MIXING IN THE EQUATORIAL SURFACE-LAYER AND THERMOCLINE
MIXING IN THE EQUATORIAL SURFACE-LAYER AND THERMOCLINE
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DOI：
10.1029/jc094ic02p02005
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发表时间：
1989-02-15
影响因子：
3.6
通讯作者：
PAULSON, CA
中科院分区：
文献类型：
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作者：
MOUM, JN;CALDWELL, DR;PAULSON, CA
1984年11月，在赤道（140°W）进行了12天的微结构测量，结果显示太阳加热和风的日循环对上层海洋混合的影响惊人地强烈。由于实验期间大气强迫和海流的变化有限，每日混合循环中的过程每天都是相似的。只有混合的强度不同。昼夜表层的下边界分离两个不同的混合制度，昼夜表层和温跃层。在昼夜表面层（延伸到10 - 35 m深度）内，湍流动能耗散率ε变化相对较小。虽然表层深度的变化与海-气表面浮力产生湍流动能（或简单地说，表面浮力通量）的方向的每日变化相一致，但ε相对于浮力通量的变化明显大于简单对流层的预期。在昼夜表面层以下的温跃层中，ε是高度间歇性的;昼夜循环更强，并且可变性被持续2-3小时的湍流“爆发”增强，这可能与内波破碎事件有关。穿过20 m深度的湍流热通量几乎等于表面热通量减去穿透20 m以下的辐照度。70%的地表热通量通过湍流混合垂直输送到30 m以下的水体。只有极少量的渗透到赤道暗流的核心。梯度Richardson数Ri区分统计上不同的混合环境。然而，ε不能从Ri的值预测，因为混合的强度取决于强迫的强度，而不是由Ri单独指定的。
Twelve days of microstructure measurements at the equator (140°W) in November 1984 showed a surprisingly strong effect of both the daily cycle of solar heating and wind on mixing in the upper ocean. Because of limited variations in atmospheric forcing and currents during the experiment, processes in the daily mixing cycle were similar from day to day. Only the intensity of mixing varied. The lower boundary of the diurnal surface layer separated two distinct mixing regimes, the diurnal surface layer and the thermocline. Within the diurnal surface layer (which extended to 10‐ to 35‐m depth), turbulent kinetic energy dissipation rates ε varied relatively little. Although variations in surface layer depth coincided with the daily change in direction of air‐sea surface buoyancy production of turbulent kinetic energy (or simply, the surface buoyancy flux), ε was significantly greater relative to the buoyancy flux than was expected for a simple convective layer. In the thermocline below the diurnal surface layer, ε was highly intermittent; the day‐night cycle was stronger, and variability was enhanced by turbulent “bursts” of 2–3 hours duration, which may be related to internal wave breaking events. The turbulent heat flux crossing 20‐m depth was almost equal to the surface heat flux less the irradiance penetrating below 20 m. Seventy percent of the surface heat flux was transported vertically to the water below 30 m by turbulent mixing. Only a negligible amount penetrated to the core of the Equatorial Undercurrent. The gradient Richardson numberRidistinguishes between statistically different mixing environments. However, ε cannot be predicted from the value ofRi, since the intensity of mixing depends on the intensity of forcing in a way not specified by the value ofRialone.