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1.
Mesoscale eddies, which are mainly caused by baroclinic effects in the ocean, are common oceanic phenomena in the Northwest Pacific Ocean and play very important roles in ocean circulation, ocean dynamics and material energy transport. The temperature structure of mesoscale eddies will lead to variations in oceanic baroclinity, which can be reflected in the sea level anomaly (SLA). Deep learning can automatically extract different features of data at multiple levels without human intervention, and find the hidden relations of data. Therefore, combining satellite SLA data with deep learning is a good way to invert the temperature structure inside eddies. This paper proposes a deep learning algorithm, eddy convolution neural network (ECN), which can train the relationship between mesoscale eddy temperature anomalies and sea level anomalies (SLAs), relying on the powerful feature extraction and learning abilities of convolutional neural networks. After obtaining the temperature structure model through ECN, according to climatic temperature data, the temperature structure of mesoscale eddies in the Northwest Pacific is retrieved with a spatial resolution of 0.25° at depths of 0–1 000 m. The overall accuracy of the ECN temperature structure is verified using Argo profiles at the locations of cyclonic and anticyclonic eddies during 2015–2016. Taking 10% error as the acceptable threshold of accuracy, 89.64% and 87.25% of the cyclonic and anticyclonic eddy temperature structures obtained by ECN met the threshold, respectively. 相似文献
2.
两个西边界流延伸体区域中尺度涡统计特征分析 总被引：3，自引：2，他引：1
黑潮和湾流是世界大洋中最典型的两支西边界流，黑潮延伸体（Kuroshio Extention，KE）和湾流延伸体（Gulf Stream Extention，GSE）区域中尺度涡活动十分活跃。本文综合利用卫星高度计资料和Argo浮标资料，对KE和GSE区域中尺度涡的表层特征及其对温盐影响进行了统计研究和对比分析。结果表明:黑潮和湾流主轴附近为涡旋频率的高值区，主轴南北两侧分别以气旋涡和反气旋涡数量占多，主轴附近的涡旋强度明显大于其他区域；两个区域的涡旋以西向移动为主，气旋涡和反气旋涡都具有向南（赤道）偏离的趋势；两个区域的涡旋数量都以夏、秋季较多，涡旋强度都在春、夏季较大，且GSE区域涡旋强度明显大于KE区域；气旋涡（反气旋涡）引起内部明显的温度负（正）异常，KE区域气旋涡（反气旋涡）内部呈"负-正"（"正-负"）上下层相反的盐度异常分布，GSE区域气旋涡（反气旋涡）在各层呈现较为一致的盐度负（正）异常；两个区域中尺度涡对温盐场的平均影响深度可达1 000×104 Pa以上。 相似文献
3.
基于南海东北部1998~2019年的多源卫星遥感数据和风场再分析数据, 较系统地分析了南海东北部涡旋内部叶绿素a浓度的分布特征, 通过量化统计和涡心坐标系参数合成等方法探究了中尺度涡对叶绿素a浓度变化的影响规律及潜在机制。结果表明: (1)南海东北部约有60%的中尺度涡旋内部存在叶绿素a浓度增加和减少的现象。(2)南海东北部中尺度涡内部叶绿素a扰动受到涡旋抽吸和涡致Ekman抽吸机制的共同调控, 其中约有38% (39%)的暖(冷)涡内涡旋抽吸的贡献更大, 21% (24%)的暖(冷)涡内涡致Ekman抽吸的贡献更大。(3)南海东北部中尺度涡生命周期内的海表叶绿素a浓度变化存在显著的阶段性差异, 在冷暖涡的生成期, 涡旋抽吸的作用更为显著, 而在冷暖涡的顶峰和消亡期, 涡致Ekman抽吸的作用更为明显。上述研究结果有助于理解南海东北部初级生产力对中尺度涡的响应过程与机理, 对认识海洋物理-生物耦合过程具有一定的参考价值和研究意义。 相似文献
4.
Repeated hydrographic casts, mooring time series and satellite sea surface temperature collected during the CANALES experiment (1996–98) are used to describe the thermohaline circulation in the Balearic Channels (western Mediterranean) and to analyze its variability. Mass transports are estimated by inverse calculations. The role played by each channel in the meridional water exchange is clarified: the Ibiza Channel funnels southward cool, saline, northern waters whereas the Mallorca Channel appears as the preferred route for the northward progression of warm, fresh, southern waters. A neat interannual trend is revealed by the continuous decrease of the amount of Western Mediterranean Intermediate Waters (WIW) brought by the Northern Current, reflecting the increase in temperature of the winter mixed layer in the northern Mediterranean that occurred each year between 1996 and 1998. A clear seasonal signal was also seen in the transport of the Northern Current which decreased from 1 to 1.4 Sv in winter to < 0.5 Sv in summer. The current intensified again in fall. A number of mesoscale eddies, from 20 to 70 km in size, most of them anticyclonic vortex eddies were brought by the unstable Northern Current, these eddies strongly perturbed the water exchange in the Ibiza Channel forcing retroflections of northern waters back to the north-east into the Balearic Current. These eddies either stayed stalled for several months in the Gulf of Valencia to the north of the channel, or were slowly funnelled southward through the channel narrows. A decreasing trend was observed in the mesoscale activity of the Northern Current between 1996 and 1998. Conversely, large, anticyclonic eddies, 150-km diameter, progressively invaded the Algerian Basin to the south of the channels in 1997–98 and forcing northward inflows (up to 0.75 Sv) of fresh and warm waters of Atlantic origin (AW) into the Mallorca Channel. The marked interannual differences observed in both northern and southern eddy activity may be linked to the interannual variability of the large scale thermohaline circulation. 相似文献
5.
南印度洋中尺度涡统计特征及三维合成结构研究 总被引：2，自引：2，他引：0
南印度洋是海洋中尺度涡的多发区域。本文利用卫星高度计资料及Argo浮标资料,对南印度洋（10°~35°S, 50°~120°E）区域中尺度涡的分布、表观特征等进行了统计分析,采用合成方法,构建了该区域中尺度涡的三维温盐结构。结果表明,涡旋频率呈明显的纬向带状分布,在18°~30°S存在一个明显的涡旋频率带状高值区;涡旋半径具有由南至北逐渐增大的趋势;长周期涡旋在其生命周期内,半径、涡动能、涡能量密度、涡度等性质均经历了先增大而后减小的过程;涡旋以西向运动为主,在经向上移动距离较小,长周期气旋（反气旋）涡具有明显的偏向极地（赤道）移动的倾向;涡旋平均移动速度为5.9 cm/s,速度大小大致沿纬向呈带状分布。在混合层以下,气旋涡（反气旋涡）内部分别呈现明显的温度负（正）异常,且分别存在两个位温负（正）异常的冷（暖）核结构;气旋涡（反气旋涡）整体上呈现"正-负"（"负-正"）上下层相反的盐度异常结构。中尺度涡对温盐的平均影响深度可达1 000×104 Pa以上。 相似文献
6.
Baiyang Chen Lingling Xie Quanan Zheng Lei Zhou Lei Wang Baoxin Feng Zipeng Yu 《海洋学报(英文版)》2020,39(12):11-20
Using the mesoscale eddy trajectory atlas product derived from satellite altimeter data from 1993 to 2016, this study analyzes statistical characteristics and seasonal variability of mesoscale eddies in the Banda Sea of the Indonesian seas. The results show that there were 147 mesoscale eddies that occurred in the Banda Sea, of which 137 eddies were locally generated and 10 originated from outside. The total numbers of cyclonic eddies (CEs, clockwise) and anticyclonic eddies (AEs, anticlockwise) are 76 and 71, respectively. Seasonally, the number of CEs (AEs) is twice larger than the number of AEs (CEs) in winter (summer). In winter, CEs are distributed in the southern and AEs in the northern basins, respectively, but the opposite thing occurs in summer, i.e., the polarities of mesoscale eddies observed at the same location reverse seasonally. The mechanisms of polarity distribution reversal (PDR) of mesoscale eddies are examined with reanalysis data of ocean currents and winds. The results indicate that the basin-scale vorticity, wind stress curl, and the meridional shear of zonal current reverse seasonally, which are favorable to the PDR of mesoscale eddies. The possible generation mechanisms of mesoscale eddies include direct wind forcing, barotropic and baroclinic instabilities, of which the direct wind forcing should play the dominant role. 相似文献
7.
《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(17):1351-1362
We use a 9-km pan-Arctic ice–ocean model to better understand the circulation and exchanges in the Bering Sea, particularly near the shelf break. This region has, historically, been undersampled for physical, chemical, and biological properties. Very little is known about how water from the deep basin reaches the large, shallow Bering Sea shelf. To address this, we examine here the relationship between the Bering Slope Current and exchange across the shelf break and resulting mass and property fluxes onto the shelf. This understanding is critical to gain insight into the effects that the Bering Sea has on the Arctic Ocean, especially in regard to recent indications of a warming climate in this region. The Bering Sea shelf break region is characterized by the northwestward-flowing Bering Slope Current. Previously, it was thought that once this current neared the Siberian coast, a portion of it made a sharp turn northward and encircled the Gulf of Anadyr in an anticyclonic fashion. Our model results indicate a significantly different circulation scheme whereby water from the deep basin is periodically moved northward onto the shelf by mesoscale processes along the shelf break. Canyons along the shelf break appear to be more prone to eddy activity and, therefore, are associated with higher rates of on-shelf transport. The horizontal resolution configured in this model now allows for the representation of eddies with diameters greater than 36 km; however, we are unable to resolve the smaller eddies. 相似文献
8.
Wenjin Sun Yu Liu Gengxin Chen Wei Tan Xiayan Lin Yuping Guan Changming Dong 《海洋学报(英文版)》2021,40(10):17-29
In general, a mesoscale cyclonic (anticyclonic) eddy has a colder (warmer) core, and it is considered as a cold (warm) eddy. However, recently research found that there are a number of “abnormal” mesoscale cyclonic (anticyclonic) eddies associated with warm (cold) cores in the South China Sea (SCS). These “abnormal” eddies pose a challenge to previous works on eddy detection, characteristic analysis, eddy-induced heat and salt transports, and even on mesoscale eddy dynamics. Based on a 9-year (2000–2008) numerical modelling data, the cyclonic warm-core eddies (CWEs) and anticyclonic cold-core eddies (ACEs) in the SCS are analyzed. This study found that the highest incidence area of the “abnormal” eddies is the northwest of Luzon Strait. In terms of the eddy snapshot counting method, 8 620 CWEs and 9 879 ACEs are detected, accounting for 14.6% and 15.8% of the total eddy number, respectively. The size of the “abnormal” eddies is usually smaller than that of the “normal” eddies, with the radius only around 50 km. In the generation time aspect, they usually appear within the 0.1–0.3 interval in the normalized eddy lifespan. The survival time of CWEs (ACEs) occupies 16.3% (17.1%) of the total eddy lifespan. Based on two case studies, the intrusion of Kuroshio warm water is considered as a key mechanism for the generation of these “abnormal” eddies near the northeastern SCS. 相似文献
9.
建立了一个描述中尺度涡的新的非线性方程,然后利用变分原理研究了孤立涡旋的Liapunov稳定性,指出反气旋和气旋涡都是稳定的。数值计算结果发现在β效应的作用下这些涡旋都向西移动而不存在向南的移动,然而在反气旋涡的上游存在一个孤立地形(例如海山)的话,孤立地形会使反气旋涡向南移动,而且移动的轨迹取决于孤立地形的位置。当两个反气旋涡同时存在并发生相互作用时,上游孤立地形使这两个反气旋涡产生弱合并并出现弱分离。而且孤立地形的位置对这两个涡的移动和旋转有重要影响。 相似文献
10.
11.
黑潮延伸体邻近区域中尺度涡特征统计分析 总被引：7，自引：3，他引：4
本文利用20年的卫星高度计资料,对黑潮延伸体邻近海区(25°—45°N,135°E—175°W)中尺度涡的统计特征以及季节变化进行了统计研究。基于涡旋自动识别方法,共识别出本区域3006个气旋涡轨迹和2887个反气旋涡轨迹,其平均周期分别为9.99周和11.00周,平均半径分别为69.5km和71.8km。长生命周期涡旋的平均半径、涡度、涡动能(EKE)和涡旋能量密度(EI)在生命周期内大致都经历了增大-基本保持不变-减小这三个阶段。绝大多数涡旋沿纬线向西移动,经向移动距离较小,气旋涡和反气旋涡在西向传播过程中都具有明显的向南(赤道)偏离趋势。涡旋的生成数量与总数量均在春夏季达到最多,且这一时期涡旋的平均涡度、EKE、EI处于较高水平。 相似文献
12.
The HNLC waters of the Gulf of Alaska normally receive too little iron for primary productivity to draw down silicate and nitrate in surface waters, even in spring and summer. Our observations of chlorophyll sensed by SeaWiFS north of 54°N in pelagic waters (>500 m depth) of the gulf found that, on average, more than half of all surface chlorophyll was inside the 4 cm contours of anticyclonic mesoscale eddies (the ratio approaches 80% in spring months), yet these contours enclosed only 10% of the total surface area of pelagic waters in the gulf. Therefore, eddies dominate the chlorophyll and phytoplankton distribution in surface pelagic waters. We outline several eddy processes that enhance primary productivity. Eddies near the continental margin entrain nutrient - (and Fe) - rich and chlorophyll-rich coastal waters into their outer rings, advecting these waters into the basin interior to directly increase phytoplankton populations there. In addition, eddies carry excess nutrients and iron in their core waters into pelagic regions as they propagate away from the continental margin. As these anticyclonic eddies decay, their depressed isopycnals relax upward, injecting nutrients up toward the surface layer. We propose that this transport brings iron and macro-nutrients toward the surface mixed layer, where they are available for wind-forced mixing to bring them to surface. These mesoscale eddies decay slowly, but steadily, perhaps providing a relatively regular upward supply of macro-nutrients and iron toward euphotic layers. They might behave as isolated oases of enhanced marine productivity in an otherwise iron-poor basin. We note that much of this productivity might be near or just below the base of the surface mixed layer, and therefore poorly sampled by colour-sensing satellites. It is possible, then, that eddies enrich phytoplankton populations to a greater extent than noted from satellite surface observations only. 相似文献
13.
Numerical study on the interactions between a mesoscale eddy and a western boundary current 总被引：4，自引：3，他引：1
A reduced-gravity primitive equation eddy resolving model has been used to study the decay of a mesoscale eddy as it migrates
toward a western boundary current (WBC) region. The model results indicated that the gradient of the relative vorticity to
the east of the WBC is an important factor in the interaction between an eddy and a WBC. A circular eddy is deformed into
an elliptical form during the eddy–WBC interaction with the major axis of a cyclonic/anticyclonic eddy aligning in the NW/NNE
direction, respectively. Because of the difference in the major axes orientations for the cyclonic and anticyclonic eddies,
the kinetic energy transfer between a WBC and a particular eddy has very different behavior. A cyclonic eddy loses its energy
to the mean field, whereas an anticyclonic eddy can obtain energy from the mean flow during the WBC–eddy interaction. An anticyclonic
eddy, however, still decayed from losing its water and friction dissipation during the interaction period. 相似文献
14.
15.
Various kinds of datasets, such as satellite-derived sea surface temperature (SST), sea surface height, surface velocity produced
by combining surface drifter and satellite altimeter data, and hydrographic data, led to the discovery of an anticyclonic
eddy with lower SST than those of surrounding waters in the Kuroshio recirculation region south of Shikoku, as if the eddy
were cyclonic. This anticyclonic eddy was formed east of Kyushu in late August to early September 1999 from the merger of
two anticyclonic eddies which had migrated in the recirculation region to the sea south of Japan from the east. After the
merger, the anticyclonic eddy strengthened abruptly and began to exhibit the low SST. In October, this eddy coalesced with
the Kuroshio and moved swiftly eastward, accompanied by an amplitude growth of the Kuroshio meander. In mid November, off
the Kii Peninsula, the eddy detached from the meandering Kuroshio. It then moved southwestward and again slowly propagated
westward along the 30°N line. During this period, at least from late October 1999 to January 2000, SSTs over the anticyclonic
eddy were found to be continuously lower than those of surrounding waters. This case tells us that we have to pay careful
attention to the interpretation of mesoscale SST distributions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Global observations of nonlinear mesoscale eddies 总被引：51，自引：0，他引：51
Sixteen years of sea-surface height (SSH) fields constructed by merging the measurements from two simultaneously operating altimeters are analyzed to investigate mesoscale variability in the global ocean. The prevalence of coherent mesoscale features (referred to here as “eddies”) with radius scales of O(100 km) is readily apparent in these high-resolution SSH fields. An automated procedure for identifying and tracking mesoscale features based on their SSH signatures yields 35,891 eddies with lifetimes ?16 weeks. These long-lived eddies, comprising approximately 1.15 million individual eddy observations, have an average lifetime of 32 weeks and an average propagation distance of 550 km. Their mean amplitude and a speed-based radius scale as defined by the automated procedure are 8 cm and 90 km, respectively.The tracked eddies are found to originate nearly everywhere in the World Ocean, consistent with previous conclusions that virtually all of the World Ocean is baroclinically unstable. Overall, there is a slight preference for cyclonic eddies. However, there is a preference for the eddies with long lifetimes and large propagation distances to be anticyclonic. In the southern hemisphere, the distributions of the amplitudes and rotational speeds of eddies are more skewed toward large values for cyclonic eddies than for anticyclonic eddies. As a result, eddies with amplitudes >10 cm and rotational speeds >20 cm s−1 are preferentially cyclonic in the southern hemisphere. By contrast, there is a slight preference for anticyclonic eddies for nearly all amplitudes and rotational speeds in the northern hemisphere.On average, there is no evidence of anisotropy of these eddies. Their average shape is well represented as Gaussian within the central 2/3 of the eddy, but the implied radius of maximum rotational speed is 64% smaller than the observed radius of maximum speed. In part because of this mismatch between the radii of maximum axial speed in the observations and the Gaussian approximation, a case is made that a quadratic function that is a very close approximation of the mode profile of the eddy (i.e., the most frequently occurring value at each radius) is a better representation of the composite shape of the eddies. This would imply that the relative vorticity is nearly constant within the interiors of most eddies, i.e., the fluid motion consists approximately of solid-body rotation.Perhaps the most significant conclusion of this study is that essentially all of the observed mesoscale features outside of the tropical band 20°S-20°N are nonlinear by the metric U/c, where U is the maximum circum-average geostrophic speed within the eddy interior and c is the translation speed of the eddy. A value of U/c > 1 implies that there is trapped fluid within the eddy interior. Many of the extratropical eddies are highly nonlinear, with 48% having U/c > 5 and 21% having U/c > 10. Even in the tropics, approximately 90% of the observed mesoscale features are nonlinear by this measure.Two other nondimensional parameters also indicate strong degrees of nonlinearity in the tracked eddies. The distributions of all three measures of nonlinearity are more skewed toward large values for cyclonic eddies than for anticyclonic eddies in the southern hemisphere extratropics but the opposite is found in the northern hemisphere extratropics. There is thus a preference for highly nonlinear extratropical eddies to be cyclonic in the southern hemisphere but anticyclonic in the northern hemisphere.Further evidence in support of the interpretation of the observed features as nonlinear eddies is the fact that they propagate nearly due west with small opposing meridional deflections of cyclones and anticyclones (poleward and equatorward, respectively) and with propagation speeds that are nearly equal to the long baroclinic Rossby wave phase speed. These characteristics are consistent with theoretical expectations for large, nonlinear eddies. While there is no apparent dependence of propagation speed on eddy polarity, the eddy speeds relative to the local long Rossby wave phase speeds are found to be about 20% faster in the southern hemisphere than in the northern hemisphere. The distributions of the propagation directions of cyclones and anticyclones are essentially the same, except mirrored about a central azimuth angle of about 1.5° equatorward. This small, but we believe statistically significant, equatorward rotation of the central azimuth may be evidence of the effects of ambient currents (meridional advection or the effects of vertical shear on the potential vorticity gradient vector) on the propagation directions of the eddies.While the results presented here are persuasive evidence that most of the observed westward-propagating SSH variability consists of isolated nonlinear mesoscale eddies, it is shown that the eddy propagation speeds are about 25% slower than the westward propagation speeds of features in the SSH field that have scales larger than those of the tracked eddies. This scale dependence of the propagation speed may be evidence for the existence of dispersion and the presence of features that obey linear Rossby wave dynamics and have larger scales and faster propagation speeds than the nonlinear eddies. The amplitudes of these larger-scale signals are evidently smaller than those of the mesoscale eddy field since they are not easily isolated from the energetic nonlinear eddies. 相似文献
17.
南海及西北太平洋卫星高度计资料分析:海洋中尺度涡统计特征 总被引：4，自引：0，他引：4
采用AVISO提供的卫星高度计融合数据,对南海及西北太平洋(5°～35°N,105°～150°E)1993～2009年17a间的中尺度涡活动进行统计分析.结果表明南海中尺度涡活动具有明显的年际变化,每年观测到产生的中尺度涡个数平均为21～22个,标准差约为4个,占年平均值的20%;而西北太平洋中尺度涡个数的年际差异不大,平均每年观测到150～151个中尺度涡产生,标准差约为14个,仅占年平均值的9%.中尺度涡的逐月统计结果表明南海和西北太平洋的中尺度涡活动均有明显季节变化,1993～2009年间的各月南海和西北太平洋分别观测到30～31个和213～214个中尺度涡产生,标准差分别约为6个和41个,均占各自月平均值的19%.中尺度涡主要集中分布在南海东北部、越南东部和黑潮流轴附近海域.涡动能、海面高度距平均方根以及涡度均方根的空间分布大致与涡旋个数分布一致,但在西北太平洋的低纬海区和黑潮延伸体区域则不甚吻合.在相同的涡旋判别标准下,西北太平洋低纬海区(5°～15°N)观测到的中尺度涡个数比中高纬海区要少得多. 相似文献
18.
南海北部中尺度反气旋涡的湍流混合空间分布特征 总被引：2，自引：0，他引：2
文章利用GHP细结构参数化方法和Thorpe-scale方法，分析水下滑翔机于2015年5月在南海北部采集的数据，估算了南海北部中尺度反气旋涡的湍流混合空间分布特征。结果显示该反气旋涡的混合具有明显的空间非对称性，混合率在其运动方向的后侧边缘明显增强达到O(10-3 m2/s)量级；而在其运动方向的前侧边缘，平均混合率要小一个量级。这一混合非对称特征与中尺度的涡动能密切相关性。中尺度涡后侧边缘处存在高流速剪切，容易引起垂向剪切不稳定，可能是引起该处混合增强的主要因素。另外，中尺度涡后侧边缘发展的次中尺度过程同样导致了该处强混合。本研究结果有助于人们进一步认识南海北部的混合过程。 相似文献
19.
The eddy formation determined as an anticyclonic spin-off eddy of the Gulf Stream is analysed from the CTD data of surveys made in the Gulf Stream region. The differences in its structure and conditions of formation from cyclonic eddies of this type observed previously are examined. Barotropic instability of the Gulf Stream's main jet is considered as a possible reason for such unstable disturbances existing at the south boundary of the Gulf Stream.Translated by M. M. Trufanov. 相似文献
20.
孟加拉湾内和湾口附近有丰富的中尺度现象,本文利用2.0版可分辨低纬地区中尺度涡的Chelton数据集,通过溯源的方法得到中尺度涡的源地分布。苏门答腊岛西北海域(以5°N,94°E为核心的区域)是中尺度涡重要源区之一。通过拉格朗日方法的涡旋追踪表明,1993—2017年该海域(3°N—6°N、92°E—95°E),分别有57个气旋式和40个反气旋式中尺度涡。频谱分析显示海表面高度异常存在180 d和360 d两个显著周期。地形和风场的共同作用是该海域产生中尺度涡的动力机制：沿5°N西传的罗斯贝波在海岭地形的作用下触发了中尺度涡的生成;赤道风场是源区重要的能量来源,局地风场能诱发中尺度涡的极性。本研究也揭示了以往文献虽刻画了苏门答腊岛西北部海域为高涡动能区,却没有识别出较多中尺度涡的原因。 相似文献