Measurement of Vertical Kinetic Energy and Vertical Velocity Skewness in Oceanic Boundary Layers by Imperfectly Lagrangian Floats
Measurement of Vertical Kinetic Energy and Vertical Velocity Skewness in Oceanic Boundary Layers by Imperfectly Lagrangian Floats
复制标题
不完全拉格朗日浮子测量海洋边界层垂直动能和垂直速度偏度
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
E. D’Asaro
中科院分区：
文献类型：
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作者：
R. Harcourt;E. D’Asaro
摘要利用大涡模拟（LES）模式中的模拟浮标和两个浮标数据集，研究了上升浮力对拉格朗日浮标测量风驱动的上层海洋边界层中垂直流体速度w的欧拉平均方差和偏度的影响。接近中性浮力的漂浮物被湍流速度反复平流穿过边界层。它们的垂直位置Z由压力测量值确定;它们的W方差<$WW <$F和偏度SWE由浮动W = dZ/dt的时间序列确定。如果浮子的浮力很小，那么模拟的浮子可以准确地测量欧拉速度;也就是说，δW2 =<$WW <$F − <$WW <$E和δSW =<$− SwE分别比<$WW <$E和SwE小。如果浮体是有浮力的，因此相对于水具有向上的垂直速度Wbias，则δW2和δSW可以变得显著。浮力导致浮标在浅深度和强垂直方向上过采样。
Abstract The effects of upward buoyancy on the accuracy with which Lagrangian floats can measure the Eulerian mean variance 〈ww〉E and skewness SwE of vertical fluid velocity w in the wind-driven upper-ocean boundary layer is investigated using both simulated floats in large-eddy simulation (LES) models and two float datasets. Nearly neutrally buoyant floats are repeatedly advected by the turbulent velocities across the boundary layer. Their vertical position Z is determined from pressure measurements; their W variance 〈WW〉F and skewness SWE are determined from the time series of float W = dZ/dt. If the float buoyancy is small, then the simulated floats measure the Eulerian velocity accurately; that is, δW2 = 〈WW〉F − 〈ww〉E and δSW = SWF − SwE are small compared to 〈ww〉E and SwE respectively. If the floats are buoyant, and thus have an upward vertical velocity Wbias relative to the water, then δW2 and δSW can become significant. Buoyancy causes the floats to oversample both shallow depths and strong vertica...