共查询到20条相似文献，搜索用时 32 毫秒
1.
The effect of mesoscale eddy variability on the Japan/East Sea mean circulation is examined from satellite altimeter data
and results from the Naval Research Laboratory Layered Ocean Model (NLOM). Sea surface height variations from the Geosat-Exact
Repeat Mission and TOPEX/POSEIDON altimeter satellites imply geostrophic velocities. At the satellite crossover points, the
total velocity and the Reynolds stress due to geostrophic mesoscale turbulence are calculated. After spatial interpolation
the momentum flux and effect on geostrophic balance indicates that the eddy variability aids in the transport of the Polar
Front and the separation of the East Korean Warm Current (EKWC). The NLOM results elucidate the impact of eddy variability
on the EKWC separation from the Korean coast. Eddy variability is suppressed by either increasing the model viscosity or decreasing
the model resolution. The simulations with decreased eddy variability indicate a northward overshoot of the EKWC. Only the
model simulation with sufficient eddy variability depicts the EKWC separating from the Korean coast at the observed latitude.
The NLOM simulations indicate mesoscale influence through upper ocean-topographic coupling.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
Comparison of surface current variations observed by TOPEX altimeter with TOLEX-ADCP data 总被引：1，自引：0，他引：1
Variations of surface current velocity derived by the TOPEX altimeter are compared with data from Tokyo-Ogasawara Line Experiment (TOLEX)-Acoustic Doppler Current Profiler (ADCP) monitoring for a period from October 1992 to July 1993. Since the locations of ADCP ship track and TOPEX altimeter ground tracks do not coincide with each other, and the temporal and spatial sampling are also different between the ADCP and altimeter observations, re-sampling, interpolation and smoothing in time and space are needed to the ADCP and altimeter data. First, the interpolated TOPEX sea surface height is compared with sea level data at Chichijima in the Ogasawara Islands. It is found that aliasing caused by the tidal correction error for M2 constituent in the TOPEX data is significant. Therefore, comparison of the TOPEX data with the TOLEX-ADCP data is decided to be made by using cross-track velocity components of the surface current, which are considered to be relatively less affected by the errors in the tidal correction. The cross-track velocity variations derived from the TOPEX sea surface heights agree well with those of the ADCP observations. The altimeterderived velocity deviations associated with transition of the Kuroshio paths coincide with the ADCP data. It is quantitatively confirmed that the TOPEX altimeter is reliable to observe the synoptic variations of surface currents including fluctuations of the Kuroshio axis. 相似文献
3.
The Japan Sea is one of the eddy-rich areas in the world. Many researchers have described the variability of the eddy field and its structure in the Tsushima Warm Current region. On the other hand, since there are few data covering the northern part of the Japan Sea, we are not able to understand the detailed variability of the eddy field there. The variation of the eddy field in the Japan Sea is investigated using the temporal fluctuations of sea surface height measured by altimetric data from TOPEX/POSEIDON and ERS-2. Tidal signals are eliminated from the altimetric data on the basis of the results of Morimoto et al. (2000). Distributions of sea surface dynamic height are produced by using the optimal interpolation method every month. The distributions warm and cold eddies that we obtained coincide well with the observed isotherms at 100 m depth measured by the Japan Sea National Fisheries Research Institute and the sea surface temperature measured by satellite. There are areas with high RMS variability of temporal fluctuation of sea surface dynamic height in the Yamato Basin, the Ulleung Basin, east of North Korea, the eastern part of the Yamato Rise, the Tsushima Strait and west of Hokkaido. The characteristics of eddy propagation in the high RMS variability regions are examined using a lag correlation analysis. Seasonal variations in the number of warm and cold eddies are also examined. 相似文献
4.
We present an improved crossover adjustment procedure to determine mean sea surface height using TOPEX, 35-day repeat phase ERS-1, Geosat, and 168-day repeat phase ERS-1 satellite altimeter data. The mean sea surface frame defined by the TOPEX data is imposed as certain constraints in our crossover adjustment procedure rather than held fixed as in some other procedures. The new procedure is discussed in detail. Equations are developed to incorporate the a priori information of Topex data as well as other satellite altimeter data. The numerical computation result shows that the rms crossover discrepancies are reduced by an order of 1 cm when the Topex data is not fixed. Furthermore, the computed mean sea surface is less noisy and more realistic than that computed by the traditional procedure. 相似文献
5.
P. THIBAUT L. AMAROUCHE O. Z. ZANIFE N. STEUNOU P. VINCENT P. RAIZONVILLE 《Marine Geodesy》2013,36(3-4):409-431
Poseidon-2 is the dual frequency radar altimeter embarked on the CNES/NASA oceanographic satellite Jason-1 that was launched on 7 December 2001. The primary objective of the Jason-1 mission is to continue the high accuracy time series of altimeter measurements that began with TOPEX in 1992. To achieve this goal, it is necessary to improve each component of the ground processing continually. Among these components are the look-up correction tables that are used to correct the estimations (range, significant waveheight, and sigma naught) issued from the retracking algorithms (on-board and ground). Look-up tables were first computed taking into account the prelaunch characteristics of the altimeter. They have to be updated to take into account better all the in-flight characteristics of the altimeter and all the updated ground algorithms that can impact the estimation process. The aim of this article is to describe the radar altimeter simulator of performances that has been used to compute look-up tables, to display the freshly computed look-up tables, and to discuss the consequences of these new corrections on the products provided to the users. The updated look-up correction tables allow improvement of SWH estimation, in particular with respect to TOPEX SWH data. It is also shown that no range dependency on SWH has to be looked for in these tables, and that the on-board TOPEX and Poseidon-2 tracking systems may contain the differences explaining the relative sea state bias between both altimeters. 相似文献
6.
Jason-1 Altimeter Ground Processing Look-Up Correction Tables 总被引：1，自引：0，他引：1
P. Thibaut L. Amarouche O. Z. Zanife N. Steunou P. Vincent P. Raizonville 《Marine Geodesy》2004,27(3):409-431
Poseidon-2 is the dual frequency radar altimeter embarked on the CNES/NASA oceanographic satellite Jason-1 that was launched on 7 December 2001. The primary objective of the Jason-1 mission is to continue the high accuracy time series of altimeter measurements that began with TOPEX in 1992. To achieve this goal, it is necessary to improve each component of the ground processing continually. Among these components are the look-up correction tables that are used to correct the estimations (range, significant waveheight, and sigma naught) issued from the retracking algorithms (on-board and ground). Look-up tables were first computed taking into account the prelaunch characteristics of the altimeter. They have to be updated to take into account better all the in-flight characteristics of the altimeter and all the updated ground algorithms that can impact the estimation process. The aim of this article is to describe the radar altimeter simulator of performances that has been used to compute look-up tables, to display the freshly computed look-up tables, and to discuss the consequences of these new corrections on the products provided to the users. The updated look-up correction tables allow improvement of SWH estimation, in particular with respect to TOPEX SWH data. It is also shown that no range dependency on SWH has to be looked for in these tables, and that the on-board TOPEX and Poseidon-2 tracking systems may contain the differences explaining the relative sea state bias between both altimeters. 相似文献
7.
Planetary waves are key to large-scale dynamical adjustment in the global ocean as they transfer energy from the east to the west side of oceanic basins; they connect the forcing in the ocean interior with the variability at its boundaries; and they change the local heat content, thus coupling oceanic, atmospheric, and biological processes. Planetary waves, mostly of the first baroclinic mode, are observed as distinctive patterns in global time series of sea surface height anomaly (SSHA) and heat storage. The goal of this study is to compare and validate large-scale SSHA signals from coupled ocean-atmosphere general circulation Model for Interdisciplinary Research on Climate (MIROC) with TOPEX/POSEIDON satellite altimeter observations. The last decade of the models’ time series is selected for comparison with the altimeter data. The wave patterns are separated from the meso- and large-scale SSHA signals by digital filters calibrated to select the same spectral bands in both model and altimeter data. The band-wise comparison allows for an assessment of the model skill to simulate the dynamical components of the observed wave field. Comparisons regarding both the seasonal cycle and the Rossby wave field differ significantly among basins. When carried within the same basin, differences can occur between equal latitudes in opposite hemispheres. Furthermore, at some latitudes the MIROC reproduces biannual, annual and semiannual planetary waves with phase speeds and average amplitudes similar to those observed by the altimeter, but with significant differences in phase. 相似文献
8.
南海TOPEX海面高度资料的混合同化试验 总被引：16，自引：10，他引：16
应用普林斯顿海洋模式（POM），对冬季南海由TOPEX／Poseidon得到的卫星遥感海面高度资料进行混合（blending)同化试验。混合同化的权重系数由以下两者决定：南海POM模式对冬季风强迫产生响应的海面高度场之标准方差；对应期间ＴＯＰＥＸ海面高度资料的标准方差。同化结果表明，混合同化方法不失为一种简单而又有效的同化方案。同化得到的南海环流结构与未同化的模式响应场比较可以发现：海面高度资料的同化试验能够有效地修正南海环流的若干大尺度特征，特别是对冬季黑潮入侵南海东北部的动力过程，同化结果有了更准确的描述。同时，另一个重要的修正表现在：同化试验中瞬变的中等尺度涡旋得到加强，体现了南海海洋天气尺度涡被资料同化所“唤醒”（trigger)。这种“唤醒”不仅明显地反映在表层环流场中，对南海次表层动力、热盐结构也有一定的影响。 相似文献
9.
Calibration/Validation of an Altimeter Wave Period Model and Application to TOPEX/Poseidon and Jason-1 Altimeters 总被引：1，自引：0，他引：1
The altimeter radar backscatter cross-section is known to be related to the ocean surface wave mean square slope statistics, linked to the mean surface acceleration variance according to the surface wave dispersion relationship. Since altimeter measurements also provide significant wave height estimates, the precedent reasoning was used to derive empirical altimeter wave period models by combining both significant wave height and radar backscatter cross-section measurements. This article follows such attempts to propose new algorithms to derive an altimeter mean wave period parameter using neural networks method. Two versions depending on the required inputs are presented. The first one makes use of Ku-band measurements only as done in previous studies, and the second one exploits the dual-frequency capability of modern altimeters to better account for local environmental conditions. Comparison with in situ measurements show high correlations which give confidence in the derived altimeter wave period parameter. It is further shown that improved mean wave characteristics can be obtained at global and local scales by using an objective interpolation scheme to handle relatively coarse altimeter sampling and that TOPEX/Poseidon and Jason-1 altimeters can be merged to provide altimeter mean wave period fields with a better resolution. Finally, altimeter mean wave period estimates are compared with the WaveWatch-III numerical wave model to illustrate their usefulness for wave models tuning and validation. 相似文献
10.
The altimeter radar backscatter cross-section is known to be related to the ocean surface wave mean square slope statistics, linked to the mean surface acceleration variance according to the surface wave dispersion relationship. Since altimeter measurements also provide significant wave height estimates, the precedent reasoning was used to derive empirical altimeter wave period models by combining both significant wave height and radar backscatter cross-section measurements. This article follows such attempts to propose new algorithms to derive an altimeter mean wave period parameter using neural networks method. Two versions depending on the required inputs are presented. The first one makes use of Ku-band measurements only as done in previous studies, and the second one exploits the dual-frequency capability of modern altimeters to better account for local environmental conditions. Comparison with in situ measurements show high correlations which give confidence in the derived altimeter wave period parameter. It is further shown that improved mean wave characteristics can be obtained at global and local scales by using an objective interpolation scheme to handle relatively coarse altimeter sampling and that TOPEX/Poseidon and Jason-1 altimeters can be merged to provide altimeter mean wave period fields with a better resolution. Finally, altimeter mean wave period estimates are compared with the WaveWatch-III numerical wave model to illustrate their usefulness for wave models tuning and validation. 相似文献
11.
TOPEX altimeter data of 1993 have been analyzed to study the following three types of oceanographic phenomena in the Indian Ocean: (1) sea level variability of the Indian Ocean (20=S to 25=N. 40=E to 100=E): (2) sea surface height signals of the Somali eddy; and (3) sea surface slope variations of the equatorial Indian Ocean (EIO) spanning 5=S to 5=N and 45=E to 95=E. Root‐mean‐square sea level variability revealed the presence of Rossby waves in the southern Indian Ocean. Fast Fourier technique analysis of a few passes near the Somali region is used to study the formation and dissipation of an anticyclonic eddy. 相似文献
12.
Tidal Correction of Altimetric Data in the Japan Sea 总被引：2，自引：0，他引：2
Satellite altimetric data have been very useful in the study of variation in the eddy field of the ocean. In order to investigate the variation in the eddy field, we have to remove tidal signals from altimetric data. However, global tidal models do not have sufficient accuracy in marginal seas such as the Japan Sea. In this study, we carried out harmonic analysis of temporal fluctuations of sea surface height data in the Japan Sea measured by TOPEX/POSEIDON. We could eliminate the tidal signals from altimetric data of TOPEX/POSEIDON and also from ERS-2 altimetric data with use of the harmonic constants derived from TOPEX/POSEIDON and tide gauge data along the coast. We draw co-tidal and co-range charts in the Japan Sea using the result of the harmonic analysis of TOPEX/POSEIDON altimetric data and tide gauge data along the coast. The results obtained turn out to be very useful for the tidal correction of altimetric data from satellite in the Japan Sea. 相似文献
13.
I. R. Young 《Ocean Engineering》1999,26(1):67
Mean monthly values of altimeter wind speed and wave height are compared with data from NDBC buoys. As a result of these comparisons, corrections are made to the raw data products available from these satellites. Data from the GEOSAT, TOPEX and ERS1 missions corrected in this fashion are used to show that there have been no measurable changes in the global wind and wave climate during the 10 years spanned by these various missions. It is proposed that the corrected values of wind speed and wave height provide the basis for the formation of a long-term global data base which spans the periods of these multiple missions. 相似文献
14.
We present an improved crossover adjustment procedure to determine mean sea surface height using TOPEX, 35-day repeat phase ERS-1, Geosat, and 168-day repeat phase ERS-1 satellite altimeter data. The mean sea surface frame defined by the TOPEX data is imposed as certain constraints in our crossover adjustment procedure rather than held fixed as in some other procedures. The new procedure is discussed in detail. Equations are developed to incorporate the a priori information of Topex data as well as other satellite altimeter data. The numerical computation result shows that the rms crossover discrepancies are reduced by an order of 1 cm when the Topex data is not fixed. Furthermore, the computed mean sea surface is less noisy and more realistic than that computed by the traditional procedure. 相似文献
15.
Trajectories of mesoscale eddies in the Kuroshio recirculation region were investigated by using sea surface height (SSH)
anomaly observed by the TOPEX/POSEIDON and ERS altimeters. Cyclonic and anticyclonic eddies have been traced on maps of the
filtered SSH anomaly fields composed from the altimeter observations every ten days. Both the cyclonic and anticyclonic eddies
propagate westward in the Kuroshio recirculation region from a region south of the Kuroshio Extension. The propagation speed
of these eddies has been estimated as about 7 cm s−1, which is much faster than the phase speed theoretically estimated for the baroclinic first-mode Rossby wave in the study
area. It was also found that in the Izu-Ogasawara Ridge region, most of eddies pass through the gap between the Hachijojima
Island and Ogasawara (Bonin) Islands, and some of the eddies decay around the Izu-Ogasawara Ridge. It seems that the trajectory
of the eddies is crucially affected by the bottom topography. In the region south of Shikoku and east of Kyushu, some of the
eddies coalesce with the Kuroshio. It is also suggested that this coalescence may trigger the path variation of the Kuroshio
in the sea south of Japan.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
南海中尺度涡旋对热带气旋的响应：个例研究 总被引：4，自引：0，他引：4
利用TOPEX／POsEIDON和Jason—1卫星高度计，SeaWiFS水色传感器和TMI微波成像仪等卫星遥感资料研究了南海中尺度涡旋对热带气旋“玲玲”（Lingling，0123）、“灿都”（Chanthu，0405）和“榴莲”（Durian，0621）的响应，得到以下研究结果：（1）位于热带气旋“玲玲”和“榴莲”移动路径右侧的冷涡在热带气旋经过后增强，表现在海面高度距平和海表温度的较大幅度下降，以及叶绿素a的爆发性升高；（2）位于“玲玲”移动路径左侧以及“灿都”路径上的暖涡在热带气旋经过后减弱，表现在海面高度距平和海表温度的下降，而叶绿素a变化不太明显；（3）当热带气旋“玲玲”和“灿都”经过暖涡时，热带气旋的强度迅速增大，这表明暖涡可能有助于热带气旋的加强． 相似文献
17.
PIERRE QUEFFEULOU 《Marine Geodesy》2013,36(3-4):495-510
Since July 1991, six altimeter missions have been launched successfully, and they have provided almost continuous wave height measurements for more than 12 years. Long-term series of wave height measurements are of major interest for climatology and oceanic wave modeling. Before using such data, the measurements have to be validated, and the homogeneity of the data from various satellites has to be checked. Significant wave height measurements from ERS, TOPEX/Poseidon, GEOSAT Follow-on, Jason-1 and ENVISAT altimeters are validated using cross-altimeter and buoy comparisons. Emphasis is put on the two recent missions Jason-1 and ENVISAT. Corrections for biases and trends are proposed for the six altimeters, allowing the generation of consistent and homogeneous data. Tests of these corrections are performed over global ocean simple statistics. 相似文献
18.
Long-Term Validation of Wave Height Measurements from Altimeters 总被引：1，自引：0，他引：1
Pierre Queffeulou 《Marine Geodesy》2004,27(3):495-510
Since July 1991, six altimeter missions have been launched successfully, and they have provided almost continuous wave height measurements for more than 12 years. Long-term series of wave height measurements are of major interest for climatology and oceanic wave modeling. Before using such data, the measurements have to be validated, and the homogeneity of the data from various satellites has to be checked. Significant wave height measurements from ERS, TOPEX/Poseidon, GEOSAT Follow-on, Jason-1 and ENVISAT altimeters are validated using cross-altimeter and buoy comparisons. Emphasis is put on the two recent missions Jason-1 and ENVISAT. Corrections for biases and trends are proposed for the six altimeters, allowing the generation of consistent and homogeneous data. Tests of these corrections are performed over global ocean simple statistics. 相似文献
19.
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
20.
Robert E. Cheney Bruce C. Douglas David T. Sandwell James G. Marsh Thomas V. Martin John J. McCarthy 《Marine Geophysical Researches》1984,7(1-2):17-32
Satellite-borne altimeters have had a profound impact on geodesy, geophysics, and physical oceanography. To first order approximation,
profiles of sea surface height are equivalent to the geoid and are highly correlated with seafloor topography for wavelengths
less than 1000 km. Using all available Geos-3 and Seasat altimeter data, mean sea surfaces and geoid gradient maps have been
computed for the Bering Sea and the South Pacific. When enhanced using hill-shading techniques, these images reveal in graphic
detail the surface expression of seamounts, ridges, trenches, and fracture zones. Such maps are invaluable in oceanic regions
where bathymetric data are sparse. Superimposed on the static geoid topography is dynamic topography due to ocean circulation.
Temporal variability of dynamic height due to oceanic eddies can be determined from time series of repeated altimeter profiles.
Maps of sea height variability and eddy kinetic energy derived from Geos-3 and Seasat altimetry in some cases represent improvements
over those derived from standard oceanographic observations. Measurement of absolute dynamic height imposes stringent requirements
on geoid and orbit accuracies, although existing models and data have been used to derive surprisingly realistic global circulation
solutions. Further improvement will only be made when advances are made in geoid modeling and precision orbit determination.
In contrast, it appears that use of altimeter data to correct satellite orbits will enable observation of basin-scale sea
level variations of the type associated with climatic phenomena. 相似文献