NCAR/CLM系列陆面模式对内蒙古地表温度的模拟评估

地表温度是影响陆-气之间能量和物质交换的重要地球物理变量,对调节全球气候系统能量循环起着不可或缺的作用。为探讨美国国家大气研究中心(The National Center for Atmospheric Research,NCAR)公共陆面模式(Community Land Model,CLM)对地表温度的模拟能力,利用1948—2004年美国国家环境预报中心(National Centers for Environmental Prediction,NCEP)大气强迫场和NCAR陆面模式CLM3.0、CLM3.5、CLM4.0和CLM4.5对内蒙古地区1981—2004年的地表温度进行off-line模拟,并与观测地面温度资料进行对比。结果表明:NCAR/CLM系列陆面模式模拟地表温度都能较好地再现内蒙古地表温度的时空变化特征,与台站观测有着较好的一致性,其中CLM4.5在内蒙古地区模拟能力最好,与观测的相关系数最高、平均偏差和均方根误差都最小,这主要得益于CLM4.5对粗糙度计算的改进;不同版本CLM模拟地表温度普遍较观测数值偏低,在冬季各版本CLM模拟结果与观测值之间的平均偏差达到最小,在夏季的偏差增大,尤其是在东部地区,夏季偏差3℃以上,说明对最高地表温度的模拟能力东部和中部地区明显低于西部地区;西部地区各个版本差别并不如东部和中部地区明显,这与CLM4.0和CLM4.5改进了雪模式和水文过程有关。综上,CLM4.0和CLM4.5在内蒙古地区有较好的适用性,且模拟值均低于实测地表温度,冬季偏差较小,夏季偏差增大,东部地区偏差大于中部和西部地区。

Simulation and comparative analysis of surface temperature over Inner Mongolia using four NCAR Community Land Models

Surface temperature is an important geophysical parameter in energy and substance exchange processes of land-atmosphere interactions,and is a crucial element of global climate system.Time series of observed surface temperature data from meteorological stations are discrete and lack continuity in space.Satellite retrieval of land surface temperature is continuous in space,but with short time series.The simulation of surface temperatures using land surface models is an effective way of obtaining surface temperature data of high temporal resolutions.However,significant differences have been noted between different versions of land surface models,a large part of which lies in the physical processes of key land surface parameters.Thus a comparative evaluation of the performance of surface temperature for 1981-2004 was conducted over Inner Mongolia in this paper using NCAR (National Center for Atmospheric Research) Land Surface Models (CLM3.0,CLM3.5,CLM4.0 and CLM4.5) forced by NCEP (National Center for Environmental Prediction) and ground observation data.The study compared and analyzed differences in the results between models,tested the capability of models to simulate surface temperature over Inner Mongolia and provided guidance and reference for future improvements in the models.The results of the analysis of temporal and spatial variations in surface temperature over Inner Mongolia showed that:NCAR/CLMs simulations could be used to reproduce spatial and temporal variations that were in good agreement with data observed in ground stations.CLM4.5 model was the best as it had the highest correlation coefficient and lowest average deviation and RMS error for the Inner Mongolia due mainly to improvements in the calculation of roughness in the model.The simulation results for surface temperature by different CLM models were generally lower than the observed values.The mean deviation between the CLM simulated results and the ground observations was minimum during winter.Summer bias increased,especially for the eastern region.The deviation in temperature for the eastern part during summer was above 3 ℃.This indicated that the simulation capability of maximum surface temperature for the eastern and central regions was significantly lower than that for the western region.The differences between various versions of the model for the western region were not as obvious as those for the eastern and central regions.This was related to the improvements in snow patterns and hydrological processes of CLM4.0 and CLM4.5 model versions.In summary,CLM4.0 and CLM4.5 versions were fully applicable in Inner Mongolia,but the simulated values of surface temperature were lower than the measured ones.While the deviations were small in winter and high in summer,the in the eastern region were greater than those in the central and western regions.