基于CLM4.5模式的季节冻土区土壤参数化方案的模拟研究

利用位于季节冻土区的中国科学院那曲高寒气候环境观测研究站那曲/BJ观测点的野外观测数据,通过CLM4.5的单点模拟实验,分析评估了Luo土壤热导率参数化方案、Johansen土壤热导率参数化方案、Coté土壤热导率参数化方案和虚温参数化方案对土壤温、湿度的模拟能力,为将来选取最优的参数及参数化方案来更合理的模拟青藏高原土壤冻融过程为目的的工作提供依据。结果表明:(1)三种土壤热导率参数化方案模拟结果的土壤热传导率有明显差异,其中Coté方案的土壤热传导率最高,Luo方案的土壤热传导率最低。(2)三种热传导率方案均能合理地模拟出土壤温湿度的日变化趋势,Johansen方案对土壤温度年变化趋势模拟的更好,Coté方案对土壤温度模拟的数值较观测值偏离的更小,Luo方案对土壤湿度的模拟更好。(3)加入虚拟温度方程,并引入相变效率参数后,减少了模式对土壤湿度模拟的负偏差,Y-L方案在保持土壤温度较好模拟能力的基础上,能够进一步的提升土壤湿度的模拟能力。

A Simulation Study on Soil Parameterization Scheme of Seasonally Frozen Ground Regions based on CLM4.5

In this paper,the field observation data provided by Naqu station of Plateau Climate and Environment in northern Qinghai-Xizang(Tibetan)Plateau,located in the seasonally frozen ground regions,CLM4.5 is used to analyze and evaluate the simulation ability of thermal conductivity parameterization schemes of Luo,Johansen,and Coté as well as virtual temperature parameterization scheme to calculate soil temperature and humidity,providing basis for the future work of selecting the optimal parameters and parameterization schemes to more reasonably simulate the freeze-thaw process of frozen soil on Tibet Plateau.The results suggested that:(1)The soil thermal conductivity of three parameterization schemes was significantly different,of which the Coté scheme had the highest soil thermal conductivity,while the Luo scheme had the lowest.(2)All the three-soil heat conductivity parameterization schemes can reasonably simulate the daily variation trend of soil temperature and humidity.The Johansen scheme can better simulate the annual variation trend of soil temperature,the Coté scheme has a smaller deviation from the observed value in soil temperature simulation,and Luo scheme has a better simulation on soil moisture.(3)After adding the virtual temperature equation and introducing the phase transition efficiency parameter,the negative deviation of the model for soil moisture simulation is reduced.In addition to maintaining good simulation ability of soil temperature,the Y-L scheme can further improve the simulation ability of soil moisture.