The Structure and Composition of the Annular Modes in an Aquaplanet General Circulation Model
The Structure and Composition of the Annular Modes in an Aquaplanet General Circulation Model
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水行星大气环流模型中环形模态的结构和组成
DOI：
10.1175/1520-0469(2002)059
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
G. Vallis
中科院分区：
文献类型：
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作者：
B. Cash;P. Kushner;G. Vallis
本文研究了一个具有纬向对称下边界的大气环流模式模拟的环形模态。环形模态被定义为纬向平均地面气压的主要经验正交函数（Experimental Orthogonal Function，缩写为ERF），具有由南北偶极子组成的正交结构，与观测结果相似。地面气压纬向变化的主导波具有相同的纬向结构，也是纬向对称的。由于下边界是纬向对称的，合成的天与高投影到模式，在抽样误差范围内，没有纬向结构。然而，在此期间的zonalmean表面压力项目强烈的环形模式的个别时期是由zonally本地化的结构为主。因此，模式环形模式代表了纬向局部事件的纬向均匀分布，具有类似的纬向结构，而不是纬向对称的变化模式本身。个别的环状模事件通常表现为南北遥相关模式，其纬向结构与环状模非常相似，纬向结构在经度上延伸608到908，其作用中心之间有轻微的西北-东南偏移。类似的结构被发现的EOFs计算超过一个子集的域对应的大西洋盆地的宽度。的遥相关型和区域EOF的空间结构类似于观测到的北大西洋涛动（NAO）模式。
The annular mode simulated by an atmospheric general circulation model with a zonally symmetric lower boundary is investigated. The annular mode, defined as the leading empirical orthogonal function (EOF) of the zonal-mean surface pressure, has a meridional structure consisting of a north‐south dipole, similar to observations. The leading EOF of the zonally varying surface pressure has the same meridional structure and is also zonally symmetric. Because the lower boundary is zonally symmetric, composites of days with high projection onto the mode have, to within sampling error, no zonal structure. However, individual periods during which the zonalmean surface pressure projects strongly onto the annular mode are dominated by zonally localized structures. Thus, the model annular mode represents a zonally homogeneous distribution of zonally localized events with a similar meridional structure, rather than a zonally symmetric mode of variability per se. Individual annularmode events typically show a north‐south teleconnection pattern whose meridional structure closely resembles the annular mode and whose zonal structure extends 608 to 908 in longitude, with a slight northwest‐southeast offset between its centers of action. Similar structures are found for EOFs calculated over a subset of the domain corresponding to the width of the Atlantic basin. The spatial structure of both the teleconnection pattern and the regional EOFs resemble the observed North Atlantic Oscillation (NAO) pattern.