Circulation in a Southern Italy coastal basin: Modelling and field measurements     

Francesca De Serio  Daniela Malcangio  Michele Mossa 《Continental Shelf Research》2007

The purpose of the present work is to study the hydrodynamic aspects in the Mar Piccolo, a coastal basin located on the northern side of the Gulf of Taranto in the Ionian Sea (Italy), by means of mathematical modelling and field measurements. The latter were assessed during three surveys carried out in the spring–summer of 2002. Collected data have been utilized as input by the 3-D Princeton Ocean Model, which is a sigma coordinate, free surface ocean model which was developed in the late 1970s by Blumberg and Mellor. Simulations in baroclinic condition were forced by a homogeneous and stationary wind field, a simple tidal wave, a constant outflow and vertical stratification of temperature and salinity. A comparison was made between the mathematical modelling results and the field measurements collected during the surveys, in terms of velocity. It was observed that during small tides, when the wind effect prevails over the stratification effect, the best model results were obtained for the most superficial layer and that superficial patterns reproduced by the model are more sensitive to wind direction than to stratification. On the contrary, when the wind effect decreases or the thermohaline effect rises, best results occurred in deeper layers.  相似文献   

On stochastic stability of regional ocean models to finite-amplitude perturbations of initial conditions   总被引：1，自引：0，他引：1  

Leonid M. Ivanov  Peter C. Chu 《Dynamics of Atmospheres and Oceans》2007,43(3-4):199-225

We consider error propagation near an unstable equilibrium state (classified as an unstable focus) for spatially uncorrelated and correlated finite-amplitude initial perturbations using short- (up to several weeks) and intermediate (up to 2 months) range forecast ensembles produced by a barotropic regional ocean model. An ensemble of initial perturbations is generated by the Latin Hypercube design strategy, and its optimal size is estimated through the Kullback–Liebler distance (the relative entropy). Although the ocean model is simple, the prediction error (PE) demonstrates non-trivial behavior similar to that existing in 3D ocean circulation models. In particular, in the limit of zero horizontal viscosity, the PE at first decays with time for all scales due to dissipation caused by non-linear bottom friction, and then grows faster than (quasi)-exponentially. Statistics of a prediction time scale (the irreversible predictability time (IPT)) quickly depart from Gaussian (the linear predictability regime) and becomes Weibullian (the non-linear predictability regime) as amplitude of initial perturbations grows. A transition from linear to non-linear predictability is clearly detected by the specific behavior of IPT variance. A new analytical formula for the model predictability horizon is introduced and applied to estimate the limit of predictability for the ocean model.  相似文献   

Paleoproductivity evolution off central Chile from the Last Glacial Maximum to the Early Holocene   总被引：1，自引：0，他引：1  

Oscar E. Romero  Jung-Hyn Kim  Dierk Hebbeln 《Quaternary Research》2006,65(3):519-525

A geochemical and paleontological reconstruction of paleoproductivity, upwelling intensity and sea surface temperature (SST) off central Chile at 35°S (GeoB3359-3) reveals marked changes from the Last Glacial Maximum (LGM) through the Early Holocene. Surface-water productivity was determined by the interaction between the atmospheric (the Southern Westerlies) and oceanographic (the Antarctic Circumpolar Current, ACC) systems from the LGM through early Termination I (TI). The northward shift of the climate zones during the LGM brought the ACC, as the main macronutrient source, closer to the GeoB3359-3, SST lowered, and surface water productivity and accumulation rates of biogenic components enhanced. With the poleward return of the Southern Westerlies and the ACC, the subtropical high-pressure system became the dominant atmospheric component southward till 35°S during the late TI and Early Holocene and caused surface water productivity to increase through enhanced upwelling.  相似文献   

A subtropical water intrusion spring-event in the shelf-slope of the south-western Bay of Biscay after strong wind-forcing pulses     

《Journal of Atmospheric & Ocean Science》2005,10(4):343-359

Two consecutive multidisciplinary surveys, covering the north and north-western part of the Iberian shelf and slope during spring 2000, showed a dramatic change in the oceanographic conditions as a result of a southern water intrusion that replaced shelf and slope waters down to 300 m depth. The intrusion covered an alongshore distance of ∼400 km from the north of Cape Finisterre to the centre of the Cantabrian Sea, and was developed in less than a month between the two occupations of the same area. The analysis of surface currents from several buoys moored over the slope allow us to associate the emerging oceanographic configuration after the event with a strong and well-defined slope current, although during winter 1999-2000 the entrance of the Iberian Poleward Current (IPC) in the Bay of Biscay was very weak. The rapid development of the intrusion is discussed in relation with the unusual strong wind forcing pulse that occurred between the cruises. Our results highlight the importance of variability scales below seasonal (event-scale) in the Iberian margin.  相似文献   

Variability of Currents off the Northern Coast of New Guinea     

Yoshifumi Kuroda 《Journal of Oceanography》2000,56(1):103-116

The variability of the New Guinea Coastal Current (NGCC) and New Guinea Coastal Undercurrent (NGCUC) were examined from one year time series of current data from ADCP moorings at 2°S, 142°E and 2.5°S, 142°E. Change in the hydrographic structure induced by monsoonal wind forcing was also examined from hydrographic data along the 142°E covering consecutively two winter seasons and two summer seasons. The westward NGCUC was observed to persist year around. The annual mean depth of the current core was 220 m, the mean speed of the zonal component was 54 cm/s with a standard deviation of 15 cm/s at the 2.5°S site. Velocity fluctuations at 20–30 day period were observed year around. Seasonal reversal of the surface intensified NGCC was clearly observed. In the boreal summer characterized by the southeasterly monsoon, westward currents of over 60 cm/s were dominant in the surface layer. The warm, low-salinity layer thickened at this time and sloped down toward the New Guinea coast from the equator. This surface water accumulation may be caused by onshore Ekman drift at the New Guinea coast, combined with weak Ekman upwelling at the equator. In the boreal winter, an eastward surface current developed to 100 cm/s extending down to 100 m depth in response to the northwesterly monsoonal winds. Coastal upwelling was indicated in this season and the surface water accumulated at the equator due to Ekman convergence. Shipboard ADCP data indicated that the NGCUC intensified in boreal summer as the width and depth of the NGCUC increased.  相似文献   

1996年春季南黄海水文特征和水团分析   总被引：37，自引：8，他引：29  

邹娥梅  郭炳火  汤毓祥  李载学 《海洋学报》2000,22(1):17-26

利用中韩“黄海水循环动力学及物质输运”合作研究项目第一航次1996初春所获得的CTD资料描述了南黄海初春温、盐和密度的水平和垂直分布特征,分析了水团结构,并揭示了春季在34°～36°N,121°45'～124°E的南黄海西部水域的中层冷水现象。分析结果表明初春黄海暖流上表层开始向济州岛方向退缩,黄海底层冷水团首先在青岛外海形成。  相似文献   

东海西北部中层冷水特征的时空变化   总被引：1，自引：0，他引：1  

徐伯昌  王宗山  邹娥梅  廖启煜 《海洋科学进展》2000,18(2):1-7

根据1959～1996年3～6月水温资料,按30'×30'方区统计计算了东海西北部中层冷水的8个示性特征值,并绘制了平面分布图.分析结果表明,东海西北部中层冷水于3月出现,4月形成,5月达到盛期,6月消衰,其生消规律具有明显的季节性;其出现的海区为28°～31°N,124°E以西(即台湾暖流路径)海域,具有明显的地域性.示性特征的时-空分布变化反映出:在形成期,地域性表现充分;在消衰期,反映出中层冷水下方的台湾暖流对它的影响明显;而在盛期,示性特征则为上述的过渡型.这为探讨海洋热、动力因子对其生消机制的影响奠定了实验基础.  相似文献   

渤海、黄海、东海冬季海流场温度场数值模拟和同化技术   总被引：6，自引：0，他引：6  

赵骞  田纪伟  曹丛华  王强 《海洋学报》2005,27(1):1-6

利用NASA高分辨率的卫星遥感资料SST,采用Nudging同化来模拟渤海、黄海、东海的三维温度场,减小用热通量作上边界条件所带来的误差.结果表明,模拟的海流场能较好地反映渤海、黄海、东海的环流特征.数据同化后的温度场优于未经同化的温度场.3个选择站点的同化值与实测值的均方根误差分别为1.307,0.526,0.744,用热通量资料模拟的水温与实测值的均方根误差分别为2.160,0.979,1.330.尽管只同化了海表温度,但数据同化对三维温度场结构都有影响.  相似文献   

Autumn intensification of the Ryukyu Current during 2003-2007   总被引：2，自引：0，他引：2  

ZHU Xiao-Hua  HUANG DaJi & GUO XinYu State Key Laboratory of Satellite Ocean Environment Dynamics  Second Institute of Oceanography  State Oceanic Administration  Hangzhou  China  Center for Marine Environmental Study  Ehime University  - Bunkyo-cho  Matsuyama -  Japan 《中国科学:地球科学(英文版)》2010,(4)

Inverse calculations using data from 16 repeat hydrographic transects collected from April 2003 to June 2007 have yielded velocity structures and volume transports(VTs) of the Ryukyu Current in the region east of the northern Ryukyu Islands.The inverse calculation results show that the Ryukyu Current is dominated by a subsurface velocity core with maximum velocities from 15.1 to 80.0 cm/s,whose positions vary between 110 and 600 dbar and 27.2°-28.2°N along the transect.The mean velocity exhibits a subsurface velocity core with a maximum value of 24.6 cm/s at 326 dbar depth,a VT of 14.0 Sv(1 Sv≡106 m3/s),a vertical dimension of 800 m,and a horizontal dimension of 60 km.The seasonal mean velocities show that the Ryukyu Current is stronger in autumn than in other seasons.It is suggested that this seasonal variation is coincident with the intensification of the anticyclonic eddy south of Shikoku,Japan.  相似文献   

黑潮入侵南海的强弱与太平洋年代际变化及厄尔尼诺-南方涛动现象的关系   总被引：2，自引：1，他引：1  

杨龙奇  许东峰  徐鸣泉  隋丹丹  吴品煌 《海洋学报》2014,36(7):17-26

在黑潮入侵南海强弱的问题上,到底是太平洋年代际变化(Pacific Decadal Oscillation,PDO)还是厄尔尼诺-南方涛动(El Nio-Southern Oscillation,ENSO)现象在起关键作用,目前还存在着较大争议。本文先以高盐水作为黑潮入侵强弱的示踪物,用120°E断面的高盐水数据和北赤道流分叉点(North Equator Current Bifurcation,NEC-Y)的南北变动进行相关分析,接着,进一步用学者所用的黑潮入侵指数(KI指数,Kuroshio intrusion index和NEC指数,North Equatorial Current index)与北赤道流分叉点南北变动进行相关分析。最后,用EMD(Empirical Mode Decomposition)方法和相关关系分析法分别分析了PDO指数、Nio3.4指数与北赤道流分叉点南北变动的关系并用NECP风场数据探讨其影响机制。结果表明:(1)通过对120°E断面的高盐水的KI指数、NEC指数与NEC-Y的相关分析,表明了北赤道流分叉点的南北变动能够很好地指代黑潮入侵南海的强弱;(2)通过PDO指数和Nio3.4指数与北赤道流分叉点的南北变动的相关性分析,发现PDO指数、Nio3.4指数与北赤道流分叉点的南北变动都具有较好的相关性,都在0.5水平。这些良好的相关性表明了PDO和ENSO对黑潮入侵南海的强弱都具有重要的影响;(3)当处于厄尔尼诺年(拉尼娜)时,赤道太平洋发生西(东)风异常,使得北赤道流分叉点偏北(南),使吕宋岛东侧的黑潮流速减弱(加强),黑潮入侵南海增强(减弱);当PDO处于暖(冷)阶段时,会加强热带太平洋的西(东)风异常,使得黑潮入侵南海增强(减弱)。  相似文献