陆面模式CLM4.5对青藏高原高寒草甸地表能量交换模拟性能的评估

Evaluation of the Surface Energy Exchange Simulations of Land Surface Model CLM4.5 in Alpine Meadow over the Qinghai-Xizang Plateau

利用中国科学院那曲高寒气候环境观测研究站2013年9月1日至2014年8月31日一个完整年的观测资料,对陆面过程模式CLM4.5在青藏高原(下称高原)高寒草甸下垫面地表能量交换的模拟性能进行了评估。模拟结果表明,CLM4.5能够较好的模拟高原春季、夏季和秋季非冻结期地面长波、反射辐射和地表净辐射、感热和潜热通量以及地表土壤热通量等的季节变化和日循环特征。但对冬季冻结期地表温度的模拟偏低,导致模拟与观测的感热反相,对地面反射辐射模拟偏大。截断冬季降水的敏感性试验进一步指出,模式冬季反射辐射偏大主要是由于积雪引起的地表反照率偏高造成,进而造成地表温度以及感热通量的模拟偏低。因此,高原积雪参数化方案以及与积雪相关的反照率参数化方案还需进一步改进和完善。

Driven by a full year observations from 1 September 2013 to 31 August 2014 of Nagqu Climatic and Environmental observation station in the Qinghai-Xizang Plateau,the land surface model CLM 4. 5 is used to evaluate its performance in simulating the surface energy exchange in the alpine meadowover the Qinghai-Xizang Plateau. Results indicate that CLM 4. 5 can reproduce the characteristics of seasonal variation and diurnal cycle of the surface longwave radiation,reflected radiation,net radiation,sensible latent heat flux and soil heat flux in spring,summer and fall when the soil does not freeze completely. However,the model underestimates the surface temperature in winter,which leads the reverse of sensible heat flux between simulations and observations during this period,while overestimates the reflected radiation. Results from the sensitive test further demonstrate that the overestimation of surface albedo can lead to the overestimation of reflected radiation in winter,causing the underestimation of surface temperature and the sensible heat flux. Consequently,the parameterization schemes of snowprocesses and surface albedos in CLM 4. 5 need to be further improved.