Long‐range acoustic transmission in the northwest Atlantic
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An acoustic propagation experiment conducted west of Bermuda during the fall of 1978 demonstrated that individual acoustic arrivals at 900‐km range were stable and identifiable over a 48‐day period. The observed arrival pattern is interpreted by geometric ray theory and by comparison with a ‘synthetic sofargram’ (equivalent to a synthetic seismogram) constructed from WKBJ theory. Using geometric ray theory, we examine the expected generation and annihilation of ray paths as a result of the seasonal erosion of the autumnal thermocline. Many rays are converted from purely refracted to surface reflected/refracted rays. The ultimate goal of this work is to interpret variability in acoustic transmission in terms of ocean variability.Keywords:
Transmission loss
Seismogram
实验直角的功能(文件结束) 分析在这研究被使用为中国海产生历史的温度的主要特徵向量领域(这里指中国海洋的领土) 并且从 1930 ～ 2002 的邻近的水(510 143 侧面) 。好温度侧面被重建基于几在 situ 温度观察和 thermocline 表面下用模型被估计。结果显示出那：1 ) 为学习区域，四个主要部件能向 95% 全面变化解释的前者，和温度的垂直分发是很稳定的使用在里面 situ 温度观察接近表面。 2 )模型确认基于从华东的观察 CTD 数据，海( ECS )，华南海( SCS )和在台湾岛附近的区域证明重建的侧面与信心水平>95%与观察的有高关联，描述 thermocline 的特征到特别很好。在在这三个区域的重建并且观察的侧面之间的平均错误分别地是 0.69 ° C， 0.52 ° C 和 1.18 ° C。它也证明模型 RMS 错误近是不到 or 到 climatological 错误。统计模型能被用来很好估计温度侧面垂直结构。 3 )比较在重建并且观察的侧面，在平均绝对错误是 1.5m ，并且平均相对错误为上面的、更低的 thermocline 边界和坡度是24.7%，8.9%和22.6%的 ECS 表演的结果， 1.4 m 和 0.17 °C /m 之间的 thermocline 特征，分别地。尽管相对错误是明显的，绝对错误是小的。在 SCS，平均绝对错误是 4.1 m， 27.7 m 和 0.007 ° C /m，并且平均相对错误分别地为上面的、更低的 thermocline 边界和坡度是 16.1% ， 16.8% 和 9.5% 。平均相对错误都是 <20% 。尽管更低的 thermocline 边界的平均绝对错误是可观的，但是形成对照到更低的 thermocline 边界(165 m ) 的平均深度的空间规模，平均相对错误是小的(16.8%) 。因此，模型能被用来很好估计 thermocline。
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在赤道的太平洋的表面下的温度异例的偏斜度显示出在东方和西方之间的重要不对称现象。积极温度偏斜度出现在赤道的东方太平洋，当在西方、中央的太平洋的温度偏斜度主要是否定的时。也有温度偏斜度在上面并且在在中央、西方的太平洋的 climatological 平均数 thermocline 下面的不对称现象。积极偏斜度在 thermocline 下面出现，但是偏斜度在 thermocline 上面是否定的。温度偏斜度的特殊垂直不对称现象被说服被归因于对的不对称的温度反应向上并且向下 thermocline 排水量面对观察了上面海洋的垂直热结构。因为积极(否定) 关于深度在下面的温度的第二衍生物(在上面) thermocline，一向上并且一向下与相等的排水量 thermocline 变将在 thermocline 上面导致否定温度偏斜度但是在 thermocline 下面的积极偏斜度。在远东方的赤道的太平洋， thermocline 接近混合的层的底，上面海洋的垂直温度侧面的形状不能被保留。积极偏斜度在远东方的盆在 thermocline 下面并且在 thermocline 上面出现在两个。在中央、东方的太平洋上，表面下的水的异例趋于乘火车进表面混合的层(由在 welling 上面吝啬的 climatological ) 然后影响 SST。因此，积极(否定) 表面下的偏斜度在远东方(中央) 和平可以宠爱积极(否定) SST 偏斜度，它与观察事实一致更多的 La Nina (El Nino ) 发生在中央(东方) 和平。现在的结果在东方太平洋为 El Nino 和 La Nina 振幅不对称现象暗示一个可能的新范例。
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A numerical study on seasonal variations of the thermocline in the South China Sea based on the ROMS
On the basis of the regional ocean modeling system(ROMS), the seasonal variations of the thermocline in the South China Sea(SCS) were numerically investigated. The simulated hydrodynamics are in accordance with previous studies: the circulation pattern in the SCS is cyclonic in winter and anticyclonic in summer, and such a change is mostly driven by the monsoon winds. The errors between the modeled temperature profiles and the observations obtained by cruises are quite small in the upper layers of the ocean, indicating that the ocean status is reasonably simulated. On the basis of the shapes of the vertical temperature profiles, five thermocline types(shallow thermocline, deep thermocline, hybrid thermocline, double thermocline, and multiple thermocline) are defined herein. In winter, when the northeasterly monsoon prevails, most shallow shelf seas in the northwest of the SCS are well mixed, and there is no obvious thermocline. The deep region generally has a deep thermocline, and the hybrid or double thermocline often occurs in the areas near the cold eddy in the south of the SCS. In summer, when the southwesterly monsoon prevails, the shelf sea area with a shallow thermocline greatly expands. The distribution of different thermocline types shows a relationship with ocean bathymetry: from shallow to deep waters, the thermocline types generally change from shallow or hybrid to deep thermocline, and the double or multiple thermocline usually occurs in the steep regions. The seasonal variations of the three major thermocline characteristics(the upper bound depth, thickness, and intensity) are also discussed. Since the SCS is also an area where tropical cyclones frequently occur, the response of thermocline to a typhoon process in a short time scale is also analyzed.
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自从 1950 年代，基于观察温度数据，夏天的长期的可变性黄海冷水里的锋利的 thermocline 质量(YSCWM ) 和华东海寒冷回旋(ECSCE ) 区域被检验。在 thermocline 之间的关系并且大气、海洋强迫用 multiyear 风，自台湾东面的菲律宾海流向日本的暖流分泌物和空气被调查温度数据。结果显示出那：1 ) 在 YSCWM 区域， thermocline 力量关于 4 年、 16 年的时期摆动出现。在夏天和以前的冬季在夏天 thermocline 力量和本地大气的温度之间有高关联；2 ) 在 ECSCE 区域， thermocline 强度与的 interannual 摆动关于一个 4 年的时期(在 El Ni 更强壮 ? o 年) 强烈与本地风应力的被相关。转变从对强壮的 thermocline 弱与 1976/1977 气候移动和自台湾东面的菲律宾海流向日本的暖流体积运输在 1970 年代中期间一致；3 ) 在两个区域的 thermocline 的长期的变化被深层水主要决定，特别在十的 timescale 上。然而，表面水能在 YSCWM 区域在 interannual timescale 上修改 thermocline。
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Abstract The thermocline is a sea layer with a change in temperature to depth quite quickly. We had to study this layer because it had an important contribution to thermohaline flows, upwelling, and fish migration. This paper aimed to map the vertical profiles of temperatures and thermocline gradients in the Andaman waters during the transitional season, October 2017. Analysis of the thermocline layer was based on vertical temperature data from the CMEMS model which were verified with SST from Aqua MODIS 4 km. The thermocline layer was indicated by ΔT / Δz ≥ 0.1 °C and started from the depth of 40 m. CMEMS SST verification on October 2017 showed good results (MAPE = 0.0188, r = 0.68). The thermocline layer was found thicker off the west coast of Sumatra, the Indian Ocean (Station 1) than in the Andaman Sea. Generally, the thermocline layer was at a depth of 66 -131 meters on October 2017. The thermocline gradients were 0.12 - 0.23. These results indicated that in the transitional season, the thermocline location in the Andaman Sea was shallower or less than 200 m.
Mixed layer
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Abstract The Persian Gulf (PG) is a shallow sea connected to the rest of the world by the Strait of Hormuz. Temperature changes in the water column, which indicate the thermocline, are typically explained by the depth of the mixed layer and the thermocline. The thermocline is caused by a sudden decrease in temperature in the water column's subsurface layer, resulting in stratification in the PG from winter to summer. The parameters are approximated numerically through the Princeton Ocean Modeling (POM) method and compared to those determined by some CTD profiles collected in the PG. The most obvious method for approximating thermocline depth is to find the maximum negative slope \(\frac{\partial T}{\partial z}\) in a temperature profile. The method produces applied results with sufficient depth resolution and smooth temperature changes with depth. This method is a component of the Princeton Ocean Modeling (POM) framework for numerically modeling temperature variation in the water basins used in this study. The depth of the mixed layer is approximated by the surface equality temperature (Sea Surface Temperature), regardless of the thermocline approximation. The variable isotherm behavior accurately approximates the thermocline depth. Thermocline formation occurs in the PG during the summer, and this article will conclude using two methods, observational and numerical modeling.
Mixed layer
Stratification (seeds)
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A numerical study on seasonal variations of the thermocline in the South China Sea based on the ROMS
根据为系统(ROMS ) 建模的地区性的海洋，在华南海(SCS ) 的 thermocline 的季节的变化数字地被调查。模仿的水动力学根据以前的研究：在 SCS 的发行量模式在冬季是气旋的并且在夏天，和如此的一个变化逆旋风被季风风主要驾驶。在巡航获得的建模的温度侧面和观察之间的错误在海洋的上面的层是相当小的，显示海洋地位相当被模仿。根据垂直温度侧面的形状，五种 thermocline 类型(浅 thermocline，深 thermocline，混合 thermocline，两倍 thermocline，和多重 thermocline ) 此处被定义。在冬季，什么时候在东北，季风占优势，在 SCS 的西北的很浅的架海很好被混合，并且没有明显的 thermocline。深区域通常有深 thermocline，并且混合或双的 thermocline 经常在 SCS 的南方在冷旋涡附近发生在区域。在夏天，当西南的季风占优势时，有浅 thermocline 的架海区域极大地膨胀。不同 thermocline 类型的分发与海洋深测术显示出一种关系：从对深水浅， thermocline 类型通常变化从对浅或混合深， thermocline，和双或多重的 thermocline 通常发生在陡峭的区域。三个主要 thermocline 特征(上面的界限深度，厚度，和紧张) 的季节的变化也被讨论。因为 SCS 也是热带气旋经常发生的一个区域，到在短时间规模的一个台风过程的 thermocline 的反应也被分析。
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Based on the data of temperature,salinity and DO observed in the Changjiang Estuary covering 54 stations in late summer,2009,vertical structure types of water temperature were classified by the method of vertical gradient,and the parameters including depth and intensity of thermocline and vertical gradient of DO on the water layer of thermocline were calculated. In late summer,the distribution of temperature vertical structure and intensity of thermocline off the Changjiang Estuary was a situation of confluence and mixing by the dilute water of Changjiang,the coastal current of Yellow Sea,the warm upper water of Taiwan Warm Current and the cold deep water of Taiwan Warm Current. Correlation analysis showed that,there was a negative correlation between the depth of thermocline and the vertical gradient of DO on the layer of thermocline,there was a positive correlation between the thermocline depth and the vertical minimum DO,and also a positive correlation between the thermocline intensity and vertical gradient of DO on the layer of thermocline. The thermocline intensity,especially the intensity of upper thermocline which was near sea surface,the origin of DO,has a strong correlation( r = 0. 69) with the DO vertical gradient on the layer of thermocline. The shallower and the stronger of the thermocline,the greater effect of the thermocline on the hypoxia of deep water. Thermocline,in particular,the upper thermocline hindered the surface water with saturated DO mixed with the deep water,played a role of physical barrier of oxygen vertical transportation.The thermocline was an important environmental control factor of the hypoxia off the Changjiang Estuary from late spring to autumn,covering a period of occurrence,development,maintenance and decay of the hypoxia.
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