LASG/IAP大气环流谱模式对陆面过程的敏感性试验

The Sensitivity of the Spectral Atmospheric General Circulation Model of LASG/IAP to the Land Process

将中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室最近发展的高分辨率全球大气环流谱模式SAMIL-R42L26,分别与两个陆面模式———NCAR通用陆面模式CLM和简化的简单生物圈模式SSiB进行耦合。在比较了两个陆面过程模式,指出CLM改进方面的基础上,通过分析两个陆气耦合模式所模拟的陆气通量交换结果,指出新版本的陆气耦合模式(SAMIL-R42L26与CLM耦合)对表面感热、温度、降水率、潜热通量和海平面气压场的模拟能力大大提高,尤其对于夏季表面感热通量场,使亚洲北部和东南部、格陵兰岛以及北美洲大部分地区的数值从100 W/m2降低到接近60 W/m2,与NCEP再分析资料一致。新版本的陆气耦合模式模拟陆地表面能量收支趋于平衡,为下一步发展海-陆-气-冰耦合气候系统模式提供保障。采用CLM陆面模式,SAMIL-R42L26能较好地模拟亚洲季风区地表感热和潜热的季节演变趋势,而采用SSiB陆面模式的结果,则存在较大误差。文中的结果表明,不同的陆面模式所模拟的大气下垫面(包括洋面)通量发生的变化,通过陆气耦合过程产生的影响不仅仅是局地性的,而且是全球范围的。

The new version of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics （LASG/IAP） general circulation model （R42L26） is coupled with National Center for Atmospheric Research Community Land Model （NCAR CLM） and the Simplified Simple Biosphere （SSiB） model, respectively. The comparison of these two different kinds of land surface schemes indicates that there are certain improvements in CLM, including the land surface is represented by five primary subgrid land cover types in each grid cell; the vegetated portion of a grid cell is further divided into patches of 4 - 16 plant functional types; the relative area of each subgrid unit, the plant functional type, and leaf area index are obtained from 1 km satellite data; the soil texture dataset allows vertical profiles of sand and clay. Most of the physical parameterizations in the model have also been updated： 10 layers for soil temperature and soil water; a multilayer snowpack; runoff based on the TOPMODEL concept; new formulation of ground and vegetation fluxes; and vertical root profiles from a global synthesis of ecological studies. Thus, the veracity of soil moisture and surface albedo has been improved greatly. By analyzing the simulated land atmosphere flux in these two versions of coupled models, it is found that the land surface energy budget tends to be balanced in the new version of land-atmosphere coupled model （SAMIL-R42L26 coupled with CLM）, which provides the most important guarantee for the next generation of the ocean-land-atmosphere coupled model, while there is the virtual energy source, which is about 2 W/m^2 , in the old version （SAMIL-R42L26 coupled with SSiB）. Moreover, the performances of the new version land-atmos phere coupled model are greatly improved in the simulation of the surface temperature, precipitation rate, surface latent heat flux, sea-level pressure and most notable surface sensible heat flux, which is reduced from more than 100 W/m^2 to nearly 60 W/m^2 in the broad region of north and southeast Asia, Greenland and North America, which is consistent well with NCEP reanalysis data. Due to the increase of simulated surface albedo and soil moisture, the surface temperature is reduced about 10℃ in Antarctica and Greenland, which more approach the observation. Compared with the version coupled with SSiB land surface model, SAMIL-R42L26 coupled with CLM also has better performance in simulating the seasonal evolution of the surface sensitive heating and latent heating in Asian monsoon region, the results are very close to reanalysis data. Base on the different simulation between these two different kinds of land surface schemes, it is implied that the effect of land-atmosphere coupled process is not only in local re gion but also in global scale.