Turbulent transport from an arctic lead: A large-eddy simulation
Turbulent transport from an arctic lead: A large-eddy simulation
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来自北极的湍流传输：大涡模拟
DOI：
10.1007/bf02215457
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发表时间：
1992
影响因子：
4.3
通讯作者：
S. Burk
中科院分区：
文献类型：
--
作者：
J. W. Glendening;S. Burk
北极“铅”是指北极冰层上的裂口，使寒冷的大气层与相对温暖的海洋接触。我们采用大涡模式，显式地计算了大气对200米宽铅的三维湍流响应。地面热通量产生了单个准随机涡旋的湍流“羽流”，而不是连续的上升气流，它穿透到稳定的大气中，向上输送热量。最大上升气流速度和湍流发生在铅的下风方向，而不是在铅本身上方，因为单个热涡的发展时间长于它穿过铅的时间。受影响的垂直区虽然在铅本身上方较浅，但在铅的下风向600米处增长到65米的高度；超过这一高度，湍流区的深度随着涡旋的减弱而减小。垂直湍流热通量的最大值出现在铅的下风向边缘，超过这一点的相对最大值向上延伸到羽流中。铅的下风立即产生负的表面热通量，形成一个不断增长的稳定层，但在该内边界层上方，湍流热通量仍为正值。上升气流的最大值通常为28厘米/S，但补偿下沉气流会导致羽流中的时间平均垂直速度小于1厘米/S。有条件抽样将上升气流和下降气流的贡献分开。给出了水平涡旋发展距离和垂直羽流穿透高度的计算公式。比较了平均输送和湍流输送对垂直换热和水平换热的相对重要性：湍流在垂直换热中起主导作用，而平均平流在水平输送中起主导作用，这些相互抵消的输送产生一种准定态。
The upward transfer of heat from ocean to atmosphere is examined for an Arctic “lead”, a break in the Arctic ice which allows contact between the cold atmosphere and the relatively warm ocean. We employ a large-eddy model to compute explicitly the three-dimensional turbulent response of the atmosphere to a lead of 200 m width. The surface heat flux creates a turbulent “plume” of individual quasi-random eddies, not a continuous updraft, which penetrate into the stable atmosphere and transport heat upward.Maximum updraft velocities and turbulence occur downwind of the lead rather than over the lead itself, because the development time of an individual thermal eddy is longer than its transit time across the lead. The affected vertical region, while shallow over the lead itself, grows to a height of 65m at 600 m downwind of the lead; beyond that, the depth of the turbulent region decreases as the eddies weaken. The maximum vertical turbulent heat flux occurs at the downwind edge of the lead, beyond which a relative maximum extends upward into the plume. Negative surface heat flux immediately downwind of the lead creates a growing stable layer, but above that internal boundary layer the turbulent heat flux is still positive. Updraft maxima are typically 28 cm/s, but compensating downdrafts result in time-averaged vertical velocities of less than 1 cm/s in the plume. Conditional sampling separates the updraft and downdraft contributions. Formulas for the horizontal eddy development distance and for the vertical plume penetration height are presented. The relative importance of mean and turbulent transport is compared for both vertical and horizontal heat transfer: turbulence dominates the vertical heat transport whereas mean advection dominates the horizontal transport, these offsetting transports producing a quasi-stationary state.