Global ocean tides data were derived from Geosat altimeter data by means of the Quasi Harmonic Constituent Method (QHCM). Tidal solutions with resolution of 1°/3 in longitude and latitude were obtained for consti...Global ocean tides data were derived from Geosat altimeter data by means of the Quasi Harmonic Constituent Method (QHCM). Tidal solutions with resolution of 1°/3 in longitude and latitude were obtained for constituents M 2, S 2, O 1, K 1, M 4 and MS 4. The mean sea heights above the reference ellipsoid were also obtained consequently. The obtained tidal constants were compared with those from deep sea and island tide gauge data. The rms differences between the harmonic constants derived from Geosat altimetry and deep sea tide gauges for M 2, S 2, O 1 and K 1 ranged from 1.4 cm to 2.6 cm, although the GM altimeter data have significant errors due to instrument malfunction and other reasons. M 2 tide obtained was the most accurate one among all the tides. Comparison also showed that island tidal constants cannot represent well the tidal distribution in the ocean near the island, because of the significant local effect on tides.展开更多
Collinear analysis technique is widely used for determining sea surface variability with Geosat altimeter data from its Exact Repeat Mission (ERM). But most of the researches have been only on global scale or in ocean...Collinear analysis technique is widely used for determining sea surface variability with Geosat altimeter data from its Exact Repeat Mission (ERM). But most of the researches have been only on global scale or in oceans deeper than 2000 m In shallow shelf waters this method is hampered by the inaccuracy of ocean tide data supplied with Geosat Geophysical Data Records (GDRs). This work uses a modified collinear analysis technique characterized by simultaneous separation of mean sea level and ocean tide with the least squares method, to compute sea surface variability in the Northwest Pacific Ocean and eastern China Seas. The mean sea level map obtained contains not only bathymetric but also dynamic features such as amphidromes, indicating considerable improvement over previous works. Our sea surface variability maps show dearly the main current system, the well-known Zhejiang coastal upwelling, and a northern East China Sea meso-scale eddy in good agreement with satellite sea surface temperature (SST) bservation and historical in situ measurement. These all suggest that meaningful and reliable oceanographic results can still be achieved in shallow shelf waters from Geosat altimetry as long as proper data processing techniques are applied.展开更多
The Geosat altimeter ERM T2-GDRs data were used to analyze sea surface height (SSH) variabilities in the Northwest Pacific region of 10°- 45°N, 120°-- 160°E covering all the Kuroshio Current. After...The Geosat altimeter ERM T2-GDRs data were used to analyze sea surface height (SSH) variabilities in the Northwest Pacific region of 10°- 45°N, 120°-- 160°E covering all the Kuroshio Current. After processing the Geosat GDRs data, the 50 gridded SSH anomaly fields were acquired. The comparison between the SSH anomalies and tidal gauge sea levels showed that the altimeter data accorded with the tidal gauge data especially in the low frequency scale and in open sea. The mesoscale variability energy distribution obtained from the SSH anomalies was controlled by the position of the Kuroshio, bottom topography and the stationary meander of the Kuroshio. The relative transports of the Kuroshio Extension and the Kuroshio south of Japan, represented by the difference between the SSH anomalies on two sides of the current, had strong interannual and seasonal cycles, which was related to the Kuroshio large meander. When the Kuroshio meander occurred, the transport of the Kuroshio east of the Tokara Strait decreased, but that northeast of Taiwan Island increased. The variability of the transport east of the Philippines reflected the effects of the ENSO. The EOF analysis of the SSH anomaly fields showed that the first three EOFs accounted for 25.3%, 17.1 % and 13.7% of the total variance, and represented the meander mode, the ENSO mode and season mode respectively.展开更多
The geoid undulations in the Northwest Pacific were calculated by usingtheTopex/Poseidon and Geosataltimeter data. Firstly the bias between two types of the altimeter data was removed and the geoid undulations in the...The geoid undulations in the Northwest Pacific were calculated by usingtheTopex/Poseidon and Geosataltimeter data. Firstly the bias between two types of the altimeter data was removed and the geoid undulations in theNorthwest Pacific were acquired by a long wave bias diminishing model with a resolution of 30 km and precision of 14cm. Then an algorithm of inversion of gravity anomalies was derived , and the gravity anomalies in the East China Seawere calculated by using the algorithm and the geoid undulations. The rms of difference between the in situ measure-ments the gravity anomalies from altimeter data was 3 .8× 10-5 m/s2. A method to colculate the gravity anomaliesin a larger area was developed which combined gravity anomalies in four subregions overlapping each other into one data set in a larger region. The error analysys shaws that the model and result of the inversion of gravity anomalies were reliable.展开更多
文摘Global ocean tides data were derived from Geosat altimeter data by means of the Quasi Harmonic Constituent Method (QHCM). Tidal solutions with resolution of 1°/3 in longitude and latitude were obtained for constituents M 2, S 2, O 1, K 1, M 4 and MS 4. The mean sea heights above the reference ellipsoid were also obtained consequently. The obtained tidal constants were compared with those from deep sea and island tide gauge data. The rms differences between the harmonic constants derived from Geosat altimetry and deep sea tide gauges for M 2, S 2, O 1 and K 1 ranged from 1.4 cm to 2.6 cm, although the GM altimeter data have significant errors due to instrument malfunction and other reasons. M 2 tide obtained was the most accurate one among all the tides. Comparison also showed that island tidal constants cannot represent well the tidal distribution in the ocean near the island, because of the significant local effect on tides.
基金This Work was partly supported by the Youth Science Foundation of Ocean University of Qingdao.
文摘Collinear analysis technique is widely used for determining sea surface variability with Geosat altimeter data from its Exact Repeat Mission (ERM). But most of the researches have been only on global scale or in oceans deeper than 2000 m In shallow shelf waters this method is hampered by the inaccuracy of ocean tide data supplied with Geosat Geophysical Data Records (GDRs). This work uses a modified collinear analysis technique characterized by simultaneous separation of mean sea level and ocean tide with the least squares method, to compute sea surface variability in the Northwest Pacific Ocean and eastern China Seas. The mean sea level map obtained contains not only bathymetric but also dynamic features such as amphidromes, indicating considerable improvement over previous works. Our sea surface variability maps show dearly the main current system, the well-known Zhejiang coastal upwelling, and a northern East China Sea meso-scale eddy in good agreement with satellite sea surface temperature (SST) bservation and historical in situ measurement. These all suggest that meaningful and reliable oceanographic results can still be achieved in shallow shelf waters from Geosat altimetry as long as proper data processing techniques are applied.
基金supported by National spaceflight office of china.
文摘The Geosat altimeter ERM T2-GDRs data were used to analyze sea surface height (SSH) variabilities in the Northwest Pacific region of 10°- 45°N, 120°-- 160°E covering all the Kuroshio Current. After processing the Geosat GDRs data, the 50 gridded SSH anomaly fields were acquired. The comparison between the SSH anomalies and tidal gauge sea levels showed that the altimeter data accorded with the tidal gauge data especially in the low frequency scale and in open sea. The mesoscale variability energy distribution obtained from the SSH anomalies was controlled by the position of the Kuroshio, bottom topography and the stationary meander of the Kuroshio. The relative transports of the Kuroshio Extension and the Kuroshio south of Japan, represented by the difference between the SSH anomalies on two sides of the current, had strong interannual and seasonal cycles, which was related to the Kuroshio large meander. When the Kuroshio meander occurred, the transport of the Kuroshio east of the Tokara Strait decreased, but that northeast of Taiwan Island increased. The variability of the transport east of the Philippines reflected the effects of the ENSO. The EOF analysis of the SSH anomaly fields showed that the first three EOFs accounted for 25.3%, 17.1 % and 13.7% of the total variance, and represented the meander mode, the ENSO mode and season mode respectively.
文摘The geoid undulations in the Northwest Pacific were calculated by usingtheTopex/Poseidon and Geosataltimeter data. Firstly the bias between two types of the altimeter data was removed and the geoid undulations in theNorthwest Pacific were acquired by a long wave bias diminishing model with a resolution of 30 km and precision of 14cm. Then an algorithm of inversion of gravity anomalies was derived , and the gravity anomalies in the East China Seawere calculated by using the algorithm and the geoid undulations. The rms of difference between the in situ measure-ments the gravity anomalies from altimeter data was 3 .8× 10-5 m/s2. A method to colculate the gravity anomaliesin a larger area was developed which combined gravity anomalies in four subregions overlapping each other into one data set in a larger region. The error analysys shaws that the model and result of the inversion of gravity anomalies were reliable.
