一个大洋环流模式和相应的海气耦合模式的评估Ⅰ.热带太平洋年平均状态

评估了中国科学院大气物理研究所大气科学和地球流体动力学数值模拟国家重点实验室海洋环流模式L30T63和海气耦合模式FGCM-0模拟的热带太平洋年平均状态,资料取自L30T63由观测的大气强迫驱动的Control试验、由NCAR CCM3大气强迫驱动的Spinup试验、以及相应的海气耦合模式FGCM-0.主要的结论是:(1)在"准确"的海表强迫下,Control模拟的海面温度和温跃层与观测结果相当接近,模式的固有误差是赤道冷舌过分西伸和东南太平洋温跃层偏浅.(2)Spinup能模拟出合理的热带太平洋上层海洋环流,但存在两个问题,即:暖池区海面温度显著偏高、沿赤道的梯度过大;赤道温跃层偏浅、东西向坡度偏小,它们分别与CCM3提供的海表短波辐射通量和风应力的系统误差有关.这两个问题很可能是海气耦合模式FGCM-0运行初期误差迅速发展的重要原因.(3)FGCM-0模拟的赤道暖池区上层100 m的平均温度比观测低3℃.分析表明FGCM-0夸大了暖池区海洋动力过程的降温作用,使得模拟的"暖池"在一定程度上具有冷舌的属性.FGCM-0模拟的热带南太平洋温跃层比观测结果偏浅数十米到100 m,以致赤道两侧的上层海洋温度分布趋于对称,成为"double ITCZ"现象在上层海洋中的表现.风应力旋度的系统误差和垂直混合随深度衰减过快是温跃层偏浅的两个可能原因;FGCM-0中与北太平洋中高纬地区深厚冷偏差相关的经圈环流也有利于热带温跃层误差的维持.     

Effect of Ocean Thermal Diffusivity on Global Warming Induced by Increasing Atmospheric CO_2

A global mean ocean model including atmospheric heating, heat capacity of the mixed layer ocean, and vertical thermal diffusivity in the lower ocean, proposed by Cess and Goldenberg (1981), is used in this paper to study the sensitivity of global warming to the vertical diffusivity. The results suggest that the behaviour of upper ocean temperature is mainly determined by the magnitude of upper layer diffusivity and an ocean with a larger diffusivity leads to a less increase of sea surface temperature and a longer time delay for the global warming induced by increasing CO2 than that with smaller one. The global warming relative to four scenarios of CO2 emission assumed by Intergovernmental Panel of Climate Change (IPCC) is also estimated by using the model with two kinds of thermal diffusivities. The result shows that for various combinations of the CO2 emission scenarios and the diffusivities, the oceanic time delay to the global warming varies from 15 years to 70 years.     

大洋温盐环流与气候变率的关系研究:科学界的一个新课题

大洋温盐环流与气候变率的关系研究是90年代中后期以来国际科学界提出的一个新课题。在概述温盐环流基本图像的基础上,讨论了温盐环流在气候系统中的重要作用,介绍了国际科学界针对该问题的未来行动,总结了国际科学界的研究现状。     

一个大气环流模式差分格式的检验

本文用两种工具对我们设计的一个大气环流模式及其差分格式作了较为严格的检验。首先,我们用检验球面模式的传统工具Rossby-Haurwitz波对简化的正压模式进行了检验,其效果与欧洲中心的结果极为一致。其次,我们发展了检验斜压初始方程模式的工具——非线性Haurwitz波,并对环流模式的框架部分作了检验,取得了令人满意的结果。     

球面上斜压原始方程组保持总有效能量守恒的差分格式

本文从标准层结近似下球面上的斜压原始方程组出发,针对两类常用的网格系统——C-网格和B-网格,分别设计出可以保持总动能、总有效位能和总有效表面位能之和守恒的差分格式.同时,讨论了定义在交错网格上的差分和平均算子的一些很有用的性质.     

A Numerical World Ocean General Circulation Model

This paper describes a numerical model of the world ocean based on the fully primitive equations. A "Standard" ocean state is introduced into the equations of the model and the perturbed thermodynamic variables are used in the modlc's calculations. Both a free upper surface and a bottom topography are included in the model and a sigma coordinate is used to normalize the model's vertical component. The model has four unevenly-spaced layers and 4 × 5 horizontal resolution based on C-grid system. The finite-difference scheme of the model is designed to conserve the gross available energy in order to avoid fictitious energy generation or decay.The model has been tested in response to the annual mean surface wind stress, sea level air pressure and sea level air temperature as a preliminary step to its further improvement and its coupling with a global atmospheric general circulation model. Some of results, including currents, temperature and sea surface elevation simulated by the mode! arc presented.     

一个包括地形和非绝热作用的原始方程数值模式

为了模拟大尺度动力过程并改进数值预报,开展了一个原始方程的半球数值模式的研究。 模式的主要特点是:将热力学方程进行改写,整个差分格式保持总能量守恒,但气压梯度项和静力关系的差分格式可以不受任何限制。模式包括地形、摩擦、水平扩散、降水、蒸发和各种非绝热等物理作用。幅射作用直接由导出的微分表达式计算;地面温度由地面热量平衡方程解出而不需要迭代计算。 最后给出这一模式的一次48小时预报个例的试验结果。     

Sensitivity of the upper ocean temperature and circulation in the equatorial Pacific to solar radiation penetration due to phytoplankton

Solar radiation penetration in the upper ocean is strongly modulated by phytoplankton, which impacts the upper ocean temperature structure, especially in the regions abundant with phytoplankton. In the paper, a new solar radiation penetration scheme, based on the concentration of chlorophyll-a, was introduced into the LASG/IAP （State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics） Climate system Ocean Model （LICOM）. By comparing the simulations using this new scheme with those using the old scheme that included the constant e-folding attenuation depths in LICOM, it was found that the sea surface temperature （SST） and circulation in the central and eastern equatorial Pacific were both sensitive to the amount of phytoplankton present. Distinct from other regions, the increase of chlorophyll-a concentration would lead to SST decrease in the central and eastern equatorial Pacific. The higher chlorophyll-a concentration at the equator in comparison to the off-equator regions can enlarge the subsurface temperature gradient, which in turn strengthens the upper current near the equator and induces an enhancing upwelling. The enhancing upwelling can then lead to a decrease in the SST in the central and eastern equatorial Pacific. The results of these two sensitive experiments testify to the fact that the meridional gradient in the chlorophyll-a concentration can result in an enhancement in the upper current and a decrease in the SST, along with the observation that a high chlorophyll-a concentration at the equator is one of the predominant reasons leading to a decrease in the SST. This study points out that these results can be qualitatively different simply because of the choice of the solar radiation penetration schemes for comparison. This can help explain previously reported contradictory conclusions.     

全球水循环的海洋分量研究

利用ＮＣＥＰ／ＮＣＡＲ再分析月平均和逐日资料,采用“余差”方法,计算了１９８４～１９９４年全球海气淡水通量,分析了全球水汽输送的特点。主要结果有：（１）在全球水循环中,副热带大洋是重要的水汽辐散区,热带辐合带、南太平洋辐合带和南太平洋东南海域是集中的水汽辐合区,赤道东风带是夏季印度洋季风环流的主要水汽通道;（２）再现了全球海气淡水通量的分布,例如副热带“海洋沙漠”带、热带辐合带和南太平洋辐合带净降水区等;展示了细节特征,如黑潮区的净蒸发特点等;（３）发现了北大西洋中高纬度地区存在一东北—西南向的净蒸发带,而前人结果中则为净降水带;（４）分析了各大洋海气淡水通量的季节、年际变化特征,讨论了太平洋相对于大西洋作为水汽汇的特点;指出热带辐合带和南太平洋辐合带是海气淡水通量变率最大的海域     

太平洋大尺度环流数值模拟 II:长期平均环流

用本文第Ⅰ部分所给出的四层太平洋环流模式,模拟在定常年平均大气强迫场驱动下太平洋长期平均环流。所进行的53年数值积分表明,模式成功地模拟出观测到的太平洋大尺度环流基本特征,特别是能直接计算出在海洋动力学和大尺度海气相互作用研究中有重要应用的海面起伏,对表层流场的模拟也明显优于具有同等分辨率的其他模式的结果;对气候有重要影响的SST形势的模拟结果同观测也较为一致。本文还用第53年数值积分资料进行了扰动压力场、斜压扰动压力场和海表热通量等的诊断计算和分析。文中还对模拟结果进行了物理和动力学的分析和解释。