Development of Kyushu University Atmosphere-Ocean General Circulation Model and Research of Climate

本项目的目的是建立九州大学大气-海洋环流模式，研究厄尔尼诺和ENSO等短期气候变化。这个项目的研究采用了两种不同的方法。首先，为了了解海洋-大气耦合动力学的理论背景，采用Anderson-McCreary型海洋模式和Gill型大气模式构建了简化的大气-海洋耦合模型。为了研究厄尔尼诺现象产生的必要条件，进行了多次数值模拟。发现西太平洋的高海洋热含量和西太平洋上空的西风爆发是厄尔尼诺现象产生的必要条件。还进行了一些数值积分来模拟ENSO循环。在这些整合中使用的模型包括一个被陆地包围的有限海洋，模仿太平洋。外部陆地加热我们…更多的太平洋区域被加入来模拟与季风相关的陆地加热。耦合扰动的重复产生与赫斯特（1988）的线性模型以及离赤道的罗斯比波无关。它完全取决于外部陆地加热的幅度。质量预算分析表明，西太平洋纬向风向的变化，由于外部陆地加热与前一次耦合扰动相关的加热之间的相对重要性，调节了与后一次耦合扰动起源相关的海洋热含量。这一机制给出了两个稳定平衡（拉尼娜和厄尔尼诺）之间的振荡，这与Battisti（1988）、Schopf和Suarez（1987）以及Zebiak和Cane（1987）所描述的非常不同。尽管有许多模式的限制，目前的结果似乎与最近对西太平洋海陆空系统的分析是一致的。为了探讨大气季内振荡与海气耦合年际扰动之间可能存在的关系，本文采用海洋-大气耦合模式进行了数值试验。该模式由一个T21大气环流模式和一个简单的海洋模式组成。当海洋以固定的海温保持不动时，在大气中重现季节内振荡。当海洋被活跃的海洋所取代时，由海洋-大气相互作用产生的温暖海洋区域的季内振荡在空间和时间上都变得相当零星。该暖海温区域的平均结构与简单的海-气耦合模式得到的结果非常相似。该模式的耦合扰动具有多尺度结构，同时具有季节内模态和年际模态。少

The objective of this project is to develop the Kyushu University Atmosphere-Ocean general circulation model, and to investigate the short term climatic changes such as El nino and ENSO. The research of this project has been done by two different methods.At first, in order to understand the theoretical background of the coupled ocean-atmosphere dynamics, a simplified atmosphere-ocean coupled model is constructed by using Anderson-McCreary type ocean model and Gill type atmosphere model. Several numerical simulations have been done to investigate the necessary condition for generating the Elnino. It is found that the high oceanic heat content in the westem Pacific and the westerly burst over the western Pacific are the necessary condition for the generation of the El nino. Some numerical integrations have also been done to simulate the ENSO cycle. The model used in these integrations consists of a limited ocean surrounded by lands imitating the Pacific Ocean. An external land heating we … More st of the Pacific is added to simulate the land heating associated with the monsoon. The repetitious generation of the coupled disturbance has nothing to do with the linear model of Hirst (1988) as well as off-equatorial Rossby waves. It is perfectly determined by the amplitude of the external land heating. The mass budget analysis demonstrates that the change of zonal wind direction in the western Pacific, which is due to relative importance between the external land heating and the heating associated with the previous coupled disturbance, modulates the oceanic heat content relevant to the origin of the following coupled disturbance. This mechanism gives the oscillation between two stable equilibria (La Nina and El Nino), which are very different from those described in Battisti (1988), Schopf and Suarez (1987), and Zebiak and Cane (1987). Despite lots of model limitations, the present results seem to be compatible with the recent analyses of the air-sea-land system in the western Pacific.A numerical experiment has been performed using a coupled ocean-atmosphere model in order to examine possible relationships between the atmospheric intraseasonal oscillation and the air-sea coupled interannual disturbance. The model is composed of a T21 atmospheric general circulation model and a simple ocean model. When the ocean is kept motionless with a fixed SST, intraseasonal oscillation is reproduced in the atmosphere. When the ocean is replaced by the active one, the intraseasonal oscillation becomes rather sporadic both in space and time over the warm ocean region produced by the ocean-atmosphere interaction. The mean structure of this warm SST region is very similar to that obtained by the simple coupled ocean-atmosphere model. However, The coupled disturbance in this model has a multi-scale structure having both intraseasonal and interannual modes. Less