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Advances in Meteorology
Volume 2016, Article ID 9476098, 15 pages
http://dx.doi.org/10.1155/2016/9476098
Research Article

A Simulation and Validation of CLM during Freeze-Thaw on the Tibetan Plateau

1Key Laboratory of Land Surface Process and Climate Change in Cold and Arid Regions, Cold and Arid Regions Environment Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China
2University of the Chinese Academy of Sciences, Beijing 100049, China
3Chengdu University of Information Technology, Chengdu 610225, China
4Changzhou Meteorological Administration, Changzhou 213000, China

Received 21 December 2015; Revised 7 March 2016; Accepted 12 April 2016

Academic Editor: Xiao-Ming Hu

Copyright © 2016 Xuewei Fang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The applicability of a new soil hydraulic property of frozen soil scheme applied in Community Land Model 4.5 (CLM4.5), in conjunction with an impedance factor for the presence of soil ice, was validated through two offline numerical simulations conducted at Madoi (GS) and Zoige (ZS) on the Tibetan Plateau (TP). Sensitivity analysis was conducted via replacing the new soil hydraulic property scheme in CLM4.5 by the old one, using default CLM4.5 runs as reference. Results indicated that the new parameterization scheme ameliorated the surface dry biases at ZS but enlarged the wet biases which existed at GS site due to ignoring the gravel effect. The wetter surface condition in CLM4.5 also leads to a warmer surface soil temperature because of the greater heat capacity of liquid water. In addition, the combined impact of new soil hydraulic property schemes and the ice impedance function on the simulated soil moisture lead to the more reasonable simulation of the starting dates of freeze-thaw cycle, especially at the thawing stage. The improvements also lead to the more reasonable turbulent fluxes simulations. Meanwhile, the decreased snow cover fraction in CLM4.5 resulted in a lower albedo, which tended to increase net surface radiation compared to previous versions. Further optimizing is needed to take the gravel into account in the numerical description of thermal-hydrological interactions.