陆面过程对气候影响的数值模拟:SSiB与IAP/LASG L9R15 AGCM耦合及其模式性能

利用陆面过程模式 SSi B与 IAP/LASG发展的 L9R1 5AGCM的耦合 1 0 a积分试验 ,研究了全球尺度大气与地表的水分和能量交换以及陆地与大气环流和气候的相互作用。模拟表明 :SSi B模式可模拟出陆地上较为真实的表面通量及其日变化 ,较好地定量描述土壤 -植被 -大气连续体系 ( SPAC)中能量和水分的传输过程。因此 ,将其引入气候模式中能够模拟出比 CTL- AGCM更合理的气候平均状态、水汽分布以及水汽输送的气候特征 ,特别是亚洲夏季风水汽输送独特的地域性 ,再现了大气环流 ,尤其是陆面气候的基本特征。并指出 ,陆面过程参数化的引进及其陆面状况的变化显著地改善了全球陆地上的水分平衡状况。利用改进的再循环降水模式 ,进一步研究了陆面过程参数化明显改进降水模拟的物理机制。指出全球陆地 ,特别是盛夏北半球干旱、半干旱地区的再循环降水率明显减小 ,与陆面上表面潜热通量的显著减小区一致 ,从而克服了许多未耦合陆面过程的 AGCMs因对地表水过程非常简单地参数化导致的普遍存在着整个陆地降水偏高 ,改善了全球陆地上的水分平衡状况。因此 ,在充分耦合的陆气环流模式中模拟的降水分布与实况接近。

NUMERICAL SIMULATIONS OF EFFECTS OF LAND SURFA-CE PROCESSES ON CLIMATE:IMPLEMENTING OF SSIB IN IAP/LASG AGCM L9R15 AND ITS PERFORMANCE

This is an investigation of exchanges of energy and water between continents and the atmosphere . The Simplified Simple Biosphere (SSiB) model developed by Xue et al.(1991) was designed to explore the impact of and mechanisms of land surface atmosphere interactions on hydrological cycle and general circulation by implemented in a modified version of IAP/LASG global spectral general model (L9R15 AGCM). The results of comparing the monthly simulations of AGCM with and without SSiB show that SSiB can produce a better partitioning of the land surface fluxes of heat and moisture and its diurnal variations. It also gives the transport of energy and water among atmosphere, vegetation and soil processes explicitly and realistically. So the coupled SSiB AGCM runs lead to most conspicuous improvements of the simulated circulation,precipitation climatology as well as mean water vapor content and its transport, particularly in the Asian monsoon region in the real world than CTL AGCM. It is also pointed out that both the implementation of land processes parameterization and the variations in land surface into the GOALS model improve hydrological balance over continents greatly and have a significant impact on the simulated climate. Improved precipitation recycling model was employed to verify the impact of and mechanisms of land surface hydrology parameterization for atmospheric general circulation model on hydrological cycle and precipitation climatology. It is shown that as a consequence of reduced evapotranspiration over all land, particularly in the arid and semi arid region during the Northern Hemisphere summer, the recycling precipitation rate is significantly reduced. Therefore the coupled SSiB AGCM runs reduced the bias of too much precipitation over land surface in most AGCMs and much improved in the simulated precipitation over land in many regions of the world than CTL AGCM.