Operational Data Assimilation System for the Kuroshio South of Japan: Reanalysis and Validation   总被引：3，自引：5，他引：3  

Masafumi Kamachi  Tsurane Kuragano  Hiroshi Ichikawa  Hirohiko Nakamura  Ayako Nishina  Atsuhiko Isobe  Daisuke Ambe  Masazumi Arai  Noriaki Gohda  Satoshi Sugimoto  Kumi Yoshita  Toshiyuki Sakurai  Francesco Uboldi 《Journal of Oceanography》2004,60(2):303-312

We describe an operational ocean data assimilation system for the Kuroshio and its validation using a nine-year reanalysis (historical run from 1993 to 2001) dataset of upper-ocean state estimation in the North Pacific. The horizontal structure of volume transport of the Ryukyu Current System (RCS) is shown from the reanalysis: The RCS is connected to the flow of the subtropical gyre, and its volume transport gradually increases from south-east of Okinawa (5–10 Sv) to the east of Amami-Ohshima Island (20 Sv). Comparing the reanalysis with independent observations on the southeast slope of the Amami-Ohshima Island indicates that the root mean square differences (RMSDs) are 0.076 (0.037) m/s in the period of December 1998 to November 1999 (November 1999 to November 2000) respectively. The reanalysis field has a bias (3.1 Sv) of the volume transport of the RCS and the RMSD (3.5 Sv) which is larger than the observed variability (2.81 Sv). Surface velocity and the Kuroshio axis south of Japan are also examined. Comparison of the reanalysis and ADCP data gave maximum RMSD of 0.749 (0.271) m/s in the strong (weak) current regions, respectively. The annual mean value of the axis error is 19 km in 1998. The RMSD of the error is at most 50 km, in 294 cases in the observation period, which is smaller than the observed root mean square variability of the axis (64 km). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Measurement and evaluation of the hydrodynamics and secondary currents in and near a strait connecting large water bodies—A field study     

I&#x;khan Güler  Yal&#x;n Yüksel  Ahmet Cevdet Yal&#x;ner  Esin evik  Christian Ingerslev 《Ocean Engineering》2006,33(13):1718-1748

The straits connect two large water bodies show highly strong and stratified currents related to meteorological, morphological and hydrodynamic conditions. In some cases, spatial and temporal changes of the stratified currents and their thickness, direction and magnitude are so complex. This complexity directly affects the circulation pattern in the region, water exchange between both ends of the straits and migration of fish species. In order to understand general characteristics of this kind of straits and identifying the complexity of the hydrodynamics of the region and evaluate the secondary currents and recirculation need long term, intensive, field work and measurement studies. As an example of this kind of hydrodynamically complex straits, Bosphorus strait is selected for a field study. The Bosphorus strait has a strongly stratified two-layer system and a unique case of the maximal exchange regime typical of strait flows, which is largely determined by conditions at the Black Sea. Although the Bosphorus strait has distinct two-layer stratification with an associated two-layer system exchange, no continuous current measurements have been made so far, previous measurements all having been random sampling.In this paper, a detailed measurement program has been applied to Bosphorus strait. In the measurement program, a short-term current profile measurement at selected locations at southern part of the strait has been conveyed. Additionally a long-term measurement of current profile has been performed at a selected critical location (in front of the Dolmabahçe Palace) where a recirculation flow exists in the strait. The scope of this paper is to present the techniques and the results of analysis of measurement data. In the measurements the current profile (magnitude and direction) has been determined at every 1 m depth intervals from the surface to the sea bottom at 3 min duration at every hour. Measurements provide that lower-layer flows in northward direction from the Sea of Marmara towards the Black Sea, whereas the upper-layer flow comes from the Black Sea and flows towards the Sea of Marmara in the opposite direction of lower layer. The Bosphorus strait exhibits distinctive features associated with variations in its width and depth. The meandering features of Bosphorus also cause recirculation flows. These results of measurements are presented, discussed and compared with previous studies.  相似文献   

末次盛冰期以来东海陆架南部EA05岩心地层划分及其古环境意义     

余华  刘振夏  熊应乾  李双林  向荣 《中国海洋大学学报(自然科学版)》2006,36(4):545-550

通过综合分析东海陆架南部EA05岩心上部30 m的岩性、有孔虫丰度和一些特征的地球化学参数,探讨了该段岩心的气候地层划分。该段岩心可依次划分为末次盛冰期(30~11.85 m)、冰消期(11.85~5 m)和冰后期(5~0 m)地层。末次盛冰期时气温低,研究区水深浅,沉积物中有孔虫丰度很低,且大多数热带浮游有孔虫种属消失,此时陆源物质输入量较大,沉积物中有机质含量高,黑潮对东海陆架南部影响小。随着冰消期以来气温回升,海面上升,研究区水深增大,岩心中有孔虫丰度急剧增加;陆源物质输入量减少,沉积速率降低。大约在16 ka B.P.左右,黑潮重新开始对东海南部陆架产生影响。在EA05岩心的6~5 m,3.4~3.0 m和1.4~1.2 m处分辨出了3个冷事件,可能分别对应于YD事件、8.2 ka B.P.冷事件和3.8 ka B.P.新冰期Ⅲ,反映出该地区冰消期和冰后期气候波动较大。  相似文献   

Velocity structures and transports of the Kuroshio and the Ryukyu current during fall of 2000 estimated by an inverse technique   总被引：7，自引：0，他引：7  

Xiao-Hua Zhu  Jae-Hun Park  Ikuo Kaneko 《Journal of Oceanography》2006,62(4):587-596

An inverse calculation using hydrographic section data collected from October to December 2000 yields velocity structure and transports of the Kuroshio in the Okinawa Trough region of the East China Sea (ECS) and south of central Japan, and of the Ryukyu Current (RC) southeast of the Ryukyu Islands. The results show the Kuroshio flowing from the ECS, through the Tokara Strait (TK), with a subsurface maximum velocity of 89 cm s⁻¹ at 460 dbar. In a section (TI) southeast of Kyushu, a subsurface maximum velocity of 92 cm s⁻¹ at 250 dbar is found. The results also show the RC flowing over the continental slope from the region southeast of Okinawa (OS) to the region east of Amami-Ohshima (AE) with a subsurface maximum velocity of 67 cm s⁻¹ at 400 dbar, before joining the Kuroshio southeast of Kyushu (TI). The volume transport around the subsurface velocity maximum southeast of Kyushu (TI) balances well with the sum of those in TK and AE. The temperature-salinity relationships found around these velocity cores are very similar, indicating that the same water mass is involved. These results help demonstrate the joining of the RC with the Kuroshio southeast of Kyushu. The net volume transport of the Kuroshio south of central Japan is estimated to be 64∼79 Sv (1 Sv ≡ 10⁶ m³s⁻¹), of which 27 Sv are supplied by the Kuroshio from the ECS and 13 Sv are supplied by the RC from OS. The balance (about 24∼39 Sv) is presumably supplied by the Kuroshio recirculation south of Shikoku, Japan.  相似文献   

东海黑潮区莹虾类的初步研究     

马兆党  宋庆云 《海洋科学进展》1992,(4)

1984年6月和1985年12月,对东海进行了首次黑潮实验性调查.整个调查区涉及到东海及东海黑潮区。作为综合调查项目其中之一的生物调查,在全调查区进行了取样:冬、夏两航次共采集浮游动物样品115份,经分析共鉴定出莹虾类4种。夏季(6月)出现中型莹虾 Luciferintermedius、正型莹虾 Lucifer typus、刷状莹虾 Lnckfer penicillifer、东方莹虾 Lucifer oriental-is;冬季(12月)出现中型莹虾 Lucifer intermedius、正型莹虾 Lucifer typus,可以明显地看出莹虾类的数量分布和种类分布与水温、营养盐、水团、流系等之间有密切的关系。并且莹虾类的数量分布与渔场的位置也有一定关系。据本次调查及资料分析,夏季可将中型莹虾作为东海混合水的指标种;正型莹虾可作为黑潮水的指标种;刷状莹虾可作为台湾暖流的指标种,为水文的调查提供较有价值的参考.  相似文献   

冲绳海槽南部玄武岩中的流体包裹体成分及其意义   总被引：1，自引：1，他引：1  

韩喜球  马维林  金翔龙  杨树锋  高金耀 《海洋与湖沼》2002,33(1):42-46

用激光拉曼探针分析了冲绳海槽南部橄榄拉斑玄武岩中的流体包裹体成分。结果表明，流体包裹体的主要成分为CO2，此外，还有H2O、H2S、CH4、N2、C2H2、C2H4、C3H8组分。不同宿主矿物，其包裹体成分中CO2、H2O和CH4的相对含量也不同，其中，钙长石中包裹体的CO2含量最高，贵橄榄石中的次之，普通辉石中的最少。CH4和H2O的含量趋势与CO2相反。根据这3种宿主矿物中流体成分及其含量变化特点，推断这3种宿主矿物的结晶顺序为钙长石、贵橄榄石、普通辉石，并认为流体包裹体中的烃类和水可能主要来自熔体上升过程中所接触的沉积地层。  相似文献   

Predicting the capability-polar-plots for dynamic positioning systems for offshore platforms using artificial neural networks   总被引：1，自引：0，他引：1  

Ayman B. Mahfouz   《Ocean Engineering》2007,34(8-9):1151-1163

As the capability of polar plots becomes better understood, improved dynamic positioning (DP) systems are possible as the control algorithms greatly depend on the accuracy of the aerodynamic and hydrodynamic models. The measurements and estimation of the environmental disturbances have an important role in the optimal design and selection of a DP system for offshore platforms. The main objective of this work is to present a new method of predicting the Capability-Polar-Plots for offshore platforms using the combination of the artificial neural networks (NNs) and the capability polar plots program (CPPP). The estimated results from a case study for a scientific drilling vessel are presented. A trained artificial NN is designed in this work and is able to predict the maximum wind speed at which the DP thrusters are able to maintain the offshore platform in a station-keeping mode in the field site. This prediction for the maximum wind speed will be a helpful tool for DP operators in managing station-keeping for offshore platforms in an emergency situation where the automation of the DP systems is disabled. It is obvious from the obtained results that the developed technique has potential for the estimation of the capability-polar-plots for offshore platforms. This tool would be suitable for DP operators to predict the maximum wind speed and direction in a very short period of time.  相似文献   

Spatial and Temporal Variability in a Vertical Section Across the Alaskan Stream and Subarctic Current   总被引：1，自引：0，他引：1  

Hiroji Onishi 《Journal of Oceanography》2001,57(1):79-91

In the central North Pacific Subarctic Gyre, CTD hydrographic measurements were carried out yearly in late June from 1990 to 1998 at 9 stations along 180° meridian from 48°N to 51.2°N. Vertical sections of 9-year means, anomalies for each year and others of potential temperature, salinity, potential density and geostrophic velocity (referred to 3000 m) were calculated based on this data set. Empirical Orthogonal Function (EOF) analysis was adopted in the investigation of spatial characteristics and its temporal variation in vertical sections. The spatial distribution of the 1st mode EOF of velocity shows the westward Alaskan Stream and the eastward Subarctic Current. This mode explains 37.6% of the total variance. Two positive maxims appear in its amplitude in 1991 and 1997, which is similar to the variation in volume transport of the eastward Subarctic Current. These variations are closely related to the vertical movement of Ridge Domain deep water.  相似文献   

Structure and Transport of the Agulhas Current and Its Temporal Variability     

Harry?L.?BrydenEmail author  Lisa?M.?Beal  Louise?M.?Duncan 《Journal of Oceanography》2005,61(3):479-492

Using a year-long moored array of current meters and well-sampled synoptic sections, we define the variability and mean structure and transport of the Agulhas current. Nineteen current meter records indicate that time scales for the temporal variability in the alongshore and offshore velocities are 10.2 and 5.4 days, respectively. Good vertical correlation exists between the alongshore or onshore velocity fluctuations, excluding the Agulhas Undercurrent. The lateral scale for the thermocline Agulhas current is about 60 km and the onshore velocity correlations are positive throughout the Agulhas Current system. Mean velocities from the array determine that the offshore edge of the Agulhas Current lies at 203 km and the penetration depth is 2200 m offshore of the Undercurrent. Hence, daily averaged velocity sections, determined by interpolation and extrapolation of current meter locations, for a 267-day period, from the surface to 2400 m depth and from the coast out to 203 km offshore encompass the main features of the Agulhas Current system. The Agulhas current is generally found close to the continental slope, within 31 km of the coast for 211 of 267 days. There are only five days when the core of the current is found offshore at 150 km. Total transport is always poleward, varying from −121 to −9 Sv, with maximum transport occurring when the core is 62 km from the coast. Average total transport for the 267 day period is −69.7 Sv; the standard deviation in daily transport values is 21.5 Sv; and the mean transport has an estimated standard error of 4.3 Sv. The Agulhas Undercurrent, which hugs the continental slope below the zero velocity isotach, has an average equatorward transport of 4.2 Sv, standard deviation of 2.9 Sv and an estimated standard error of 0.4 Sv. Transports from the moored array are in reasonable agreement with transport results from synoptic sections. Based on time series measurements at about 30° latitude in each ocean basin, the Agulhas Current is the largest western boundary current in the world ocean.  相似文献   

The East Greenland Current and its contribution to the Denmark Strait overflow   总被引：8，自引：1，他引：8  

Rudels  Bert; Fahrbach  Eberhard; Meincke  Jens; Budeus  Gereon; Eriksson  Patrick 《ICES Journal of Marine Science》2002,59(6):1133-1154

  相似文献