Advection and eddy mixing in the Mediterranean salt tongue
Advection and eddy mixing in the Mediterranean salt tongue
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地中海盐舌中的平流和涡流混合
DOI：
10.1357/0022240933223882
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发表时间：
1993
影响因子：
0.5
通讯作者：
J. Price
中科院分区：
文献类型：
--
作者：
M. Spall;P. Richardson;J. Price
拉格朗日轨迹被用来估计地中海盐舌附近的低频变率和混合。观测到了拉格朗日变率的两种主要形式：(1)近纬向低频运动和(2)西北向东南方向的波状振荡。金丝雀盆地盐舌中心附近存在纬向运动，而南侧和东侧则普遍存在振荡。结果表明，纬向运动是大尺度气流斜压不稳定的结果。它们在纬向上增强了低频变率(周期大于200天)和近各向同性中尺度变率(周期50至200天)。这些波动被认为是在佛得角前锋区向南产生的斜压Rossby波的特征。它们在中尺度带上有很强的峰值，并且具有基本各向同性的低频分量。纬向运动的积分时间尺度较长(纬向和经向分别为23天和13天)，而波动的积分时间尺度较短(7.7天和5.0天)。由此产生的涡旋扩散系数是各向同性和非均匀的，在盐舌中心(主要是纬向运动)的(K，，K，)=(21和8.4x10~6cm2 S-L)，以及在岩心以南(主要是波动运动)的(K，，，)=(4.3和3.5x10~6cm2的S-L)。简单的尺度分析表明，这些与时间相关的运动对地中海盐舌在纬向和经向的传播都起着主导作用。
Lagrangian trajectories from the SOFAR float Mediterranean outflow experiment are used to estimate the low frequency variability and mixing in the vicinity of the Mediterranean salt tongue. Two dominant patterns of Lagrangian variability are observed, (1) nearly zonal low frequency motions and (2) wave-like oscillations with northwest to southeast orientation. The zonal motions are found near the core of the salt tongue in the Canary Basin while the oscillations are generally found to the south and east. It is suggested that the zonal motions are the result of baroclinic instability of the large-scale flow. They have zonally enhanced low frequency variability (periods greater than 200 days) and nearly isotropic mesoscale variability (periods 50 to 200 days). The wave motions are believed to be the signature of radiating baroclinic Rossby waves generated to the south at the Cape Verde Frontal Zone. They are strongly peaked at the mesoscale band and have an essentially isotropic low frequency component. Integral time scales for the zonal motions are relatively long (23 and 13 days for the zonal and meridional directions) while for the wave motions they are short (7.7 and 5.0 days). The resulting eddy diffusivities are found to be non-isotropic and non-homogeneous with (K,, K,) = (21 and 8.4 x lo6 cm2 s-l) in the core of the salt tongue (mainly zonal motions) and (K,, K,,,,) = (4.3 and 3.5 x lo6 cm2 s-l) to the south of the core (mainly wave-like motions). A simple scale analysis indicates that these time dependent motions play the dominant role in the spread of the Mediterranean salt tongue in both the zonal and meridional directions.