共查询到20条相似文献，搜索用时 31 毫秒
1.
Since 1996, global, near-real-time maps of mesoscale anomalies derived from tandem sampling provided by altimeters aboard the TOPEX/Poseidon and ERS-2 satellites have been posted on web pages hosted at the Colorado Center for Astrodynamics Research. The original, near-real-time processing system was based on a quick-look analysis that referenced the data to a high-resolution gridded mean sea surface available at the time. Recently, state-of-the-art mean sea surfaces have been derived that are based on a more complete record of altimeter observations. An updated mesoscale monitoring system based on a new mean surface is described and shown to provide improved mesoscale monitoring to the successful system implemented in 1996. 相似文献
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Qi Shu Fangli Qiao Jiping Liu Zhenya Song Zhiqiang Chen Jiechen Zhao Xunqiang Yin Yajuan Song 《海洋学报(英文版)》2021,40(10):65-75
To improve the Arctic sea ice forecast skill of the First Institute of Oceanography-Earth System Model (FIO-ESM) climate forecast system, satellite-derived sea ice concentration and sea ice thickness from the Pan-Arctic Ice-Ocean Modeling and Assimilation System (PIOMAS) are assimilated into this system, using the method of localized error subspace transform ensemble Kalman ?lter (LESTKF). Five-year (2014–2018) Arctic sea ice assimilation experiments and a 2-month near-real-time forecast in August 2018 were conducted to study the roles of ice data assimilation. Assimilation experiment results show that ice concentration assimilation can help to get better modeled ice concentration and ice extent. All the biases of ice concentration, ice cover, ice volume, and ice thickness can be reduced dramatically through ice concentration and thickness assimilation. The near-real-time forecast results indicate that ice data assimilation can improve the forecast skill significantly in the FIO-ESM climate forecast system. The forecasted Arctic integrated ice edge error is reduced by around 1/3 by sea ice data assimilation. Compared with the six near-real-time Arctic sea ice forecast results from the subseasonal-to-seasonal (S2S) Prediction Project, FIO-ESM climate forecast system with LESTKF ice data assimilation has relatively high Arctic sea ice forecast skill in 2018 summer sea ice forecast. Since sea ice thickness in the PIOMAS is updated in time, it is a good choice for data assimilation to improve sea ice prediction skills in the near-real-time Arctic sea ice seasonal prediction. 相似文献
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Kuh Kim Yun Bae Kim Jong Jin Park SungHyun Nam Kyung-Ae Park Kyung-Il Chang 《Ocean Science Journal》2005,40(1):25-44
Long-term, continuous, and real-time ocean monitoring has been undertaken in order to evaluate various oceanographic phenomena
and processes in the East/Japan Sea. Recent technical advances combined with our concerted efforts have allowed us to establish
a real-time monitoring system and to accumulate considerable knowledge on what has been taking place in water properties,
current systems, and circulation in the East Sea. We have obtained information on volume transport across the Korea Strait
through cable voltage measurements and continuous temperature and salinity profile data from ARGO floats placed throughout
entire East Sea since 1997. These ARGO float data have been utilized to estimate deep current, inertial kinetic energy, and
changes in water mass, especially in the northern East Sea. We have also developed the East Sea Real-time Ocean Buoy (ESROB)
in coastal regions and made continual improvements till it has evolved into the most up-to-date and effective monitoring system
as a result of remarkable technical progress in data communication systems. Atmospheric and oceanic measurements by ESROB
have contributed to the recognition of coastal wind variability, current fluctuations, and internal waves near and off the
eastern coast of Korea. Long-term current meter moorings have been in operation since 1996 between Ulleungdo and Dokdo to
monitor the interbasin deep water exchanges between the Japanese and Ulleung Basins. In addition, remotely sensed satellite
data could facilitate the investigation of atmospheric and oceanic surface conditions such as sea surface temperature (SST),
sea surface height, near-surface winds, oceanic color, surface roughness, and so on. These satellite data revealed surface
frontal structures with a fairly good spatial resolution, seasonal cycle of SST, atmospheric wind forcing, geostrophic current
anomalies, and biogeochemical processes associated with physical forcing and processes. Since the East Sea has been recognized
as a natural laboratory for global oceanic changes and a clue to abrupt climate change, we aim at constructing a 4-D continuous
real-time monitoring system, over a decade at least, using the most advanced techniques to understand a variety of oceanic
processes in the East Sea. 相似文献
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海洋中尺度涡在本质上是属于满足准地转平衡的大尺度运动,因此理论上,其在短时间内的运动将主要受到准地转平衡关系的约束,而外部强迫场的影响在短期内不会明显改变其运动特征。基于上述思想,我们提出了一种基于四维变分同化初始场的中尺度涡旋预报方案。为了检验该方案的可行性,本文使用区域海洋模式(regional ocean modeling system, ROMS)和其内建的增量强约束四维变分同化(incremental strong constraint four dimensional variational, I4D-Var)模块,建立了一个南海海洋同化模拟系统。首先,通过I4D-Var方法将AVISO卫星高度计资料同化到海洋数值模拟中,获得了理想的中尺度涡同化模拟结果。同化、模式模拟和观测三者的中尺度涡统计结果表明,该同化系统模拟的南海中尺度涡的路径、半径、海表高度异常和振幅等特征信息与AVISO(Archiving ValidationandInterpolationofSatelliteOceanographicData)观测结果高度吻合,同时在深度上的分析表明,涡旋对应的温度、盐度和密度均得到有效的调整。然后,将该同化系统的模拟结果做为初始场,对某一特定时段的南海中尺度涡进行了后报模拟和结果的定量化分析。通过比较后报模拟与观测资料中对应涡旋的海表面高度异常(sea surface height anomalies, SSHA)相关系数、涡心差距和半径绝对误差,证明该方案的中尺度涡后报时效至少可达10 d以上。后报实验结果验证了该中尺度涡预报方案的可行性,从而为中尺度涡的预报提供一定的理论基础和可行性方案。 相似文献
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Oceanic geostrophic turbulence theory predicts significant inverse kinetic energy(KE) cascades at scales larger than the energy injection wavelength. However, the characteristics of the mesoscale variabilities associated with the inverse KE cascade in the real oceans have not been clear enough up to now. To further examine this problem,we analyzed the spectral characteristics of the oceanic mesoscale motions over the scales of inverse KE cascades based on high-resolution gridded altimeter data. The applicability of the quasigeostrophic(QG) turbulence theory and the surface quasigeostrophic(SQG) turbulence theory in real oceans is further explored. The results show that the sea surface height(SSH) spectral slope is linearly related to the eddy-kinetic-energy(EKE) level with a high correlation coefficient value of 0.67. The findings also suggest that the QG turbulence theory is an appropriate dynamic framework at the edge of high-EKE regions and that the SQG theory is more suitable in tropical regions and low-EKE regions at mid-high latitudes. New anisotropic characteristics of the inverse KE cascade are also provided. These results indicate that the along-track spectrum used by previous studies cannot reveal the dynamics of the mesoscale variabilities well. 相似文献
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This study concerns the determination of a regional geoid model in the North Atlantic area surrounding the Azores islands by combining multi-mission altimetry from the ERS (European Remote Sensing) satellites and surface gravity data. A high resolution mean sea surface, named AZOMSS99, has been derived using altimeter data from ERS-1 and ERS-2 35-day cycles, spanning a period of about four years, and from ERS-1 geodetic mission. Special attention has been paid to data processing of points around the islands due to land contamination on some of the geophysical corrections. A gravimetric geoid has been computed from all available surface gravity, including land and sea observations acquired during an observation campaign that took place in the Azores in October 1997 in the scope of a European and a Portuguese project. Free air gravity anomalies were derived by altimetric inversion of the mean sea surface heights. These were used to fill the large gaps in the surface gravity and combined solutions were computed using both types of data. The gravimetric and combined solutions have been compared with the mean sea surface and GPS (Global Positioning System)-levelling derived geoid undulations in five islands. It is shown that the inclusion of altimeter data improves geoid accuracy by about one order of magnitude. Combined geoid solutions have been obtained with an accuracy of better than one decimetre. 相似文献
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This study concerns the determination of a regional geoid model in the North Atlantic area surrounding the Azores islands by combining multi-mission altimetry from the ERS (European Remote Sensing) satellites and surface gravity data. A high resolution mean sea surface, named AZOMSS99, has been derived using altimeter data from ERS-1 and ERS-2 35-day cycles, spanning a period of about four years, and from ERS-1 geodetic mission. Special attention has been paid to data processing of points around the islands due to land contamination on some of the geophysical corrections. A gravimetric geoid has been computed from all available surface gravity, including land and sea observations acquired during an observation campaign that took place in the Azores in October 1997 in the scope of a European and a Portuguese project. Free air gravity anomalies were derived by altimetric inversion of the mean sea surface heights. These were used to fill the large gaps in the surface gravity and combined solutions were computed using both types of data. The gravimetric and combined solutions have been compared with the mean sea surface and GPS (Global Positioning System)-levelling derived geoid undulations in five islands. It is shown that the inclusion of altimeter data improves geoid accuracy by about one order of magnitude. Combined geoid solutions have been obtained with an accuracy of better than one decimetre. 相似文献
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Ocean temperature changes between 1991 and 2005 in the eastern Tasman Sea were analysed. This area was chosen because of a combination of data availability, low mesoscale variability and because of its importance in determining the climate of the downwind New Zealand landmass. A large warming extending to the full depth of the water column (c. 800 m) was found to have occurred between 1996 and 2002. This warming was seen in measurements by expendable bathythermographs and also in satellite sea surface temperature and sea surface height products, and has a clear impact on New Zealand's terrestrial temperature. The nature of the warming is discussed, together with likely forcing mechanisms. No local forcing mechanisms are consistent with the observed warming, leading to the conclusion that the signal seen in the Tasman Sea is part of a larger South Pacific‐wide phenomenon. 相似文献
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吕宋海峡两侧中尺度涡统计 总被引：4，自引：0，他引：4
利用1993-2000年间的T/P卫星高度计轨道资料的时间序列和MODAS同化产品中的卫星高度计最优插值资料对南海东北部海区中尺度涡旋进行动态追踪。按照给定的标准从2种资料中提取了涡旋信息并对其特征量进行统计分析。结果表明,南海东北部海区中尺度涡旋十分活跃,平均每年6个,其中暖涡4个,尺度一般为200~250 km,平均地转流速为44 cm/s;冷涡每年平均2个,尺度一般为150~200 km,平均地转流速为-37 cm/s。吕宋海峡两侧涡旋的比较分析表明,南海东北部海区仍属于西北太平洋副热带海区的涡旋带,冷、暖涡旋处于不断的形成—西移—消散过程中。南海东北部中尺度冷涡大多是南海内部产生的,而暖涡与吕宋海峡外侧暖涡有一定的联系又具有相对的独立性。分析认为西北太平洋的西行暖涡在到达吕宋海峡时,受到黑潮东翼东向下倾的等密度面的抑制和岛链的阻碍,涡旋停滞于吕宋海峡外侧并逐渐消弱,被阻挡于吕宋海峡东侧涡旋释放的能量,形成一支横穿吕宋海峡(同时横穿过黑潮)的高速急流,把能量传递给吕宋海峡西侧的涡旋,使其得到强化,这是吕宋海峡两侧涡旋联系的一种重要机制。 相似文献
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为了从理论上解释中尺度涡旋冷暖性质与涡旋旋转方向的关系,本文基于中尺度涡的几何特征,做出如下假设：中尺度涡具有对称的几何形态,涡旋中海洋要素沿径向具有线性化变化的特征。从原始方程组出发,利用柱坐标系和上述假设条件,略去耗散力,推导出了中尺度涡的一些冷暖特征,论证气旋式中尺度涡对应冷涡和反气旋式中尺度涡对应暖涡的涡旋冷暖特征与部分涡旋的观测不符的现象。结果表明,中心对称的形式可以作为对中尺度涡的几何特征的一个理想的形态近似,在考虑上述假设条件的理想环境下,柱坐标系在研究中尺度涡的几何性质上具有一定的优势。 相似文献
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中尺度涡旋是海洋中典型的中尺度现象，是海洋中能量传递的运输者，中尺度涡识别与提取是物理海洋学研究的重要内容之一，而中尺度涡自动发现算法是最基础的用于寻找与分析中尺度涡的工具。中尺度涡旋探测工作的数据来源主要为卫星高度计数据融合出的SLA数据，该数据可以客观的描述海洋表层高度状态。中尺度涡表示为SLA闭合等值线所包围的局部等值区域，涡旋识别需要从SLA数据中提取出稳定的闭合等值线结构。针对基于SLA数据中的中尺度涡探测的特点，本文提出了一种新的基于聚类方法的中尺度涡自动识别算法，通过对SLA数据集的分割与筛选将中尺度涡区域与背景区域分离，后建立区域内联系并将其映射到SLA地图上来提取中尺度涡结构。本文算法解决了传统探测算法中参数设定的敏感性问题，不需要进行稳定性测试，算法适应性增强。算法中加入了涡旋筛选机制，保证了结果的涡旋结构的稳定性，提高了识别准确率。在此基础上，本文选取了西北太平洋及中国南海地区进行了中尺度涡探测实验，实验结果展示出了本文算法在较传统算法提高算法效率的同时，也保持着较高的算法稳定性，可以在稳定识别各个单涡结构的同时识别稳定的多涡结构。 相似文献
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Martin Ekman 《Marine Geodesy》1999,22(1):31-35
The mean sea surface topography in the Baltic Sea and adjacent waters is reliably known in the Nordic height system NH 60. Using this knowledge we estimate differences between NH 60, based on the Amsterdam zero point, and Russian, Polish, and German height systems along the southeastern coast of the Baltic Sea, based on the Kronstadt zero point. The differences agree within a few centimeters. We also make a simple study of the mean sea level difference between Kronstadt and Amsterdam (which is found to have been approximately 25 cm when sea level was still to be seen there). 相似文献
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Mesoscale eddies play an important role in modulating the ocean circulation. Many previous studies on the threedimensional structure of mesoscale eddies were mainly based on composite analysis, and there are few targeted observations for individual eddies. A cyclonic eddy surveyed during an oceanographic cruise in the Northwest Pacific Ocean is investigated in this study. The three-dimensional structure of this cyclonic eddy is revealed by observations and simulated by the four-dimensional variational data assimilation(4 DVAR) system combined with the Regional Ocean Modeling System. The observation and assimilation results together present the characteristics of the cyclonic eddy. The cold eddy has an obvious dual-core structure of temperature anomaly.One core is at 50–150 m and another is at 300–550 m, which both have the average temperature anomaly of approximately-3.5°C. The salinity anomaly core is between 250 m and 500 m, which is approximately-0.3. The horizontal velocity structure is axis-asymmetric and it is enhanced on the eastern side of the cold eddy. In the assimilation experiment, sea level anomaly, sea surface temperature, and in situ measurements are assimilated into the system, and the results of assimilation are close to the observations. Based on the high-resolution assimilation output results, the study also diagnoses the vertical velocity in the mesoscale eddy, which reaches the maximum of approximately 10 m/d. The larger vertical velocity is found to be distributed in the range of 0.5 to 1 time of the normalized radius of the eddy. The validation of the simulation result shows that the 4 DVAR method is effective to reconstruct the three-dimensional structure of mesoscale eddy and the research is an application to study the mesoscale eddy in the Northwest Pacific by combining observation and assimilation methods. 相似文献
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This study investigated the seasonal variation in the atmospheric response to oceanic mesoscale eddies in the North Pacific Subtropical Countercurrent (STCC) and its mechanism, based on satellite altimetric and reanalysis datasets. Although mesoscale eddy in the study area is more active in summer, the sea surface temperature (SST) anomaly associated with mesoscale eddies is more intense and dipolar in winter, which is largely due to the larger background SST gradient. Similarly, the impact of the oceanic eddy on sea surface wind speed and heat flux is strongest in winter, whereas its effect on precipitation rate is more significant in summer. The study revealed that the SST gradient in STCC could impact the atmosphere layer by up to 800 hPa (900 hPa) in boreal winter (summer) through the dominant vertical mixing mechanism. Moreover, the intensity of the SST gradient causes such seasonal variation in mesoscale air-sea coupling in the study region. In brief, a stronger (weaker) background SST gradient field in wintertime (summertime) leads to a larger (smaller) eddy-induced SST anomaly, thus differently impacting atmosphere instability and transitional kinetic energy flux over oceanic eddies, leading to seasonal variation in mesoscale air-sea coupling intensity. 相似文献
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An analytical solution for the local suspended sediment concentration profile in tidal sea region 总被引：1，自引：0，他引：1
Kyung Tae Jung Jae Youll Jin Hyoun-Woo Kang Ho Jin Lee 《Estuarine, Coastal and Shelf Science》2004,61(4):657-667
The time-averaged and oscillatory solutions of the one-dimensional vertical (1DV) advection–diffusion equation for the suspended sediment have been derived analytically in a tidal sea region of finite water depth. The basic equation assumes constant eddy diffusivity and settling velocity. No net flux condition is set at the sea surface, while a boundary condition with the erosion rate and depositional velocity is prescribed at the sea bottom. The time-averaged solution has been derived in a straightforward manner, while the advection–diffusion equation governing the oscillatory concentration has been first transformed to a simple diffusion equation and then solved using the Galerkin-eigenfunction method. The former is given in a closed form, while the latter is presented in a series solution.A set of calculations has been performed to examine the change in the vertical structure as well as magnitude of the concentration response function. A possible use of the solution to make an estimate of the erosion rate at the sea bottom based on the concentration information at the sea surface is discussed. 相似文献
19.
海洋表面流场是海洋科学研究中需要着重考虑的环境参数,近实时的海洋表面流场精细化测量对海洋学研究有着重要意义,但是目前大多数海洋表面流场观测技术难以同步实现大范围近实时的海洋表面流场观测。文中在简要对比各类海洋表面流场测量方法的基础上,重点介绍了基于水色遥感图像观测反演海洋表面流场的鲁棒光流算法,该算法在流场计算过程中,能很好地保留流场细节信息。为直观验证本文测量方法的可靠性,文中提供了海洋表面流场的分析实例,同时给出了美国国家航空航天局(NASA)提供的OSCAR流场数据,对文中算法的可靠性进行了验证。 相似文献
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A parameterization of subgridscale surface fluxes over the marginal sea ice zone which has been used earlier in several studies is modified and applied to a nonhydrostatic mesoscale model. The new scheme accounts for the form drag of ice floes and is combined with a so-called flux averaging method for the determination of surface fluxes over inhomogeneous terrain. Individual fluxes over ice and water are calculated as a function of the blending height. It is shown by comparison with observations that the drag coefficients calculated with the new parameterization agree well with data. The original scheme strongly overestimates the form drag effect. An improvement is mainly obtained by an inclusion of stratification and by use of a more adequate coefficient of resistance for individual ice floes. The mesoscale model is applied to off-ice flows over the polar marginal sea ice zone. The model results show that under certain meteorological conditions the form drag can have a strong influence on the near-surface wind velocity and on the turbulent fluxes of momentum. Four case studies are carried out. The maximum influence of form drag occurs in the case with strong unstable stratification and with wind oblique to the ice edge. Under these conditions the wind stress on sea ice is modified by at least 100% for ice concentrations less than 50% if form drag is taken into account. 相似文献