Kuroshio extension variability explored through assimilation of TOPEX/POSEIDON altimeter data into a quasi-geostrophic model     

Yousuke Nishihama  Motoyoshi Ikeda 《Journal of Oceanography》2007,63(6):879-895

Mesoscale features in the eastward extension of the Kuroshio were investigated using assimilation of TOPEX/POSEIDON (T/P) data into a three-layer quasi-geostrophic model. The T/P data exhibited an elongated state of the southern recirculation gyre in 1993–95 and 1997, between whose two periods the gyre had a contracted state in 1995–96. A few stationary eddies were located in the southern gyre during the contracted state. The baroclinic instability, which was indicated by the phase shift from the uppermost-to the lowest-layer anomalies toward the downstream side, was evident near the Kuroshio Extension (KE) path. Since the instability never appeared in the artificial model without bottom topography, the topographic barrier for the eastward flow in the lowest layer was a necessary condition for the instability. The instability synchronized with the transition in the western region of the KE axis from the elongated to the contracted states. This evolution was interpreted as if the baroclinic instability played some part in the KE states and was a trigger for the transition from the elongated to the contracted states.  相似文献   

南沙群岛海域水体漫衰减系数Kd(490)的特性研究   总被引：6，自引：1，他引：6  

张清凌  陈楚群  施平 《热带海洋学报》2003,22(1):9-16

对南沙群岛海区水体Kd(490）的特性进行了深入分析和探讨,研究结果表明：Kd（490）的垂直分布与同步测量的海水叶绿素a浓度的垂直分布有很强的相关性;Kd（490）的垂直分布反映出该区域海水存在较强的分层现象,研究中还发现上行辐亮度漫衰减系数KL（490）与Kd（490）垂直变化趋势相当一致,但是以二者达到最大值的深度为界,上层水体的KL（490）值稍大于Kd(490）值,在这一深度以下则相反。  相似文献   

Relationship between Cd and PO4 in the Subtropical Sea near the Ryukyu Islands     

Kazuo Abe 《Journal of Oceanography》2002,58(4):577-588

The relationship between dissolved cadmium (Cd) and phosphate (PO₄) was examined at three stations in the subtropical area near the Ryukyu Islands in May 1999. Preformed PO₄ was obtained using the Redfield ratio in order to separate the surface water and the other layers in this study area. Almost 0 μM (−0.043 μM to 0.094 μM) was estimated in the layers above 300 m and 250 m at Sts. 1 and 3 and at St. 2, respectively. Up to these depths, water was considered to be uniform, and these layers were defined as the surface water in this study area. In the surface water, the slopes of the regression lines of the Cd-PO₄ plot were 0.162, 0.156, and 0.226 (nM/μM) at Sts. 1, 2, and 3, respectively, and these values were much closer to the estimated regenerated ratio of Cd to PO₄ from the Apparent Oxygen Utilization (AOU)-Cd/PO₄ plots, which was 0.197 (nM/μM) in this study area. Below surface layers, the slopes of the Cd-PO₄ plot changed to 0.371, 0.352, and 0.362 (nM//μM) at Sts. 1, 2, and 3, respectively. In the relationships between Cd and PO₄, clear deviations or kinks were observed at three stations at a PO₄ concentration of approximately 0.2 μM in the plot, which was attributable to the discontinuity of surface water and the other layers across the North Pacific subtropical mode water. In studies of the interaction between surface water and biogenic particles concerning the Cd/PO₄ ratio, separate analyses of seawater (surface water and the other layers) should be carried out to obtain the individual surface water ratio because the Cd/PO₄ ratio in the surface water is expected to differ from that of the underlying water. Furthermore, the biological fractionation of these constituents is based on the surface water ratio. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Annual Anthropogenic Carbon Transport into the North Pacific Intermediate Water through the Kuroshio/Oyashio Interfrontal Zone: An Estimation from CFCs Distribution     

Tsuneo Ono  Yutaka W. Watanabe  Katsuyuki Sasaki 《Journal of Oceanography》2000,56(6):675-689

Vertical distribution of anthropogenic carbon content of the water (exDIC) in the Oyashio area just outside of the Kuroshio/Oyashio Interfrontal Zone (K/O Zone) was estimated by the simple 1-D advection-diffusion model calibrated by the distribution of chlorofluorocarbons (CFCs). The average concentration of exDIC for = 26.60–27.00 is multiplied by the volume transport of Oyashio water into the North Pacific Intermediate Water (NPIW) to estimate the annual transport of exDIC into NPIW through K/O Zone. The estimated transport of exDIC was 0.018–0.020 GtC/y, which corresponds to 15% of the whole total exDIC accumulation in the temperate North Pacific. A simple assessment using the NPIW 1-box model indicates that the current study explains at least 70% of the total annual transport of exDIC into NPIW, and that small exDIC sources for NPIW still exists in addition to K/O Zone.  相似文献   

一种带自由面的三维船体贴体网络的数值生成     

李廷秋  缪国平  刘应中 《海洋工程》1996,(1)

本文提出了一个生成自由面的三维船体贴体网格的数值方法。文中以静水面以上的船体型线作为描述非定常自由面的计算网格域，进一步完善了我们以往开发的无法考虑兴波与静水面以上的船体型线相互作用对船舶粘性流动影响的网格生成方法。静水面以上的初始自由面网格分别沿船面法线η及切线ζ方向的曲线长的指数进行分布，即可极方便地调节自由面在船面及静水面附近的网格间距，也保证了在数值离散三维Ｐｏｉｓｓｏｎ方程时具有相当好的收敛性。这种方法的特点是计算量相当小，尤其能极方便地控制网格在船面簿粘性层中及静水面附近的分布。以Ｓｅｒｉｅｓ６０船模作为计算算例，带自由面的网格分布是相当满意的  相似文献   

High Precision Geoid Models HKGEOID-2000 for Hong Kong and SZGEOID-2000 for Shenzhen, China     

Zhicai Luo  Jinsheng Ning  Yongqi Chen  Zhanji Yang 《Marine Geodesy》2005,28(2):191-200

High precision geoid models HKGEOID-2000 for Hong Kong and SZGEOID-2000 for Shenzhen, China, have been developed with a hybrid approach of so-called sequential processing, using high precision GPS/leveling data, land and sea gravity anomalies, and digital terrain models. These two local geoid models have the same 1-km resolution. The estimated accuracy (external accuracy) is better than 1.7 cm for HKGEOID-2000 and 1.4 cm for SZGEOID-2000. Some common areas are covered by HKGEOID-2000 and SZGEOID-2000. So these two geoid models, along with high quality GPS/leveling data collected on the overlapping areas, can be used to detect the systematic bias between HKGEOID-2000 and SZGEOID-2000, as well as the difference between Hong Kong Principal Datum and 1956 yellow sea height datum of China, yielding RMS errors of 1.011 m and 1,003 m, respectively. Moreover, HKGEOID-2000, along with GPS ellipsoidal heights, is employed to determine the errors of the “orthometric heights” from purely trigonometric heighting, yielding an RMS error of 0.102 m. The combination of SZGEOID-2000 and GPS ellipsoidal heights has been used to replace the traditional spirit leveling and mapping, called GPS mapping.  相似文献   

Effect of strong winds on the nutritional condition of anchovy (Engraulis encrasicolus L.) larvae in the Bay of Biscay, Northeast Atlantic, as inferred from an early field application of the DNA/C index     

Bergeron  Jean-Pierre 《ICES Journal of Marine Science》2000,57(2):249-255

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Observations of the Labrador Sea eddy field   总被引：2，自引：0，他引：2  

Jonathan M. Lilly  Peter B. RhinesFriedrich Schott  Kara LavenderJohn Lazier  Uwe SendEric D’Asaro 《Progress in Oceanography》2003,59(1):75-176

This paper is an observational study of small-scale coherent eddies in the Labrador Sea, a region of dense water formation thought to be of considerable importance to the North Atlantic overturning circulation. Numerical studies of deep convection emphasize coherent eddies as a mechanism for the lateral transport of heat, yet their small size has hindered observational progress. A large part of this paper is therefore devoted to developing new methods for identifying and describing coherent eddies in two observational platforms, current meter moorings and satellite altimetry. Details of the current and water mass structure of individual eddy events, as they are swept past by an advecting flow, can then be extracted from the mooring data. A transition is seen during mid-1997, with long-lived boundary current eddies dominating the central Labrador Sea year-round after this time, and convectively formed eddies similar to those seen in deep convection modeling studies apparent prior to this time. The TOPEX / Poseidon altimeter covers the Labrador Sea with a loose “net” of observations, through which coherent eddies can seem to appear and disappear. By concentrating on locating and describing anomalous events in individual altimeter tracks, a portrait of the spatial and temporal variability of the underlying eddy field can be constructed. The altimeter results reveal an annual “pulsation” of energy and of coherent eddies originating during the late fall at a particular location in the boundary current, pinpointing the time and place of the boundary current-type eddy formation. The interannual variability seen at the mooring is reproduced, but the mooring site is found to be within a localized region of greatly enhanced eddy activity. Notably lacking in both the annual cycle and interannual variability is a clear relationship between the eddies or eddy energy and the intensity of wintertime cooling. These eddy observations, as well as hydrographic evidence, suggest an active role for boundary current dynamics in shaping the energetics and water mass properties of the interior region.  相似文献   

Geographic variability in trace element levels in Spartina alterniflora     

J.E. Drifmeyer  B. Redd 《Estuarine, Coastal and Shelf Science》1981,13(6):709-716

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Relationship between Shot-Induced Noise and Shot Interval in Seismic Refraction Experiments at Sea     

Herber  R.  Weigel  W.  Wong  H. K. 《Marine Geophysical Researches》1997,19(3):257-265

Seismic noise induced by the seismic source during continuous profiling reduces the signal-to-noise ratio and hence the data quality. This noise is largely dependent on the shot interval. In this paper, the noise amplitude of refraction seismic records from a special experiment is analysed as a function of the shot interval. An empirical exponential relationship between mean peak noise amplitude and shot interval is deduced. By increasing the shot interval, the induced noise can be minimized on all successive records. This results in an improvement of the data, predominantly the signal-to-noise ratio. Because the seismic signal and the shot-induced noise have nearly the same spectra, the chance of improving the signal-to-noise ratio by stacking is significantly reduced.  相似文献