NCAR_CLM系列模式对全球近50a陆面状况的模拟及其比较分析

Simulations of global land surface conditions in recent 50 years with three versions of NCAR Community Land Models and their comparative analysis

摘要:

基于普林斯顿大学1948—2006年3 h一次、1°×1°空间分辨率的全球陆面驱动数据,利用NCAR系列陆面模式CLM3.0、CLM3.5、CLM4.0,分别对全球近50 a的陆面状况进行了offline模拟试验。在此基础上,对比分析了不同版本模式对全球土壤温度、土壤湿度、地表感热、潜热和地表径流气候态的模拟结果,揭示了不同版本模式对全球陆面变量模拟的差异及主要特征。结果表明:1)CLM系列模式模拟的土壤温度、湿度在全球范围内存在一定差异。与CLM4.0相比,CLM3.0和CLM3.5模拟的1月、7月的浅层和深层土壤温度在北半球中高纬度存在明显的暖偏差。CLM3.0模拟的土壤湿度在北半球高纬地区均存在不同程度的偏湿,而在热带及中纬度地区则以偏干为主,尤其是对热带地区深层土壤湿度的模拟存在严重偏干的现象;相比之下,CLM3.5模拟的浅层土壤湿度仅在北半球高纬地区存在偏湿的现象;二者对深层土壤湿度的模拟差异较小。2)CLM系列模式模拟的地表能量通量和地表水文变量也存在较明显的差异。模式对潜热通量和感热通量的明显差异主要出现在热带地区,与CLM4.0相比,CLM3.0模拟的潜热(感热)通量总体偏小(大),而CLM3.5模拟的潜热(感热)通量以偏大(小)为主。CLM3.0模拟的地表径流在热带地区明显偏大,CLM3.5在一定程度上改善了上述区域径流偏大的问题,但过分低估了上述地区的地表径流。3)模式模拟结果的差异具有明显的季节变化和区域性特点。总体而言,CLM3.0对不同地区的土壤湿度和冠层蒸散的季节变化模拟都存在较大偏差,其模拟的土壤湿度明显偏低,而对冠层蒸腾作用在冠层蒸散过程中所做的贡献估计不足;CLM3.5和CLM4.0对上述结果有了较明显的改进。对于其他陆面因子的季节变化而言,CLM3.0的模拟能力也存在一定程度的不足,而CLM3.5和CLM4.0的模拟结果则更为合理。

Abstract:

Based on the global 1°×1° and 3-hr atmospheric forcing data from 1948 to 2006 developed at Princeton University,the global land surface conditions in recent 50 years are produced by offline simulation with three different versions of NCAR Community Land Model(i.e.,CLM3.0,CLM3.5 and CLM4.0).Through comparing the simulation results,the differences in simulated soil temperature,soil moisture,latent heat,sensible heat and surface runoff among the three models and the main features are discussed.Results show:1)Differences in the simulated soil temperature and soil moisture are detected among three versions of CLM.Compared to CLM4.0,both CLM3.0 and CLM3.5 show warm bias in the simulated January and July soil temperatures at both shallow and deep layers in the mid-high latitudes of the Northern Hemisphere.The soil moisture simulated by CLM3.0 is too wet in the high latitudes of the Northern Hemisphere,but too dry in the mid-latitudes and the tropics.In contrast,no evident difference is found between CLM3.5 and CLM4.0 except that the soil moisture at shallow layer simulated by CLM3.5 is wetter than that of CLM4.0 in the high latitudes of the Northern Hemisphere.2)Evident differences in the simulated surface energy fluxes and hydrological variables are found among three versions of CLM.Compared to CLM4.0,the differences in the latent heat and sensible heat fluxes simulated by other two models mainly appear in the Tropics.CLM3.0 underestimates(overestimates) the latent heat(sensible heat) fluxes to some extent,while CLM3.5 basically gives larger latent heat flux(smaller sensible heat flux).In addition,the surface runoff simulated by CLM3.0 is evidently overestimated in the tropics,where it is improved but somewhat underestimated by CLM3.5.3)Differences among the model results vary with not only the season but also the selected region.On the whole,CLM3.0 produces larger bias in the simulation of the seasonal cycles of the soil moisture and canopy transpiration over the selected regions,and underestimates the soil moisture and the contribution of canopy transpiration to canopy evapo-transpiration seriously.Such results have been improved in both CLM3.5 and CLM4.0.In case of other land surface variables,CLM3.0 also exhibits some deficiencies,but CLM3.5 and CLM4.0 show better performance.