Comparison of Turbulence Intensity from CTD-Attached and Free-Fall Microstructure Profilers
Comparison of Turbulence Intensity from CTD-Attached and Free-Fall Microstructure Profilers
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DOI：
10.1175/jtech-d-17-0069.1
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发表时间：
2018-01-01
影响因子：
2.2
通讯作者：
Nagasawa, Maki
中科院分区：
文献类型：
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作者：
Goto, Yasutaka;Yasuda, Ichiro;Nagasawa, Maki
湍流强度估计从快速响应热敏电阻之间的电导率-温度-深度（CTD）的连接和自由落体的微观结构剖析，在2小时内在同一位置进行比较。一致性通常良好，但在CTD附加方法中偶尔出现偏离对数正态分布的过度高估值。这些被高估的异常值在原始温度梯度曲线中作为尖峰斑块是明显的。当CTD帧的下降速率W（ms（-1））小且其标准偏差W-sd大时，它们经常发生。这些高估的离群值可以通过拒绝W-sd > 0.2 W - 0.06的标准的数据来有效地去除，其中W和W-sd是针对1 s间隔计算的。经过数据筛选后，对于50米深度平均数据，CTD附着式剖面仪和自由落体式剖面仪的热量和能量耗散chi和X2在10（10）< chi < 10（-7）℃-2 s（-1）和10（-10）<X2 < 10（-8）W kg（-1）的范围内分别保持在3倍以内。在湍流度大于10（-8）的较高湍流度范围内，CTD附加方法的能量耗散往往被低估。这可能是由于热敏电阻响应对于CTD帧的较快下降速率（类似于1 ms（-1））的校正不足。由于在中深海的大部分区域湍流小于10（-8），使用CTD附加的快速响应湍流仪提供了一种有效的方法来扩展目前稀疏的湍流观测。
Turbulence intensity estimated from fast-response thermistors is compared between conductivity-temperature-depth (CTD)-attached and free-fall microstructure profilers, conducted at the same location within 2 h. The agreement is generally good but anomalously overestimated values, deviating from a lognormal distribution, appear sporadically in the CTD-attached method. These overestimated outliers are evident as spiky patches in the raw temperature gradient profiles. They often occur when the fall rate of the CTD frame W (m s(-1)) is small and its standard deviation W-sd is large. These overestimated outliers can be efficiently removed by rejecting data with the criteria of W-sd > 0.2 W - 0.06, where W and W-sd are computed for a 1-s interval. After the data screening, thermal and energy dissipation, chi and epsilon, from CTD-attached and free-fall profilers are consistent within a factor of 3 in the ranges of 10 (10)< chi < 10(-7)degrees C-2 s(-1) and 10(-10) < epsilon < 10(-8) W kg(-1), respectively, for 50-m depth-averaged data. Energy dissipation from the CTD-attached method tended to be underestimated in the higher turbulence range of epsilon > 10(-8). This could be due to insufficient correction of the thermistor response for the faster fall rate (similar to 1 ms(-1)) of CTD frames. Since epsilon < 10(-8) in most parts of the intermediate and deep ocean, use of the CTD-attached fast-response thermistors provides an efficient way to expand the presently sparse turbulence observations.