南海中尺度涡的演化过程与行为追踪:一种基于全局最邻近滤波的方法     

易嘉伟  杜云艳  王东晓  周成虎 《海洋学报(英文版)》2017,36(11):27-37

The eddy tracking approach is developed using the global nearest neighbor filter(GNNF) to investigate the evolution processes and behaviors of mesoscale eddies in the South China Sea(SCS). Combining the Kalman filter and optimal data association technologies, the GNNF algorithm is able to reduce pairing errors to 0.2% in tracking synthetic eddy tracks, outperforming other existing methods. A total of 4 913 eddy tracks that last more than a week are obtained by the GNNF during 1993–2012. The analysis of a growth and a decay based on 3 445 simple eddy tracks show that eddy radius, amplitude, and vorticity smoothly increase during the first half of lifetime and decline during the second half following a parabola opening downwards. The genesis of eddies mainly clusters northwest and southwest of Luzon Island whereas the dissipations concentrate the Xisha Islands where the underwater bay traps and terminates eddies. West of the Luzon Strait, northwest of Luzon Island, and southeast of Vietnam are regions where eddy splits and mergers are frequently observed. Short disappearances mainly distribute in the first two regions. Moreover, eddy splits generally result in a decrease of the radius and the amplitude whereas eddy mergers induce growing up. Eddy intensity and vorticity, on the contrary, are strengthened in the eddy splits and diminished in mergers.  相似文献   

南海潜热交换年际与年代际变化的分析探讨     

隋丹丹  谢强  王东晓 《海洋学报(英文版)》2012,31(4):27-34

根据一套客观分析潜热通量、基于绕岛理论诊断的南海贯穿流(LST)、南海热含量等月平均资料,分析南海表层潜热通量的年际和年代际变化特征。南海地区的潜热通量冬季强,春季的潜热通量弱;在秋冬季节,南海北部的潜热通量远大于南部;夏季南海潜热通量南部高于北部;从20世纪80年代初潜热通量逐渐增加。使用EOF经验正交分解,M-K检验方法分析南海潜热通量的多时间尺度变化,前3个模态的方差贡献率分别为:53.01%(主要为长期趋势)、17.4%(年代际变化)、6.71%(年际变化)。分析表明在年际尺度上南海贯穿流(LST)减少导致南海海表温度(SST)增温幅度上升,海气温差比湿差减小,从而导致潜热释放减少,潜热通量呈负异常;反之LST进入南海增多,海气温差比湿差变大,导致南海潜热损失减少,潜热通量呈正异常。  相似文献   

Anticyclonic eddies in the northeastern South China Sea during winter 2003/2004   总被引：10，自引：1，他引：9  

Dongxiao Wang  Hongzhou Xu  Jing Lin  Jianyu Hu 《Journal of Oceanography》2008,64(6):925-935

The origins and evolutions of two anticyclonic eddies in the northeastern South China Sea (SCS) were examined using multi-satellite remote sensing data, trajectory data of surface drifting buoys, and in-situ hydrographic data during winter 2003/2004. The results showed that buoy 22918 tracked an anti-cyclonic warm-core eddy (AE1) for about 20 days (December 4–23, 2003) in the northeastern SCS, and then escaped from AE1 eventually. Subsequently to that, buoy 22517 remained within a different anti-cyclonic warm-core eddy (AE2) for about 78 days (from January 28 to April 14, 2004) in the same area. It drifted southwestward for about 540 km, and finally entered into the so-called “Luzon Gyre”. Using inference from sea level anomaly (SLA), sea surface temperature (SST), geostrophic currents and the buoys’ trajectories, it is shown that both eddies propagated southwestward along the continental slope of the northern SCS. The mean speeds of AE1 and AE2 movements were 9.7 cm/s and 10.5 cm/s, respectively, which are similar to the phase speed of Rossby waves in the northern SCS. The variation of instantaneous speeds of the eddy movement and intensity of anticyclonic eddy may suggest complex interactions between an anticyclonic eddy and its ambient fluids in the northern SCS, where the eddy propagated southwestward with Rossby waves. Furthermore, SLA and SST images in combination with the temperature and salinity profiles obtained during a cruise suggested that AE1 was generated in the interior SCS and AE2 was shed from the “Kuroshio meander”.  相似文献   

A survey of baroclinic tides in the Beibu Gulf in the South China Sea   总被引：1，自引：1，他引：0  

CHEN Ju  WANG Dongxiao  SHI Ping  DU Yan 《海洋学报(英文版)》2007,26(4):7-19

The principal characteristics of the tides are investigated by a shipborne acoustic Doppler current Profiler at a fixed station located in the Beibu Gulf from 4 to 14 April 2003. Data analysis indicates that the diurnal tidal currents dominate local current variations at the observing site. Except the barotropic M_2 constituent, four principal tides comprise both back-and-forth barotropic and baroclinic tidal currents. The baroclinic tidal ellipse parameters vary with depth, showing complicate features, rather than monotonous features being figured. For baroclinic tidal constituents, vertical modes are different to each other. Similarly, the semi-major axes of the tidal constituents vary with depth. In the lower layer, a nonlinear regression approach is used to calculate and obtain the SEMA profiles of diurnal tidal constituents. Results show that in the thin bottom boundary layer, all of the parameters vary drastically with depth, totally distinguished from the vertical profiles above.  相似文献   

印度洋-太平洋海温的年际、年代际异常及其对亚洲季风的影响   总被引：26，自引：5，他引：26  

徐建军  王东晓 《海洋学报》2000,22(3):34-43

运用EOF分析方法,对近50a的印度洋-太平洋SST的年际、年代际变化特征进行了分析,并在此基础上进行了数值试验.研究表明:在近50a中,SST的第一气候模态与年代际尺度变化相对应,并经历了两次气候突变,分别在1956年和1976年前后.第二气候模态与ENSO事件相对应,其空间分布反映了厄尔尼诺发生时SST的异常分布.中国东部降水以及亚洲季风异常不仅与ENSO事件有关,而且受到年代际气候背景场的影响.诊断和模拟结果具有较好的一致性.  相似文献   

南海表层水温年际变化的大尺度特征   总被引：22，自引：2，他引：22  

王卫强  王东晓  齐义泉 《海洋学报》2000,22(4):8-16

通过对COADS海洋气象资料的分析,得出南海表层水温(SST)年际变化的若干大尺度特征.结果表明:南海SST年际具有一定的准周期性,其显著周期为24～30个月;南海SST年际变化与年循环之间有着一种锁相关系,关键位相在于北半球冬春季节;南海典型冷暖年份合成SST距平场的时空结构十分相似;在年际时间尺度上,南海SST和南方涛动指数有反相关系,与经向风海面热收支之间有同位相关系;南海暖池面积指数的年际变化与南海SST年际变化一致.  相似文献   

A case study of near-inertial oscillation in the South China Sea using mooring observations and satellite altimeter data   总被引：9，自引：0，他引：9  

Lu Sun  Quanan Zheng  Dongxiao Wang  Jianyu Hu  Chang-Kuo Tai  Zhenyu Sun 《Journal of Oceanography》2011,67(6):677-687

A near-inertial oscillation (NIO) burst event in the west South China Sea (SCS) was observed by an upward-looking mooring Acoustic Doppler Current Profiler (ADCP) in summer 2004. The mooring station was located at 13.99°N, 110.52°E. The spectral analysis reveals that typhoon Chanchu is a major mechanism in triggering the NIO burst event. Before typhoon Chanchu passed over, the NIO signals were quite weak. The NIO band becomes the most energetic constituent of the circulation during the typhoon-wake period. The average peak power density (PD) reaches (5.3 ± 2.6) × 10² cm² s⁻² (cycles per hour, cph)⁻¹ with a maximum value of 9.0 × 10² cm² s⁻² cph⁻¹, i.e., 3.1 times higher than that of diurnal tide (DT), (1.7 ± 0.5) × 10² cm² s⁻² cph⁻¹. At the upper (80 m) and sub-upper (208 m) layers, the central frequency of the NIO band is 0.022 cph with a blueshift of about 9% above the inertial frequency f (0.02015 cph). At the lower layer (400 m), the central frequency of the NIO band is 0.021 cph with a blueshift of about 4% above the inertial frequency. The blueshifts are explained partially by the Doppler shift induced by the vorticity of mesoscale eddies. During the after-typhoon period, a resonance-like process between NIO and DT is observed in the upper layer. As the NIO frequency approaches the DT subharmonic frequency (0.5K₁), the PD of the NIO band rises sharply accompanied by a sharp drop of the PD of the DT band. The PD ratio of the two bands increases from 4.5 during the typhoon-wake period to 8 during the after-typhoon period, indicating the effect of the parametric subharmonic instability (PSI) mechanism.  相似文献   

The characteristic differences of tropical cyclones forming over the western North Pacific and the South China Sea   总被引：5，自引：1，他引：4  

YUAN Jinnan  WANG Dongxiao  LIU Chunxi  HUANG Jian  HUANG Huijun 《海洋学报(英文版)》2007,26(4):29-43

The best track dataset of tropical cyclones in the western North Pacific (WNP) and the South China Sea (SCS) from 1977 to 2005 during the satellite era, the NCEP/NCAR reanalysis dataset and the extended reconstructed sea surface temperature dataset are employed in this study. The main climatological characteristics of tropical cyclone formation over the WNP and the SCS are compared. It is found that there is obviously different for the locations of tropical cyclone origins, achieving the lowest central pressure and termination points between over the WNP and over the SCS. The annual number of tropical cyclones forming over the SCS is obviously less than over the WNP, and there is a significant negative correlation with the correlation coefficient being -0.36 at the 5% significance level between over the WNP and over the SCS. The mean speed of tropical cyclone moving is 6.5 m /s over the WNP and 4.6 m /s over the SCS. The mean lowest central pressure of tropical cyclones is obviously weaker over the SCS than over the WNP. The tropical cyclone days per year, mean total distance and total displacement of tropical cyclone traveled over the WNP are all obviously longer than those over the SCS. Tropical cyclone may intensify to Saffir-Simpson hurricane scale 5 over the WNP, but no tropical cyclone can intensify to Saffir-Simpson hurricane scale 3 over the SCS. The changing ranges of the radii(R15,R16) of the 15.4 m /s winds them and the 25.7 m /s winds over the WNP are obviously wider than those over the SCS, and the median values of the radii over the WNP are also larger than those over the SCS. For the same intensity of tropical cyclones, both radii have larger medians over the WNP than over the SCS. The correlations of annual mean tropical cyclone size parameters between over the WNP and over the SCS are not significant. At the same time, the asymmetric radii of tropical cyclones over the WNP are different from those over the SCS.  相似文献   

A three-dimensional modeling study on eddy-mean flow interaction between a Gaussian-type anticyclonic eddy and Kuroshio   总被引：1，自引：0，他引：1  

Wu Geng  Qiang Xie  Gengxin Chen  Qinyan Liu  Dongxiao Wang 《Journal of Oceanography》2018,74(1):23-37

The Princeton ocean model is employed to study the energy balance of a fast-moving anticyclonic eddy (AE) during eddy-mean flow interaction. The AE is initialized with an axisymmetric Gaussian-type temperature profile and is placed to the east of the Philippine Islands. An energy analysis suggests that the advection term, pressure work and friction term play dominant roles in the initial eddy decay. During the strong interaction stage, barotropic instability (BTI) becomes the main force for the eddy kinetic energy (EKE) production, with the largest positive BTI in the interaction zone, which means that the eddy always obtains kinetic energy from the Kuroshio during this stage. Most of the EKE dissipation, the large conversion from the eddy available potential energy to the EKE and that from the mean kinetic energy to the EKE all occur at the upper layer during the strong interaction stage. When the AE interacts with the mean flow on the eastern side of the Kuroshio, whether the AE gains kinetic energy from the Kuroshio or loses kinetic energy to the Kuroshio is mainly determined by its shape in the interaction zone.  相似文献   

Role of wind forcing and eddy activity in the intraseasonal variability of the barrier layer in the South China Sea     

Zhanlin Liang  Qiang Xie  Lili Zeng  Dongxiao Wang 《Ocean Dynamics》2018,68(3):363-375

In addition to widely discussed seasonal variability, the barrier layer (BL) of the South China Sea (SCS) also exhibits significant intraseasonal variability (ISV) and plays an important role in the upper heat and salt balances. The characteristics and mechanisms of spatiotemporal variations in the BL are investigated using an eddy-resolving ocean model OFES (OGCM For the Earth Simulator) ouput and related atmospheric and oceanic processes. The active intraseasonal BL variability in the SCS occurs mainly during the late summer/autumn and winter and exhibits remarkable differences between these two periods. The BL ISV in late summer/autumn occurs in the southern basin, while in winter, it is limited to the northwestern basin. To further discuss the evolution and driving thermodynamic mechanisms, we quantify the processes that control the variability of intraseasonal BL. Different mechanisms for the intraseasonal BL variability for these two active periods are investigated based on the case study and composite analysis. During late summer/autumn, the active BL in the southern basin is generated by advected and local freshwater, and then decays rapidly with the enhanced wind. In winter, anticyclonic eddy activity is associated with the evolution of the BL by affecting the thermocline and halocline variations, while wind stress and wind stress curl have no obvious influence on BL.  相似文献