Large‐scale motion in the Great Lakes
Large‐scale motion in the Great Lakes
复制标题
五大湖的大规模运动
DOI：
10.1029/jz072i016p04151
复制
发表时间：
1967
影响因子：
--
通讯作者：
G. Csanady
中科院分区：
文献类型：
--
作者：
G. Csanady
五大湖的大尺度运动可以假定为小Rossby数，从而使运动方程线性化，同时可以忽略科里奥利参数随纬度的变化。当应用到一个两层的湖泊模型，方程成为相同的方程在湖泊中的表面和内部的假潮的行为，但现在的“电流”，以及“波”的解决方案，这些方程成为兴趣。水平方向上的四个运动方程（假设静水压力在垂直方向上的分布）和两个连续性方程可以简化为两组独立的方程，分别对应于主要的“内部”和“表面”模态。这些每个的解决方案包括一个固定的模式，可能是一些非常缓慢的周期性模式类似于开尔文波（但只有当盆地足够大）和一些更快的周期性模式对应于表面和内部的假潮旋转的盆地。当应用于圆形盆地时，恒定深度的“模型大湖”（适合于五大湖的尺度和其他特征）该理论认为：（1）夏季层结期间存在斜压“海岸急流”;（2）周期为半摆日许多倍的缓慢逆时针旋转内波;以及（3）表面和内部假潮，其在任一方向上旋转，并且具有至多几个小时的周期（表面模式）或至多在惯性周期的一小部分内（内部模式）。对现有观测材料的研究确实表明，这些特征在五大湖中是可以探测到的。
Large-scale motion in the Great Lakes can be assumed to be of small Rossby number, so that the equations of motion can be linearized and at the same time the variation of the Coriolis parameter with latitude can be neglected. When applied to a two-layer lake model, the equations become identical with the equations governing the behavior of surface and internal seiches in lakes, but now ‘current-like,’ as well as ‘wave-like’ solutions to these equations become of interest. The four equations of motion in the horizontal (assuming hydrostatic pressure distribution in the vertical) and the two continuity equations can be reduced to two independent sets of equations for the principal ‘internal’ and ‘surface’ modes. The solutions of each of these comprise one stationary mode, possibly some very slow periodic modes akin to Kelvin waves (but only if the basin is large enough) and some faster periodic modes corresponding to surface and internal seiches which rotate around the basin. When applied to a circular basin, constant depth ‘model Great Lake’ (of dimensions and other characteristics appropriate to the Great Lakes) the theory suggests the existence of (1) baroclinic ‘coastal jets’ during the summer stratification; (2) slow counterclockwise rotating internal waves of a period many times the half-pendulum day; and (3) surface and internal seiches rotating in either direction and having a period of at most several hours (surface modes) or up to within a small fraction of the inertial period (internal modes). An examination of the available observational material indeed suggests that these features are detectable in the Great Lakes.