考虑冻融锋面移动过程的多年冻土水热模拟  

Modeling permafrost hydrothermal features consideringthe movement of freeze-thaw front

作　　者：肖敏轩 赵林 张钰鑫 高骏强 邹德富 胡国杰 赵建婷 李智斌 赵拥华 肖瑶 刘广岳 杜二计 刘淼 XIAO Minxuan;ZHAO Lin;ZHANG Yuxin;GAO Junqiang;ZOU Defu;HU Guojie;ZHAO Jianting;LI Zhibin;ZHAO Yonghua;XIAO Yao;LIU Guangyue;DU Erji;LIU Miao(School of Geographical Sciences,Nanjing University of Information Science&Technology,Nanjing 210044,China;Cryosphere Research Station on the Qinghai-Tibet Plateau,State Key Laboratory of Cryospheric Science,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China;School of Mathematics and Statistics,Nanjing University of Information Science&Technology,Nanjing 210044,China)

机构地区：[1]南京信息工程大学地理科学学院,江苏南京210044 [2]中国科学院西北生态环境资源研究院冰冻圈科学国家重点实验室藏北高原冰冻圈特殊环境与灾害国家野外科学观测研究站,甘肃兰州730000 [3]南京信息工程大学数学与统计学院,江苏南京210044

出　　处：《冰川冻土》2024年第1期13-27,共15页Journal of Glaciology and Geocryology

基　　金：第二次青藏高原综合科学考察研究项目(2019QZKK0201);青藏高原自然资源要素综合观测试点项目(DD20208064);江苏省基础研究计划青年基金项目(BK20200828)资助。

摘　　要：活动层内部的冻融锋面是冻融过程中冻结土层与融化土层的分界面,其上下土层的水热参数有着显著差异。在陆面过程模式中准确描述冻融锋面的移动过程将有助于提高其对多年冻土水热过程的模拟能力。本研究首先将Noah-MP陆面过程模式的模拟深度扩展到20 m,并将原模式的4层土层增加到19层土层,同时引入前人的有机质方案和植被根系方案,然后在此基础上,通过耦合Stefan方法以加强模式对冻融锋面的模拟能力,进而探究耦合Stefan方法的Noah-MP模式对西大滩多年冻土站点水热过程的模拟效果。研究中设置了不耦合Stefan方法的CTL控制试验和耦合Stefan方法的STE对照试验来分别模拟西大滩多年冻土站点2012年0~20 m的土壤温度与土壤液态含水量,模拟结果用站点0~3.2 m内10个深度的日均土壤温度、土壤液态水含量监测数据以及3 m、6 m和10 m的年均地温监测数据来做验证。研究结果表明,由土壤温度模拟值插值得到的冻融锋面(0℃等温线)有明显阶梯状特征,最大冻融深度与实测相比偏大。耦合Stefan方法增强了Noah-MP模式模拟冻融锋面的能力,使得模式能够基于Stefan方法较好地模拟出冻融锋面的变化趋势和最大深度。同时,改进后的模式整体改善了对土壤温度的模拟效果,使得0~3.2 m各土层土壤温度的平均RMSE降至0.89℃,减小44%;平均MBE降至-0.13℃,减小86%;模拟的3~20 m年均地温与实测数据更为接近。改进后的模式对土壤液态含水量的模拟水平也有一定改善,其中,模拟的0~3.2 m各土层的土壤液态含水量的平均RMSE降至0.06 m^(3)·m^(-3),减小33%;平均MBE降至-0.01 m^(3)·m^(-3),减小67%。模式还较好描述了活动层20 cm、40 cm、80 cm、120 cm土壤的融化时间。可以看出,在陆面过程模式中耦合能够较好模拟冻融锋面移动过程的Stefan方法可较大程度提高模式的模拟能力,是陆面过程模式改进的有效途�The freeze-thaw front within active layer is the interface between the frozen and the unfrozen soil lay-ers during the freeze-thaw process,and the hydrothermal parameters of the soil layers on both sides of freeze-thaw front are significantly different.Therefore,the accurate simulation of the freeze-thaw front movement in the land surface model is essential to improve models both in simulating the hydrothermal characteristics of per-mafrost and simulating the energy-water balance of the land surface.In this study,the simulation depth of the Noah-MP land surface model was extended to 20 m,and the 4 soil layers of the Noah-MP land surface model was increased to 19 soil layers,and the organic matter scheme and vegetation root scheme were introduced.Af-ter these modifications,in order to strengthen the ability of the Noah-MP land surface model on simulating freeze-thaw front,the Stefan method was coupled.Then,the simulation effect of the augmented Noah-MP land surface model on the hydrothermal process of the Xidatan permafrost site was evaluated.Two experiments,CTL experiment(coupled Stefan method)and STE experiment(not coupled Stefan method),were conducted to sim-ulate the soil temperature and soil liquid water content of 0~20 m in 2012,and the simulation results were veri-fied by the observed daily soil temperature and soil liquid water of 0~3.2 m and the observed yearly ground tem-perature of 3 m,6 m and 10 m.The results showed that the freeze-thaw front(0°C isotherm)obtained by inter-polation of soil temperature simulation values had obvious step-like characteristics,and its maximum freeze-thaw depth was larger than the measured.Coupling Stefan method enhanced the ability of Noah-MP model to simulate the freeze-thaw front,so that the model was able to better simulate the change trend and maximum depth of the freeze-thaw front.At the same time,coupling Stefan method also improved the simulation of soil temperature.The mean RMSE and the mean MBE of the soil temperature in the soil layers of 0~3.2 m decreased to 0.

关 键 词：Stefan方法 冻融锋面 Noah-MP 陆面过程模式 西大滩 

分 类 号：P642.14[天文地球—工程地质学]