南海上层中尺度涡统一三维结构   总被引：1，自引：0，他引：1  

郑堃  林霄沛  朱亚楠 《海洋与湖沼》2018,49(3):490-496

本文基于归一化合成分析的方法,利用卫星高度计资料和CTD观测资料,在满足静力平衡和地转平衡条件的假设下研究了南海中尺度涡的三维结构,给出了南海中尺度涡归一化之后的三维结构,并与全球大洋中尺度涡统一的三维结构进行对比。结果显示,在1.5倍涡旋半径以外,南海中尺度涡水平结构的收敛速度大约为全球大洋中尺度涡水平结构收敛速度的2.5倍,前者比后者的影响范围要小约1.5倍涡旋半径。由于数据原因,我们仅合成了南海0至800m水深中尺度涡的垂直结构,从垂直结构的合成结果来看,由于受到背景层结和科氏参数的影响,南海与全球大洋各海区中尺度涡的垂直结构具有明显的不同,随着深度的增加,南海中尺度涡垂直结构的衰减速度明显更快。  相似文献   

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  

胡冬  陈希  毛科峰  滕军  李妍  彭旭东 《海洋与湖沼》2018,49(3):497-511

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   

基于密度峰值聚类的中尺度涡轨迹自动追踪方法   总被引：1，自引：1，他引：0  

王辉赞  郭芃  倪钦彪  李佳讯 《海洋学报》2018,40(8):1-9

中尺度涡信息的提取包括涡旋的识别和轨迹追踪,其自动识别与追踪对于基于海量数据的中尺度涡分析十分重要。传统涡旋轨迹自动追踪方法一般需要预先设定搜索半径的阈值,存在一定的主观性。针对传统中尺度涡轨迹追踪方法存在的问题,论文从聚类的角度出发,提出基于密度峰值聚类算法实现对涡旋轨迹的自动追踪,并以南海中尺度涡追踪为例,将基于聚类的追踪算法与传统的相似度追踪算法进行比较分析。结果表明:（1）基于密度峰值聚类算法,可实现对海洋中尺度涡的自动追踪,该算法涡旋追踪准确率优于传统相似度算法;（2）该涡旋追踪算法对资料的完整性依赖度较低,特别是对于存在部分缺损数据的情况仍能较准确追踪;（3）该追踪算法克服了传统涡旋追踪算法需要预先设定搜索半径阈值的问题,自适应性更强。  相似文献   

Intercomparison of oceanic and atmospheric forced and coupled mesoscale simulations. Part I: Surface fluxes     

P. Josse  G. Caniaux  H. Giordani  S. Planton 《Annales Geophysicae》1999,17(4):566-576

A mesoscale non-hydrostatic atmospheric model has been coupled with a mesoscale oceanic model. The case study is a four-day simulation of a strong storm event observed during the SEMAPHORE experiment over a 500 × 500 km² domain. This domain encompasses a thermohaline front associated with the Azores current. In order to analyze the effect of mesoscale coupling, three simulations are compared: the first one with the atmospheric model forced by realistic sea surface temperature analyses; the second one with the ocean model forced by atmospheric fields, derived from weather forecast re-analyses; the third one with the models being coupled. For these three simulations the surface fluxes were computed with the same bulk parametrization. All three simulations succeed well in representing the main oceanic or atmospheric features observed during the storm. Comparison of surface fields with in situ observations reveals that the winds of the fine mesh atmospheric model are more realistic than those of the weather forecast re-analyses. The low-level winds simulated with the atmospheric model in the forced and coupled simulations are appreciably stronger than the re-analyzed winds. They also generate stronger fluxes. The coupled simulation has the strongest surface heat fluxes: the difference in the net heat budget with the oceanic forced simulation reaches on average 50 Wm⁻² over the simulation period. Sea surface-temperature cooling is too weak in both simulations, but is improved in the coupled run and matches better the cooling observed with drifters. The spatial distributions of sea surface-temperature cooling and surface fluxes are strongly inhomogeneous over the simulation domain. The amplitude of the flux variation is maximum in the coupled run. Moreover the weak correlation between the cooling and heat flux patterns indicates that the surface fluxes are not responsible for the whole cooling and suggests that the response of the ocean mixed layer to the atmosphere is highly non-local and enhanced in the coupled simulation.  相似文献   

Drifter observations of the Hebrides slope current and nearby circulation patterns     

M. Burrows  S. A. Thorpe 《Annales Geophysicae》1999,17(2):280-302

The mean flow at and around the Hebrides and Shetland Shelf slope is measured with ARGOS tracked drifters. Forty-two drifters drogued at 50 m were deployed in three circles over the Hebrides slope at 56.15°N in two releases, one on 5th December, 1995 and the second on 5–9th May, 1996. The circles span a distance of some 20 km from water depths of 200 m to 1200 m. Drifters are initially advected poleward along-slope by the Hebrides slope current at between 0.05 and 0.70 m s^–1 in a laterally constrained (25–50 km wide) jet-like flow. Drifters released in winter remained in the slope current for over 2000 km whilst summer drifters were lost from the slope current beyond the Wyville-Thomson Ridge, a major topographic feature at 60°N. Dispersion from the slope region into deeper waters occurs at bathymetric irregularities, particularly at the Anton Dohrn Seamount close to which the slope current is found to bifurcate, both in summer and winter, and at the Wyville-Thomson Ridge where drifters move into the Faeroe Shetland Channel. Dispersion onto the continental shelf occurs sporadically along the Hebrides slope. The initial dispersion around the Hebrides slope is remarkably sensitive to initial position, most of the drifters released in shallower water moving onto the shelf, whilst those in 1000 m or more are mostly carried away from the slope into deeper water near the Anton Dohrn Seamount. The dispersion coefficients estimated in directions parallel and normal to the local direction of the 500 m contour, approximately the position of the slope current core, are approximately 8.8 × 10³ m² s^–1 and 0.36 × 10³ m² s^–1, respectively, during winter, and 11.4 × 10³ m² s^–1 and 0.36 x 10³ m² s^–1, respectively, during summer. At the slope there is a minimum in across-slope mean velocity, Reynolds stress, and across-slope eddy correlations. The mean across-slope velocity associated with mass flux is about 4 × 10^–3 m s^–1 shelfward across the shelf break during winter and 2 × 10^–3 m s^–1 during summer. The drifters also sampled local patterns of circulation, and indicate that the source of water for the seasonal Fair Isle and East Shetland currents are the same, and drawn from Atlantic overflows at the Hebrides shelf.  相似文献   

Effects of Eddy Variability on the Circulation of the Japan/East Sea     

G. A. Jacobs  P. J. Hogan  K. R. Whitmer 《Journal of Oceanography》1999,55(2):247-256

The effect of mesoscale eddy variability on the Japan/East Sea mean circulation is examined from satellite altimeter data and results from the Naval Research Laboratory Layered Ocean Model (NLOM). Sea surface height variations from the Geosat-Exact Repeat Mission and TOPEX/POSEIDON altimeter satellites imply geostrophic velocities. At the satellite crossover points, the total velocity and the Reynolds stress due to geostrophic mesoscale turbulence are calculated. After spatial interpolation the momentum flux and effect on geostrophic balance indicates that the eddy variability aids in the transport of the Polar Front and the separation of the East Korean Warm Current (EKWC). The NLOM results elucidate the impact of eddy variability on the EKWC separation from the Korean coast. Eddy variability is suppressed by either increasing the model viscosity or decreasing the model resolution. The simulations with decreased eddy variability indicate a northward overshoot of the EKWC. Only the model simulation with sufficient eddy variability depicts the EKWC separating from the Korean coast at the observed latitude. The NLOM simulations indicate mesoscale influence through upper ocean-topographic coupling. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Inversion of the three-dimensional temperature structure of mesoscale eddies in the Northwest Pacific based on deep learning     

Fangjie Yu  Zeyuan Wang  Shuai Liu  Ge Chen 《海洋学报(英文版)》2021,40(10):176-186

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   

天宫二号近天底角交轨干涉SAR的海洋涡旋探测   总被引：1，自引：1，他引：0  

王宇航  种劲松 《遥感学报》2020,24(9):1070-1076

海洋涡旋是海洋科学研究的一个重要分支,在海洋热循环中起着重要的作用。传统的卫星高度计通常能够探测到水平尺度超过100 km的中尺度涡旋,但是由于其分辨率较为粗糙,对于1—100 km的亚中、小尺度涡旋难以探测。天宫二号搭载的三维成像微波高度计（InIRA）是国际上第1个可以用于进行海面高度测量的Ku波段干涉SAR,为观测和研究海洋亚中、小尺度涡旋提供了数据来源。InIRA不仅可以获取海洋涡旋2维SAR图像,同时通过两个天线获取复图像间的干涉相位,能够获取涡旋海表面高度异常,为海洋涡旋的探测研究提供了新的可能。本文基于天宫二号InIRA数据,开展了海洋涡旋探测的研究,提出一种通过计算涡旋海面相对高度变化实现海洋涡旋探测的方法。通过对InIRA涡旋数据的处理与分析,发现该方法能够实现海洋涡旋的探测,并利用MODIS叶绿素浓度数据和海表温度数据对海洋涡旋探测结果进行了验证。  相似文献   

中南半岛近海偶极子演变过程研究     

裘是  陈学恩  唐声全 《海洋与湖沼》2020,51(6):1332-1343

中南半岛近海偶极子结构是指在夏季与越南离岸流伴生的一对中尺度涡现象,其中气旋涡位于离岸流北侧,反气旋涡位于离岸流南侧,偶极子结构对于中南半岛近海水文要素具有重要影响。本文基于卫星高度计数据和HYCOM海洋模式的模拟结果,以2012年为例研究了该偶极子的演变过程,结果表明：偶极子结构7月出现,9月初鼎盛,10月消失;鼎盛时,两个涡旋直径均大于300km,在温跃层引起的最大位温异常可达±5℃。垂向结构上,反气旋涡呈中心对称,而气旋涡有非对称性,且影响深度大于反气旋涡。在200m以下,气旋涡有随深度增加向东倾斜的趋势,而反气旋涡有随深度增加向西偏移的趋势,但该趋势在200m层以上并不显著。对偶极子涡旋区域进行能量分析,结果表明偶极子能量主要来自于越南离岸流提供的正压和斜压能量,即越南离岸流区域是偶极子结构的主要能量源,局地风场对偶极子结构的维持也具有重要作用。能量既可以由离岸流输送给涡旋,也可以从涡旋向离岸流转化,但总体上是离岸流向涡旋提供能量。  相似文献   

Surface current patterns in front of the Venice Lagoon     

Miroslav Gačić  Vedrana Kovačević  Simone Cosoli  Andrea Mazzoldi  Jeffrey D. Paduan  Isaac Mancero-Mosquera  Sadegh Yari 《Estuarine, Coastal and Shelf Science》2009

Surface patterns of the low-frequency current in a 20 × 30 km region in front of the Venice Lagoon were analysed from a 13-month-long HF radar data set. Surface circulation was related to prevalent wind regimes in the area and to the tidal flow through the lagoon inlet. Three different categories of wind-forcing were defined: bora (NE wind), sirocco (SE wind), and finally the category containing all other wind directions and calms (winds lower than 3 m/sec). Mean flow and vorticity spatial distributions were discussed for different wind conditions. The coastal area about 5 km wide is characterized by a flow field with maximum vorticity. Outside the coastal boundary layer the interior flow is part of the Adriatic basin-wide cyclonic circulation. Two counter-rotating vortices of the dimension of about 4–5 km were evidenced in the average flow field in front of the lagoon inlet (Malamocco inlet) in all situations except for the bora. The vortex-pair is probably associated with the tidal flow through the inlet. The bora wind induces a strong southward coastal jet detached from the coast by about 5 km homogenizing the flow and eliminating the dipole. The average coastal flow pattern in calm wind conditions was also analysed as a function of the strong inflow/outflow (currents in the inlet > 0.7 m s⁻¹) from the lagoon inlet. In both cases the vorticity pattern is similar, with the negative vorticity to the left of the inlet and positive to the right looking seaward.  相似文献