Quantitative evaluation of turbulent mixing in the Central Equatorial Pacific
Quantitative evaluation of turbulent mixing in the Central Equatorial Pacific
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DOI：
10.1007/s10872-013-0213-5
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发表时间：
2012-12
影响因子：
2.3
通讯作者：
Lingqiao Cheng;Y. Kitade
中科院分区：
文献类型：
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作者：
Lingqiao Cheng;Y. Kitade
通过对赤道中部太平洋经向和垂直大区域微结构测量和电导率温度廓线(CTD)观测资料的分析，定量地评价了赤道中部太平洋的湍流混合。结果表明，在赤道1°范围内，从海面混合层到赤道1°以下的低理查森数区，具有耗散率的强湍流混合ε(>；O(10−7)/W/kg−1)表明，湍流混合与切变不稳定有密切关系，ε>；O(10−7)/W/kg−1和湍流扩散系数Kρ>；O(10−3)/m2s−1在近地表到85 db的台站，甚至向南超过3°S，已经远离赤道潜流的南界(~2°S)。计算了湍流引起的热通量和盐度通量，两者的最大值都出现在赤道上升区，前者是向下的，而后者是向上的。因此，上升流区的垂直速度估计与其他方法得出的结果相似。这些通量和垂直速度表明，湍流混合对于维持上层的良好混合至关重要。其次，在中间区域(>；500db)，用Thorpe方法对CTD资料进行了湍流涡旋的研究。发现了大量的倾覆，空间平均Kρ(700-1000db)为3.3亿×10−6m2s−1，相应的Kρ-max也达到(10−4)m2s−1在北部(3°-13°N)。结果表明，在中间区域，发生了相当大的湍流混合，并缓和了水团的性质。
Turbulent mixing in the central equatorial Pacific has been quantitatively evaluated by analyzing data from microstructure measurements and conductivity temperature depth profiler (CTD) observations in a meridionally and vertically large region. The result that strong turbulent mixing with dissipation rateε(>O(10−7) W kg−1), continuing from sea-surface mixed layer to low Richardson number region below, in the area within 1° of the equator, shows that turbulent mixing has a close relationship to shear instability.ε>O(10−7) W kg−1and turbulent diffusivityKρ>O(10−3) m2s−1were obtained from near-surface to 85 db at stations even southwardly beyond 3°S, where it is already far from the southern boundary (~2°S) of the Equatorial Undercurrent. Turbulence-induced heat flux and salinity flux were calculated, and both had their maxima in the equatorial upwelling region, though the former was downward and the latter was upward. Accordingly, vertical velocity in the upwelling region was estimated to be similar to the results derived by other methods. These fluxes and the vertical velocity suggest the critical importance of turbulent mixing in maintaining the well-mixed upper layer. Secondly, in the intermediate region (>500 db), turbulent eddies were investigated by applying Thorpe’s method to the CTD data. A large number of overturns were detected, with spatial-averagedKρ(700–1,000 db) being 3.3 × 10−6m2s−1, and the correspondingKρ-maxreaching toO(10−4) m2s−1in the north (3°–13°N). The results suggest that, in the intermediate region, considerable turbulent mixing occurs and moderates the properties of the water masses.