共查询到20条相似文献，搜索用时 15 毫秒
1.
A time series of velocity profile in the upper 150 m of the equatorial Atlantic was gathered at 23W in 2002 within the PIRATA program. It constitutes the first time series of near surface current measurements simultaneous with altimetric data in the equatorial Atlantic. The surface slope anomaly along the equator is computed from satellite altimetry, and, as a proxy for the pressure gradient along the equator, compared with the wind and near surface current data. In a first step, a time series of the surface slope anomaly along the equator in the Atlantic is computed from the 10-year-long TOPEX/Poseidon sea level anomalies. A sensitivity study establishes the robustness of the calculation. Apart from a 15 cm bias, the equatorial sea surface slope anomalies estimated either from TOPEX/Poseidon or from Jason over the 6-month overlap (Feb.-Aug. 2002) do not reveal drastic differences. We produce two sea surface slope anomaly composite time series for 2002 (one with T/P data, the other with Jason data during the commissioning phase) and compare them to the wind and velocity data at 23W. As expected, the near surface velocity and depth of the upper limit of the equatorial undercurrent (EUC) are extremely well correlated with the surface pressure gradient anomaly. 10-year-long time series of altimetry-derived zonal sea surface slope anomaly and ECMWF ERA40 wind stress are also well correlated. They exhibit similar spectral content and similar anomalous years. This is a first step towards a full analysis of the EUC dynamics using altimetry, PIRATA data (near surface current and subsurface thermohaline structure) and model. These initial comparisons reinforce the utility of Jason measurements for continuing the 10-year and highly accurate TOPEX/Poseidon time series for study of equatorial signals. 相似文献
2.
SARAH T. GILLE 《Marine Geodesy》2013,36(1-2):47-57
The Kolmogorov-Smirnov (K-S) test is used to compare probability density functions (PDFs) of geostrophic velocities measured by the TOPEX, Poseidon, and Jason altimeters. Velocity PDFs are computed in 2.5° by 2.5° boxes for regions equatorward of 60° latitude. Although velocities measured by the TOPEX and Jason altimeters can differ, on the basis of the K-S test the velocities are statistically equivalent during the ～200 day period when the satellites followed the same orbit. Full records from TOPEX, Poseidon, and Jason show less agreement, which can be attributed to temporal variability in ocean surface velocities and differing levels of measurement noise. 相似文献
3.
TOPEX/Poseidon and Jason Equatorial Sea Surface Slope Anomaly in the Atlantic in 2002: Comparison with Wind and Current Measurements at 23W 总被引：1，自引：1，他引：0
C. PROVOSt S. ARNAULt N. CHOUAIb A. KARTAVTSEFF L. BUNGE E. SULTAN 《Marine Geodesy》2013,36(1-2):31-45
A time series of velocity profile in the upper 150 m of the equatorial Atlantic was gathered at 23W in 2002 within the PIRATA program. It constitutes the first time series of near surface current measurements simultaneous with altimetric data in the equatorial Atlantic. The surface slope anomaly along the equator is computed from satellite altimetry, and, as a proxy for the pressure gradient along the equator, compared with the wind and near surface current data. In a first step, a time series of the surface slope anomaly along the equator in the Atlantic is computed from the 10-year-long TOPEX/Poseidon sea level anomalies. A sensitivity study establishes the robustness of the calculation. Apart from a 15 cm bias, the equatorial sea surface slope anomalies estimated either from TOPEX/Poseidon or from Jason over the 6-month overlap (Feb.–Aug. 2002) do not reveal drastic differences. We produce two sea surface slope anomaly composite time series for 2002 (one with T/P data, the other with Jason data during the commissioning phase) and compare them to the wind and velocity data at 23W. As expected, the near surface velocity and depth of the upper limit of the equatorial undercurrent (EUC) are extremely well correlated with the surface pressure gradient anomaly. 10-year-long time series of altimetry-derived zonal sea surface slope anomaly and ECMWF ERA40 wind stress are also well correlated. They exhibit similar spectral content and similar anomalous years. This is a first step towards a full analysis of the EUC dynamics using altimetry, PIRATA data (near surface current and subsurface thermohaline structure) and model. These initial comparisons reinforce the utility of Jason measurements for continuing the 10-year and highly accurate TOPEX/Poseidon time series for study of equatorial signals. 相似文献
4.
The Jason-1 verification phase has proven to be a unique and successful calibration experiment to quantify the agreement with its predecessor TOPEX/Poseidon. Although both missions have met prescribed error budgets, comparison of the mean and time-varying sea surface height profiles from near simultaneous observations derived from the missions' Geophysical Data Records exhibit significant basin scale differences. Several suspected sources causing this disagreement are identified and improved upon, including (a) replacement of TOPEX and Jason project POE with enhanced orbits computed at GSFC within a consistent ITRF2000 terrestrial reference frame, (b) application of waveform retracking corrections to TOPEX significant wave height and sea surface heights, (c) resultant improved efficacy of the TOPEX sea state bias estimation from the value added sea surface height, and (d) estimation of Jason-1 sea state bias employing dual TOPEX/Jason crossover and collinear sea surface height residuals unique to the validation mission. The resultant mean sea surface height comparison shows improved agreement at better than 60 percent level of variance reduction with a standard deviation less then 0.5 cm. 相似文献
5.
Sarah T. Gille 《Marine Geodesy》2004,27(1):47-57
The Kolmogorov-Smirnov (K-S) test is used to compare probability density functions (PDFs) of geostrophic velocities measured by the TOPEX, Poseidon, and Jason altimeters. Velocity PDFs are computed in 2.5° by 2.5° boxes for regions equatorward of 60° latitude. Although velocities measured by the TOPEX and Jason altimeters can differ, on the basis of the K-S test the velocities are statistically equivalent during the ∼200 day period when the satellites followed the same orbit. Full records from TOPEX, Poseidon, and Jason show less agreement, which can be attributed to temporal variability in ocean surface velocities and differing levels of measurement noise. 相似文献
6.
Guoqi Han 《Marine Geodesy》2004,27(3):577-595
Sea level observations from the tandem TOPEX/Poseidon (T/P) and Jason-1 altimetry missions (2002-2003) are used to study characteristics of sea level and surface currents over the Scotian Shelf and Slope off Nova Scotia. The consistency and error characteristics of T/P and Jason-1 measurements are examined not only in terms of sea level and cross-track current anomalies but also with respect to current anomalies at crossovers, kinematic properties associated with Gulf Stream warm core rings (WCR), and the shelf-edge current transport. Nominal absolute currents are constructed by adding the altimetric geostrophic current anomalies to an annual-mean model circulation field. The concurrent frontal analysis data are analyzed for occurrence of the WCRs and associated kinematic properties are derived from altimetric current anomalies. The comparison of the sea level and cross-track current anomalies from January to July 2002 shows overall good agreement between T/P and Jason, with correlation coefficients different from zero at the 5% significance level at essentially all locations for sea level and at most locations for currents. The cross-track geostrophic current anomalies from January to July 2002 and from September 2002 to December 2003 are further used to calculate the root-mean-square (rms) current magnitude, and the normalized relative vorticity associated with WCRs. The altimetric currents are consistent with each other and complementary to frontal analysis data in deriving the properties of the WCRs. The rms current magnitude is ∼55 cm/s and the normalized relative vorticity is ∼0.15. The model-altimetry combined absolute currents are used to estimate near-surface transport associated with the shelf-edge current, showing good correlation between T/P and Jason estimates and strong seasonal changes. The current anomalies derived from altimetry and moored measurements are significantly (at the 5% significance level) correlated and comparable in the rms magnitude. 相似文献
7.
GUOQI HAN 《Marine Geodesy》2013,36(3-4):577-595
Sea level observations from the tandem TOPEX/Poseidon (T/P) and Jason-1 altimetry missions (2002–2003) are used to study characteristics of sea level and surface currents over the Scotian Shelf and Slope off Nova Scotia. The consistency and error characteristics of T/P and Jason-1 measurements are examined not only in terms of sea level and cross-track current anomalies but also with respect to current anomalies at crossovers, kinematic properties associated with Gulf Stream warm core rings (WCR), and the shelf-edge current transport. Nominal absolute currents are constructed by adding the altimetric geostrophic current anomalies to an annual-mean model circulation field. The concurrent frontal analysis data are analyzed for occurrence of the WCRs and associated kinematic properties are derived from altimetric current anomalies. The comparison of the sea level and cross-track current anomalies from January to July 2002 shows overall good agreement between T/P and Jason, with correlation coefficients different from zero at the 5% significance level at essentially all locations for sea level and at most locations for currents. The cross-track geostrophic current anomalies from January to July 2002 and from September 2002 to December 2003 are further used to calculate the root-mean-square (rms) current magnitude, and the normalized relative vorticity associated with WCRs. The altimetric currents are consistent with each other and complementary to frontal analysis data in deriving the properties of the WCRs. The rms current magnitude is ～55 cm/s and the normalized relative vorticity is ～0.15. The model-altimetry combined absolute currents are used to estimate near-surface transport associated with the shelf-edge current, showing good correlation between T/P and Jason estimates and strong seasonal changes. The current anomalies derived from altimetry and moored measurements are significantly (at the 5% significance level) correlated and comparable in the rms magnitude. 相似文献
8.
The Jason-1 verification phase has proven to be a unique and successful calibration experiment to quantify the agreement with its predecessor TOPEX/Poseidon. Although both missions have met prescribed error budgets, comparison of the mean and time-varying sea surface height profiles from near simultaneous observations derived from the missions' Geophysical Data Records exhibit significant basin scale differences. Several suspected sources causing this disagreement are identified and improved upon, including (a) replacement of TOPEX and Jason project POE with enhanced orbits computed at GSFC within a consistent ITRF2000 terrestrial reference frame, (b) application of waveform retracking corrections to TOPEX significant wave height and sea surface heights, (c) resultant improved efficacy of the TOPEX sea state bias estimation from the value added sea surface height, and (d) estimation of Jason-1 sea state bias employing dual TOPEX/Jason crossover and collinear sea surface height residuals unique to the validation mission. The resultant mean sea surface height comparison shows improved agreement at better than 60 percent level of variance reduction with a standard deviation less then 0.5 cm. 相似文献
9.
全球有效波高和风速的时空变化及相关关系研究 总被引：2，自引：1，他引：1
The climatology of significant wave height（SWH） and sea surface wind speed are matters of concern in the fields of both meteorology and oceanography because they are very important parameters for planning offshore structures and ship routings. The TOPEX/Poseidon altimeter, which collected data for about 13 years from September 1992 to October 2005, has measured SWHs and surface wind speeds over most of the world＇s oceans. In this paper, a study of the global spatiotemporal distributions and variations of SWH and sea surface wind speed was conducted using the TOPEX/Poseidon altimeter data set. The range and characteristics of the variations were analyzed quantitatively for the Pacific, Atlantic, and Indian oceans. Areas of rough waves and strong sea surface winds were localized precisely, and the correlation between SWH and sea surface wind speed analyzed. 相似文献
10.
Eight years of sea surface height data derived from the TOPEX/Poseidon altimeter, are analyzed in order to identify long- and a-periodic behavior of the North Atlantic sea level. For easy interpolation, sea surface height data are converted into sea surface topography data using the geoid derived from EGM96 to degree 360. Principal Component Analysis is used to identify the most dominant spatial and temporal variations. In order to separate dominant periodic signals, a yearly and a half-yearly oscillation, as well as alias effects from imperfect ocean tide corrections, are estimated independently by a Harmonic Analysis and subtracted. The residuals are smoothed by a 90-day moving average filter and examined once again by a PCA, which identifies a low-frequency variation with a period of approximately 6–7 years and an amplitude of about 1 dm, as well as a large sea level change of partially more than ±1 dm within only few months. This sea level change can also be seen in yearly and seasonal sea level residuals. Furthermore, the analysis shows a significant sea level change in 1998 occurring almost over the whole North Atlantic, which is not clearly identified by the PCA. Similar results are obtained by analyzing sea surface temperature and sea level pressure data. 相似文献
11.
The long-term sea-level trend in the Bering Sea is obtained by the analysis of TOPEX/Poseidon altimeter data, including the data of two tide gauges. The averaged sea-level in the Bering Sea rises at a rate of 2.47 mm/a from 1992 to 2002. The mean sea-level is falling in the most part of the Bering Sea, especially in its central basin, and it is rising in the northeastern part of the Bering Sea. During the 1998/99 change, the sea-level anomaly differences exhibit a significant sea-level anomaly fall in the deep basin of the Bering Sea,which is roughly in the same position where a prominent SST fall exists. The maximal fall of sea-level is about 10 cm in the southwestern part of the Bering Sea, and the maximal fall of about 2℃ in the SST also appeared in the same region as the sea level did.The steric sea-level change due to temperature variations is discussed. The results are compared with the TOPEX/Poseidon altimeter data at the different spatial scales. It is indicated that the seasonal amplitude of the steric height is about 35% of the observed TOPEX/Poseidon amplitude, which is much smaller than the 83% in the mid-latitudes area. The systematic difference between the TOPEX/Poseidon data with the range of about 7.5 cm and the thermal contribution with the range of about 2.5 cm is about 5 cm. This indicates that the thermal effect on the sea level is not as important as the case in the mid-latitudes area. In the Bering Sea, the phase of the steric height leads the observed sea level by about three months. 相似文献
12.
13.
Eight years of sea surface height data derived from the TOPEX/Poseidon altimeter, are analyzed in order to identify long- and a-periodic behavior of the North Atlantic sea level. For easy interpolation, sea surface height data are converted into sea surface topography data using the geoid derived from EGM96 to degree 360. Principal Component Analysis is used to identify the most dominant spatial and temporal variations. In order to separate dominant periodic signals, a yearly and a half-yearly oscillation, as well as alias effects from imperfect ocean tide corrections, are estimated independently by a Harmonic Analysis and subtracted. The residuals are smoothed by a 90-day moving average filter and examined once again by a PCA, which identifies a low-frequency variation with a period of approximately 6-7 years and an amplitude of about 1 dm, as well as a large sea level change of partially more than ±1 dm within only few months. This sea level change can also be seen in yearly and seasonal sea level residuals. Furthermore, the analysis shows a significant sea level change in 1998 occurring almost over the whole North Atlantic, which is not clearly identified by the PCA. Similar results are obtained by analyzing sea surface temperature and sea level pressure data. 相似文献
14.
《Marine Geodesy》2013,36(3-4):367-382
The verification phase of the Jason-1 satellite altimeter mission presents a unique opportunity for comparing near-simultaneous, independent satellite measurements. Here we examine simultaneous significant wave height measurements by the Jason-1 and TOPEX/Poseidon altimeters. These data are also compared with in situ measurements from deep-ocean buoys and with predicted wave heights from the Wave Watch III operational model. The rms difference between Jason and TOPEX wave heights is 28 cm, and this can be lowered by half through improved outlier editing and filtering of high-frequency noise. Noise is slightly larger in the Jason dataset, exceeding TOPEX by about 7 cm rms at frequencies above 0.05 Hz, which is the frequency at which the coherence between TOPEX and Jason measurements drops to zero. Jason wave heights are more prone to outliers, especially during periods of moderate to high backscatter. Buoy comparisons confirm previous reports that TOPEX wave heights are roughly 5% smaller than buoy measurements for waves between 2 and 5 m; Jason heights in general are 3% smaller than TOPEX. Spurious dips in the TOPEX density function for 3- and 6-m waves, a problem that has existed since the beginning of the mission, can be solved by waveform retracking. 相似文献
15.
The verification phase of the Jason-1 satellite altimeter mission presents a unique opportunity for comparing near-simultaneous, independent satellite measurements. Here we examine simultaneous significant wave height measurements by the Jason-1 and TOPEX/Poseidon altimeters. These data are also compared with in situ measurements from deep-ocean buoys and with predicted wave heights from the Wave Watch III operational model. The rms difference between Jason and TOPEX wave heights is 28 cm, and this can be lowered by half through improved outlier editing and filtering of high-frequency noise. Noise is slightly larger in the Jason dataset, exceeding TOPEX by about 7 cm rms at frequencies above 0.05 Hz, which is the frequency at which the coherence between TOPEX and Jason measurements drops to zero. Jason wave heights are more prone to outliers, especially during periods of moderate to high backscatter. Buoy comparisons confirm previous reports that TOPEX wave heights are roughly 5% smaller than buoy measurements for waves between 2 and 5 m; Jason heights in general are 3% smaller than TOPEX. Spurious dips in the TOPEX density function for 3- and 6-m waves, a problem that has existed since the beginning of the mission, can be solved by waveform retracking. 相似文献
16.
17.
Yu. V. Artamonov 《Physical Oceanography》2006,16(3):177-187
The monthly average values of the anomalies of the ocean level (according to the satellite data for 1992–2002) and the annual
average dynamic heights (hydrological data) are used to compute the seasonal cycle of geostrophic currents on the surface
of the Atlantic Ocean. It is shown that the west and east currents are intensified with a phase difference of several months.
At the same time, their latitudinal displacements are quasisynchronous. A delay of the seasonal signal in the east-west direction
of about 2–3 months (on the average) is typical of currents in the tropical zone of the Northern Hemisphere. On the contrary,
in the South Atlantic, the seasonal signal propagates in the west-east direction and its phase delay can be as large as almost
six months.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 3, pp. 60–71, May–June, 2006. 相似文献
18.
南海海面高度季节变化的数值模拟 总被引：8，自引：1，他引：8
比较POM模式模拟与观测(TOPEX/Poseidon高度计资料)的南海海面高度(SSH)的季节变化在空间分布上的一致性和差异.结果表明:本文使用的POM模式能较好地模拟南海SSH的季节变化;冬季与夏季,春季与秋季南海海面异常场形式完全相反,冬季Ekman输运造成在西海岸的堆积要比夏季在东海岸堆积更明显,而吕宋冷涡中心附近和吕宋海峡海面季节变化振幅最大;除春季以外,在南海绝大部分海域,海面高度的季节变化主要受风力的控制,南海海面热量通量对SSH的季节变化贡献约为20%,风应力对SSH的季节变化的贡献约为80%. 相似文献
19.
20.
热带大西洋表层环流及其月变化特征的分析 总被引：3，自引：0，他引：3
应用1993年4月至2001年3月的TOPEX/Poseidon卫星高度计遥感资料,分析了8 a平均热带大西洋(15°S～25°N,5°～50°W)表层环流结构的月变化特征.研究结果表明:热带大西洋表层环流中高纬度海区流速较小,赤道附近流速较大,表层环流系统大部分流系月变化不明显,部分流系月际波动较显著.具体来说,西南向的北赤道流下半年的纬向流速分量比上半年大.非洲沿岸流在5～11月流向为东北向,在其他月份主要为东南向.北赤道逆流可以分成两部分:25°W以东海区,北赤道逆流常年流向向东,到9月份前后流速达到最大值(约0.25 cm/s);25°W以西海区,7月至翌年1月流向向东,2～6月北赤道逆流减小,并有西向流产生.2°S～2°N,15°W以东海区的南赤道流在1～3月、9～10月流向向东,其他月份流向向西.南赤道流可认为是由南、北两支西向的海流构成,这两支海流的流轴分别位于6°S和1°N,在6～7月北支流速达到最大值0.6 m/s.南美洲纳塔耳东部西北向的北巴西海流流速月际变化不大,在5～6月份流速达到最大值0.3～0.4 m/s.相应的卫星风场遥感资料的分析表明热带大西洋表层环流结构的月变化特征与风场的分布及变化有较好的对应关系.用World Ocean Atlas 2001的月平均温盐数据反演出来的表层地转流场以及卫星跟踪ARGOS漂流浮标观测进行的对比验证表明,上述遥感分析的地转流场结果与水文数据以及海上观测结果一致. 相似文献