Mixed and mixing layer depths in the ocean surface boundary layer under conditions of diurnal stratification
Mixed and mixing layer depths in the ocean surface boundary layer under conditions of diurnal stratification
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DOI：
10.1002/2014gl061939
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发表时间：
2014-12
影响因子：
5.2
通讯作者：
G. Sutherland;G. Reverdin;L. Marié;B. Ward
中科院分区：
文献类型：
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作者：
G. Sutherland;G. Reverdin;L. Marié;B. Ward
从副热带大西洋表层盐度实验(Strasse)巡航中得到了混合层(MLD)和混合层(XLD)深度的比较。这项研究包括在相当平静和中等条件(2<；U10<；10m S−1)和强太阳加热O(1000W m−2)条件下的400个微结构剖面。XLD是根据湍流耗散率降低到假设的背景水平来确定的。测试了本底耗散水平的两种不同阈值，10−8和10−9 m2 S−3，并与使用密度阈值计算的最大似然比进行了比较。在对流过程中，较大的背景阈值与MLD一致，但在夜间对流过程中仅扩展到MLD的一半；而在对流过程中，较小的背景阈值与MLD吻合得很好，但在再层化过程中，背景阈值的深度增加了2倍。观察表明，在浮力驱动的情况下，可以使用更大的密度阈值来确定MLD。
A comparison between mixed (MLD) and mixing (XLD) layer depths is presented from the SubTRopical Atlantic Surface Salinity Experiment (STRASSE) cruise in the subtropical Atlantic. This study consists of 400 microstructure profiles during fairly calm and moderate conditions (2 < U10 < 10 m s−1) and strong solar heating O(1000 W m−2). The XLD is determined from a decrease in the turbulent dissipation rate to an assumed background level. Two different thresholds for the background dissipation level are tested, 10−8 and 10−9 m2 s−3, and these are compared with the MLD as calculated using a density threshold. The larger background threshold agrees with the MLD during restratification but only extends to half the MLD during nighttime convection, while the lesser threshold agrees well during convection but is deeper by a factor of 2 during restratification. Observations suggest the use of a larger density threshold to determine the MLD in a buoyancy driven regime.