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   

距离观测方程参数估计的随机搜索法     

史德杰  孙远远  马克波  何冬晓  张胜伟 《北京测绘》2021,35(4):520-523

针对传统非线性模型参数估计方法(牛顿法、高斯-牛顿法、最速下降法、阻尼最小二乘法等)过度依赖初始值精度、只能获取局部最优解的缺点,利用遗传算法全局搜索能力的特点,得到距离观测方程参数估计解.最后利用短程测距数据和水下定位数据,验证了该算法的参数估计解.结果表明:该算法的收敛解优于线性平差估计解且明显提高解的精度.  相似文献   

Cloudiness regime shift during 1946-1992 recorded by coral in the South China Sea   总被引：1，自引：0，他引：1  

GAO Rongzhen  SUN Donghuai  WANG Dongxiao  YANG Xiaoyi 《海洋学报(英文版)》2005,24(5):27-34

1 IntroductionCorals from the tropical oceans are the well-known paleoclimate proxies that offer both the high-resolution and multi-century record length needed forquantification of seasonal to centennial variations.Most corals build skeletons of aragonite (CaCO3) andgrow at rates of millimeters to centimeters per year(Sun et al., 2002). During growth, annual densitybands are produced in the skeleton that shows timemarkers for the development of chronologies (seeFig.1). Coral skeletons may p…  相似文献   

南海表层水温低频振荡的基本特征   总被引：24，自引：3，他引：24  

于慎余  周发琇  傅刚  王东晓 《海洋与湖沼》1994,25(5):546-551

使用１９５８－１９８７年ＣＯＡＤＳ资料对南海全区表层水温做了分析。结果发现，南海表层水温存在２０－４０个月的低频振荡，其中以准两年周期最显著，其次是３－４年，这种振荡主要发生在深水海盆区，并且与季风异常有着十分密切的关系。  相似文献   

Decadal variability of the shallow Pacific meridional overturning circulation: Relation to tropical sea surface temperatures in observations and climate change models   总被引：6，自引：0，他引：6  

Dongxiao Zhang  Michael J. McPhaden 《Ocean Modelling》2006,15(3-4):250

In this study, we use existing observational datasets to evaluate 20th century climate simulations of the tropical Pacific. The emphasis of our work is decadal variability of the shallow meridional overturning circulation, which links the tropical and subtropical Pacific Ocean. In observations, this circulation is characterized by equatorward geostrophic volume transport convergence in the interior ocean pycnocline across 9°N and 9°S. Historical hydrographic data indicate that there has been a decreasing trend in this convergence over the period 1953–2001 of about 11 Sverdrup (1 Sv = 10⁶ m³ s⁻¹), with maximum decade-to-decade variations of 7–11 Sv. The transport time series is highly anti-correlated with sea surface temperature (SST) anomalies in the central and eastern tropical Pacific, implying that variations in meridional overturning circulation are directly linked to decadal variability and trends in tropical SST. These relationships are explored in 18 model simulations of 20th century climate from 14 state-of-the-art coupled climate models. Significant correlation exists between meridional volume transport convergence and tropical SST in the majority of the models over the last half century. However, the magnitude of transport variability on decadal time scales in the models is underestimated while at the same time modeled SST variations are more sensitive to that transport variability than in the observations. The effects of the meridional overturning circulation on SST trends in most the models is less clear. Most models show no trend in meridional transport convergence and underestimate the trend in eastern tropical Pacific SST. The eddy permitting MIROCH model is the only model that reasonably reproduces the observed trends in transport convergence, tropical Pacific SST, and SST gradient along the equator over the last half century. If the observed trends and those simulated in the MIROCH model are ultimately related to greenhouse gas forcing, these results suggest that the Bjerknes feedback, by affecting pycnocline transport convergences, may enhance warming that arises from anthropogenic forcing in the eastern tropical Pacific.  相似文献   

3≈6 Months Variation of Sea Surface Height in the South China Sea and Its Adjacent Ocean     

Jianyu Hu  Hiroshi Kawamura  Huasheng Hong  Fumiaki Kobashi  Dongxiao Wang 《Journal of Oceanography》2001,57(1):69-78

Sea surface height (SSH) variations with a period of 36 months (SSH36 variations) in the South China Sea (SCS) and its adjacent ocean are intensively investigated using six years of TOPEX/POSEIDON-derived SSH data. The results show that there appears higher energy of SSH36 variations in the east of the Luzon Strait and in some areas of the SCS, both of which are correlated with each other. The SSH36 variations usually propagate westward in the subtropical region of the northern Pacific Ocean and turn northward in the east of the Luzon Strait while they sometimes propagate into the SCS through the Luzon Strait with the phase speed of about 11–12 cm/s, which may be considered as Rossby waves. It can be inferred that the SSH36 variations are strongly associated with current structures and eddies in the SCS because of their significant intensiveness. The SSH variations with the period of 6 months are more dominant than those with the other periods in the SCS.  相似文献   

南海表层水温甚低频振荡的动力学机制     

傅刚  周发琇  于慎余  王东晓 《中国海洋大学学报(自然科学版)》1994,(4)

用一个简单的海洋模式，研究了东亚季风异常对南海表层水温（ＳＳＴ）的影响，发现南海表层水温的甚低频振荡是东亚季风异常风应力强迫所致．这种甚低频振荡主要反映在深水区，其空间分布呈椭圆形，几乎与南海海盆形状一致。从海盆中央到边缘振幅逐渐减少，ＳＳＴ的甚低频振荡是非行进波，无明显传播特征。  相似文献   

On the features of the SST annual cycle and surface heat budget in the South China Sea   总被引：1，自引：1，他引：1  

Wang Dongxiao  Zhou Faxiu  Li Yongping 《海洋学报(英文版)》1996,15(1):111-125

The annual cycle in the ocean and atmosPhere system 15 the important signal of the climatic variabilities.Observed studies had indicated that the seasonal feature of the climatic system which 15 of an annual period 15 due to the seasonal variation of the solar radiation.Funher researches has shown that the formation and maintenance of the annual cycle of the thermal condition(situation)in the upper oceans are the results of both dynamical and thermal processes which both are involved in air-sea interaction.Since researches on the large-scale air-sea interaction were Propoed,sea surface temperature(SST)has always been the primary object to observe,study and predict by the scientists.  相似文献   

South China Sea Monsoon Experiment （SCSMEX） and the East Asian Monsoon   总被引：3，自引：0，他引：3       下载免费PDF全文

DING Yihui  LI Chongyin  HE Jinhai  CHEN Longxun  GAN Zijun  QIAN Yongfu  YAN Junyue  WANG Dongxiao  SHI Ping  FANG Wendong  XU Jianping  LI Li 《Acta Meteorologica Sinica》2006,20(2):159-190

The SCSMEX is a joint atmospheric and oceanic experiment by international efforts, aiming at studying the onset, maintenance, and variability of the South China Sea (SCS) summer monsoon, thus improving the monsoon prediction in Southeast and East Asian regions. The field experiment carried out in May-August 1998 was fully successful, with a large amount of meteorological and oceanographic data acquired that have been used in four dimensional data assimilations by several countries, in order to improve their numerical simulations and prediction. These datasets are also widely used in the follow-up SCS and East Asian monsoon study. The present paper has summarized the main research results obtained by Chinese meteorologists which cover six aspects: (1) onset processes and mechanism of the SCS summer monsoon; (2) development of convection and mesoscale convective systems (MCSs) during the onset phase and their interaction with large-scale circulation; (3) low-frequency oscillation and teleconnection effect; (4) measurements of surface fluxes over the SCS and their relationship with the monsoon activity; (5) oceanic thermodynamic structures, circulation, and mesoscale eddies in the SCS during the summer monsoon and their relationship with ENSO events; and (6) numerical simulations of the SCS and East Asian monsoon.  相似文献   

南海夏季风爆发前后海-气界面热交换特征   总被引：20，自引：1，他引：20  

蒋国荣  何金海  王东晓  张韧  阎俊岳  姚华栋 《气象学报》2004,62(2):189-199

文中利用 2 0 0 0与 2 0 0 2年二次南海海 气通量观测资料和同期西沙站资料 ,研究了南海夏季风爆发前后海洋表面热收支变化特征。研究表明 :南海夏季风爆发前后 ,影响海面热收支变化的主要分量是净短波辐射通量和潜热通量 ,在季风爆发前后不同阶段 ,二个分量的变化有不同表现形式 ,但不论二者如何变化 ,季风爆发与活跃期 ,海面热收入减小或为净支出 ;季风爆发前及中断期间 ,海面热收入逐渐增加 ;由于大的热惯性 ,海温变化落后于海面热收支的变化 ,海温的这种滞后效应通过影响潜热通量调节海面热收支的变化 ,又反过来影响自身的变化 ,形成短期振荡过程 ,这种振荡过程与季风的活跃、中断过程相对应。  相似文献