器与测温式冻土自动观测仪观测的资料,对人工冻土观测获得的冻点与测温式冻土自动观测仪获得的相应深度的温度进行对比分析。结果表明:人工冻土器获取的冻点对应的土壤温度与0℃总体一致,又不完全重合;0—35 cm深度范围,冻点对应的温度变化范围为-2~6℃,呈现跳跃性变化。35 cm以下深度范围,冻土冻点对应的温度变化范围为-0.5~1.0℃;融化过程冻点对应的平均温度高于冻结过程冻点对应的平均温度。从完全融化时间上来看,人工冻土器观测到的完全融化时间晚于测温式冻土仪0℃线完全消失的时间。人工冻土观测的实质是获得土壤温度0℃点所在位置。灌注不同台站水的冻土器内管在相同的温度环境下,冻结与融化状态无明显区别;人工冻土器内管冻结过程是温度和持续时间双重作用的结果,深层土壤温度变化缓慢,使得内管中的水冻结和融化需要的时间长。另外,作为接触式测温设备,减小外因产生的时滞是提高其灵敏度的重要环节,建议测温式冻土仪的外管壁使用温度滞后效应更小的金属外管。

Based on the data observed with the manual frozen soil apparatus(MFSA)and the temperature-measuring automatic frozen soil apparatus(TMMFSA)from December 2018 to March 2020 at four national surface meteorological stations i.e.Kazuo,Shenyang,Liaoyang,and Manzhouli,the freezing point obtained from MFSA and soil temperature measured with TMMFSA were compared.The results show that the freezing point temperature from MFSA was generally consistent with 0℃with some small differences.At 0-35 cm soil depth,soil temperature corresponding to the freezing point was between-2 to 6℃with a jumping change.Below 35 cm soil depth,soil temperature corresponding to the freezing point ranged from-0.5 to 1℃,and the mean temperature corresponding to the freezing point in the melting process was higher than that in the freezing process.The completely melting time observed with MFSA was later than that when the 0℃lines observed by TMMFSA disappeared completely.The essence of artificially frozen soil observation is to obtain the position of soil temperature of 0℃.Under the same temperature conditions,there is no obvious difference between freezing and melting state in the inner pipe of the frozen soil observation instrument filled with water from different stations.The freezing process of the inner pipe of MFSA was closely related to the temperature and duration of the persistent freezing.Specifically,slow change of soil temperature in the deep layer causes the increase of duration of freezing and melting of water in the pipe.As a contact temperature measuring device,reducing the time delay caused by external reasons is very important to improve its sensitivity.It is suggested that the metal outer tube with less temperature lag effect should be used in TMMFSA,and the soil temperature with high spatio-temporal resolution obtained by TMMFSA should be applied to business.More importantly,soil temperature data measured by TMMFSA can provide sufficient data to support the study of the characteristics of soil temperature change and the heat exchange between soil and atmosphere.