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1.
Quasi-stationary sea surface topography estimation by the multiple input/output method 总被引:1,自引:0,他引:1
Multiple input/multiple output system theory (MIMOST) is briefly presented, and the application of the method to the quasi-stationary
sea surface topography (QSST) estimation and the filtering of the input observations are discussed. The repeat character of
satellite altimetry missions provides more than one sample of the measured sea surface height (SSH) field, and an approximation
of the input signal and error power spectral densities can be determined using this successive information. A case study in
the Labrador Sea is considered using SSHs from ERS1 phases C and G, ERS1-GM, ERS2 phase A and TOPEX/POSEIDON altimetric missions
in combination with shipborne gravity anomalies. The time period of the observations in this study is from 1993 to 1998. Some
comparisons between the techniques used for the power spectral density approximation are carried out and some remarks on the
properties of the estimated QSST are presented.
Received: 19 October 1999 / Accepted: 23 October 2000 相似文献
2.
Global mean sea surface heights (SSHs) and gravity anomalies on a 2′×2′ grid were determined from Seasat, Geosat (Exact Repeat Mission and Geodetic Mission), ERS-1 (1.5-year mean of 35-day, and
GM), TOPEX/POSEIDON (T/P) (5.6-year mean) and ERS-2 (2-year mean) altimeter data over the region 0∘–360∘ longitude and –80∘–80∘ latitude. To reduce ocean variabilities and data noises, SSHs from non-repeat missions were filtered by Gaussian filters
of various wavelengths. A Levitus oceanic dynamic topography was subtracted from the altimeter-derived SSHs, and the resulting
heights were used to compute along-track deflection of the vertical (DOV). Geoidal heights and gravity anomalies were then
computed from DOV using the deflection-geoid and inverse Vening Meinesz formulae. The Levitus oceanic dynamic topography was
added back to the geoidal heights to obtain a preliminary sea surface grid. The difference between the T/P mean sea surface
and the preliminary sea surface was computed on a grid by a minimum curvature method and then was added to the preliminary
grid. The comparison of the NCTU01 mean sea surface height (MSSH) with the T/P and the ERS-1 MSSH result in overall root-mean-square
(RMS) differences of 5.0 and 3.1 cm in SSH, respectively, and 7.1 and 3.2 μrad in SSH gradient, respectively. The RMS differences
between the predicted and shipborne gravity anomalies range from 3.0 to 13.4 mGal in 12 areas of the world's oceans.
Received: 26 September 2001 / Accepted: 3 April 2002
Correspondence to: C. Hwang
Acknowledgements. This research is partly supported by the National Science Council of ROC, under grants NSC89-2611-M-009-003-OP2 and NSC89-2211-E-009-095.
This is a contribution to the IAG Special Study Group 3.186. The Geosat and ERS1/2 data are from NOAA and CERSAT/France, respectively.
The T/P data were provided by AVISO. The CLS and GSFC00 MSS models were kindly provided by NASA/GSFC and CLS, respectively.
Drs. Levitus, Monterey, and Boyer are thanked for providing the SST model. Dr. T. Gruber and two anonymous reviewers provided
very detailed reviews that improved the quality of this paper. 相似文献
3.
Gravity recovery using COSMIC GPS data: application of orbital perturbation theory 总被引:14,自引:0,他引:14
C. Hwang 《Journal of Geodesy》2001,75(2-3):117-136
COSMIC is a joint Taiwan–US mission to study the atmosphere using the Global Positioning System (GPS) occultation technique.
Improved formulas are developed for the radial, along-track, and cross-track perturbations, which are more accurate than the
commonly used order-zero formulas. The formulas are used to simulate gravity recovery using the geodetic GPS data of COSMIC
in the operational phase. Results show that the EGM96 model can be improved up to degree 26 using 1 year of COSMIC data. TOPEX/POSEIDON
altimeter data are used to derive a temporal gravity variation. COSMIC cannot reproduce this gravity variation perfectly because
of data noise and orbital configuration, but the recovered field clearly shows the gravity signature due to mass movement
in an El Ni?o.
Received: 3 March 2000 / Accepted: 10 November 2000 相似文献
4.
《地理信息系统科学与遥感》2013,50(4):242-257
The influence of regional features on the accuracy of single- and twoparameter algorithms for radioaltimeter determination of the speed of the near-surface wind over the ocean was investigated. The analysis was made using data from contact measurements (NDBC buoys) and the TOPEX/POSEIDON satellite radioaltimeter (wavelength 2.1 cm). It is shown that the nature of the waves, to a considerable degree related to regional conditions, exerts a strong influence on the accuracy in wind speed determination, resulting in an error in wind speed determination of 2-2.5 m/s. A new approach to the wind speed retrieval problem is proposed, making it possible to reduce the retrieval error to a level comparable with the best existing algorithms. 相似文献
5.
Seasonal sea level change from TOPEX/Poseidon observation and thermal contribution 总被引:10,自引:0,他引:10
J. L. Chen C. K. Shum C. R. Wilson D. P. Chambers B. D. Tapley 《Journal of Geodesy》2000,73(12):638-647
Seasonal steric sea-level change due to temperature variation in the mixing layer is assessed using space-measured sea-surface
temperature data and historical in situ temperature measurements. The results are compared with TOPEX/Poseidon satellite altimeter
measurement at different large spatial scales. It is indicated that thermal effect accounts for much of the observed seasonal
variability, especially when averaging over zonal regions. Some regional seasonal patterns of sea-level anomalies in the tropical
oceans are well represented by the thermal model prediction. Systematic differences are shown between TOPEX/Poseidon observation
and thermal contribution at a 1–2 cm level. The potential causes for these differences are discussed, including water mass
exchanges among the atmosphere, land, and oceans, and error sources in the steric result and geophysical corrections applied
in TOPEX/Poseidon data.
Received: 25 September 1998 / Accepted: 13 July 1999 相似文献
6.
A. J. E. Smith B. A. C. Ambrosius K. F. Wakker P. L. Woodworth J. M. Vassie 《Journal of Geodesy》1997,71(11):695-703
Three years of TOPEX/POSEIDON altimeter data have been processed at Delft Institute for Earth-Oriented Space Research (DEOS)
to solve the major diurnal and semi-diurnal constituents of the global ocean tide using the two classical methods of tidal
analysis, i.e. the harmonic and response analyses. Some experiments with the parameters in the response formalism show that the tidal admittance
in both the diurnal and semi-diurnal band can be adequately described with a lag interval of 2 days and a number of lags of
three. Results of both methods are evaluated from the differences with the most recent Grenoble hydrodynamic model (FES95.2)
and from the fit with the harmonic constants of a globally distributed set of tide gauges. It was found that the solutions
of the two methods differ at the millimeter level and are thus fully equivalent, which is confirmed by the tide gauges and
the differences with FES95.2. From the comparisons with the Grenoble model it was found that the M
2 and S
2 solutions of that model likely contain bathymetric errors which are of the order of 1–2 cm for M
2 and 0.5 cm for S
2.
Received: 18 December 1996 / Accepted: 12 May 1997 相似文献
7.
Aerosol and water vapour are very important element in the Earth’s climate system which has direct role in the Earth’s radiation budget. In this paper the seasonality, latitudinal distribution and the relationship of aerosol optical thickness (AOD) and water vapour (WV) using MODIS Level 3 monthly data from 2001 to 2008 are analysed. The analysis shows that AOD (0.55 μm) values reach maximum during southwest monsoon and remain minimum during northeast monsoon period. The Equatorial Indian Ocean shows minimum AOD (0.115 to 0.153) throughout the year compared to Arabian Sea (0.208 to 0.613) and Bay of Bengal (0.214 to 0.351). Arabian Sea shows high variation and maximum value of AOD compared to Bay of Bengal and Equatorial Indian Ocean. During southwest monsoon WV over Bay of Bengal was found higher in concentration compared to Arabian Sea and Equitorial Indian Ocean throughout the study period. Comparison between Arabian Sea (2.98 cm to 5.07 cm) and Bay of Bengal (3.49 cm to 5.94 cm) shows that WV concentration is less in Arabian Sea throughout the year. The analysis of correlation between WV and AOD was found to be inconsistent. However, AOD and WV shows a strong positive correlation for whole year (Mean R2 =0.90) in the Equitorial Indian Ocean region except in the months of January, February and March. In general, the correlation between WV and AOD is found to be strongly positive for oceanic aerosol (sea salt) in low water vapour condition. 相似文献
8.
由ERS-2和TOPEX卫星测高数据推算的海面高异常的主成分分析 总被引:1,自引:0,他引:1
利用1995~2003年间的TOPEX/POSEIDON和ERS-2卫星测高数据,尽量采用相同的改正模型对TOPEX和ERS-2卫星测高数据分别进行改正,然后由共线分析法分别推算了全球1°×1°的35 d的海面高异常时间序列,并采用主成分分析法分别对这两个海面高异常时间序列进行了分析。 相似文献
9.
M. C. Kim 《Journal of Geodesy》1997,71(12):749-767
The fundamental geometry of satellite ground tracks and their crossover problem are investigated. For idealized nominal ground
tracks, the geometry is governed by a few constant parameters whose variations lead to qualitative changes in the crossover
solutions. On the basis that the theory to locate crossovers has not been studied in sufficient detail, such changes are described
in regard to the number of crossover solutions in conjunction with their bifurcations. Employing the spinor algebra as a tool
for establishing the ground-track crossing condition, numerical methodologies to locate crossovers appearing in general dual-satellite
ground-track configurations are also presented. The methodologies are applied to precisely determined orbital ephemerides
of the GEOSAT, ERS-1, and TOPEX/POSEIDON altimeter satellites.
Received: 19 November 1996 / Accepted: 12 May 1997 相似文献
10.
由卫星测高数据观测到的印度洋海啸波高 总被引:4,自引:1,他引:4
本文介绍了利用卫星测高资料测定的印度洋地震引起的海啸波高的研究成果 ,以及卫星测高数据在对海啸灾害进行预测的应用价值。通过卫星雷达测高可观测到沿卫星星下点轨迹的相距几公里的点上的海面高 ,还提供了特别有价值的对海啸波的连续观测结果 相似文献
11.
Analysis of the bias between TOPEX and GPS vTEC determinations 总被引:4,自引:2,他引:2
The TOPEX/Poseidon satellite was jointly developed and deployed by the National Aeronautics and Space Administration (NASA),
USA, and the Centre National d’Etudes Spatiales (CNES), France (for details see Chelton et al. In: Fu L-L, Cazenave A (eds)
International geophysics series, vol 69, ISBN 0-12-269545-3, Academic Press, CA, pp 1–131, 2001), with the main scientific
goal of sea surface height monitoring. The process that ends with the TOPEX main observable (the range between the satellite
and the sea surface) involves the measurement of several parameters of the radar pulses reflected by the sea surface and the
computation of several other corrections. After several calibration campaigns performed by the Calibration/Validation team
of the mission, it was found that TOPEX range determinations were systematically shorter than expected and it was decided
to add an empirical correction of +15 mm to the TOPEX range-computation algorithm. As a by-product, TOPEX provides vertical
total electron content (vTEC) determinations which have turned out to be a very important data source for the ionospheric
research community. Since TOPEX vTEC measurements became available, several comparison studies have detected a constant bias,
from +2 to +5 TECu, when TOPEX is compared to other vTEC sources, e.g., Global Positioning System (GPS), Doppler Orbitography
and Radio-positioning Integrated by Satellite (DORIS), (TOPEX always greater than the others). In this work, we show that
miscalibration of the corrections used in the TOPEX processing algorithm can cause the shortening effect of TOPEX ranges and
at the same time the constant bias on the TOPEX vTEC values. It is also shown that changes on TOPEX System Biases of less
than 10 mm for the Ku-band and between 40 and 70 mm for the C-band, can make both effects disappear. The analyzed hypothesis
is supported by theoretical considerations and data analysis available in the specialized literature.
On behalf of the authors of the contribution ‘Analysis of the bias between TOPEX and GPS vTEC determinations’, I declare that
the paper has not been, nor is in the process of being published in any other publication. 相似文献
12.
Comparison of Inherent Optical Properties (IOPs) in Open and Coastal Waters of Arabian Sea Using In-Situ Bio-Optical Data 总被引:1,自引:0,他引:1
P. V. Nagamani Prakash Chauhan Nivedita Sanwlani 《Journal of the Indian Society of Remote Sensing》2011,39(4):455-462
The two main inherent optical properties (IOPs) namely absorption and back scattering coefficients were estimated using a
quasi analytical algorithm (QAA) for open and coastal ocean waters of Arabian Sea. Absorption due to gelbstoff and back scattering
due to the particulate matter were calculated using the quasi analytical algorithm for all the in-situ measured reflectance
spectra collected in the Arabian Sea. A comparative study was made to study the spectral variability of reflectance spectra
in open as well as coastal waters of Arabian Sea. Spectral analysis was made for the absorption and back scattering coefficients
calculated using the QAA for both open and coastal waters. The absorption coefficient in the open ocean waters vary from a
minimum value of 0.029 to a maximum value of 0.445 and it varies from a minimum value of 0.081 to a maximum value of 4.000
for the coastal waters of Arabian Sea. Absorption due to gelbstoff or the CDOM ag(λ), calculated for the Arabian Sea waters show a variation of 0.000202 to 0.112437 for open ocean waters and it varies from
0.002848 to 2.8936 for coastal waters of Arabian Sea. Particulate back scattering coefficient for open ocean waters vary from
0.0000307 to 0.006575 whereas bbp(λ) vary from 0.000167 to 0.026014 for coastal ocean waters. The minimum slope for the open ocean waters is 0.989 and maximum
value of 2.147 (average value of 1.7) was observed; whereas a minimum value of 0.046 and a maximum value of 1.201 (average
value of 0.6) were observed from the in-situ spectra for coastal waters of Veraval. The slope ‘Y’ estimated from the model
is 1.957 for open ocean waters and 0.515 for coastal waters collected in the Arabian Sea. 相似文献
13.
On monitoring a vertical datum with satellite altimetry and water-level gauge data on large lakes 总被引:3,自引:0,他引:3
Using TOPEX satellite altimetry, water-level-gauge data, and a geoid model, the geopotential, W
0, of the International Great Lakes Datum of 1985 (IGLD85) is determined. This is compared to an analogous determination using GPS and leveling data in the region. The two sets of data yield generally consistent results at the few-decimeter level and both indicate a tilt of about 33 cm in the computed datum across the region. On the basis of this and other studies, it is conjectured that the source of the tilt is a regional error in G99SSS. Further analysis of the altimetry and water-level data indicate that the geoid model, G99SSS, is in error by up to 20 cm at scales of about 100–150 km. In addition, the analysis of 8 years of altimeter and water-level data shows varying trends (up to 2 mm/yr) in crustal uplift throughout the region, generally consistent with an independent post-glacial rebound (PGR) model, ICE-4G.
AcknowledgmentThis research was supported in part by the Ohio Sea Grant Program, grant no. NA86RG0053 (R/CE-5). A. Mainville kindly provided data and information for Canadian stations. The authors are grateful to M. Bursa, M. Poutanen, D. Zilkoski, and an anonymous reviewer for contributing significantly to the improvement of the paper. 相似文献
14.
Region-specific atmospheric range correction maps are generated over the Indian tropical region from Jason-1 & Jason-2 radar altimeters data. Seasonal and spatial variability of wet tropospheric correction (WTC), ionospheric correction (IC), dry tropospheric correction (DTC), and sea state bias (SSB) correction are analyzed over the Bay of Bengal and the Arabian Sea. Two year atmospheric range correction data from JASON-1 (2008) & JASON-2 altimeters (2009) has been analyzed where each Jason cycle is exactly 9.9156?days repeat. The monthly and yearly mean variation of the range correction parameters has been studied over the Indian continent. For precise study, four different regions were selected as the Region of Interest in the North & South of the Arabian Sea and Bay of Bengal. WTC, Significant Wave Height (SWH), Wind Speed (WS) and SSB show the higher values during monsoon months. The yearly mean WTC over Indian Tropical region was 26.22?cm in 2008 and 26.20?cm in 2009. SSB Correction values mainly depend on the SWH and wind speed. The yearly mean SSB correction over Indian Tropical region was 6.87?cm in 2008 and 7.02?cm in 2009. DTC values are less during monsoon season and it shows a high value in the month of January. The yearly mean DTC over Indian Tropical region was 230.42?cm in 2008 and 230.43?cm in 2009.The IC values mainly depend on frequency and total electron content (TEC) in the ionosphere which further depends on the solar activity. The yearly mean IC over Indian Tropical region was higher in 2008 (2.98?cm) in comparison to mean IC in 2009 (2.29?cm). This study is useful to understand the variability of atmospheric correction parameters especially over Indian continent. 相似文献
15.
A technique is presented for the development of a high-precision and high-resolution mean sea surface model utilising radar
altimetric sea surface heights extracted from the geodetic phase of the European Space Agency (ESA) ERS-1 mission. The methodology
uses a cubic-spline fit of dual ERS-1 and TOPEX crossovers for the minimisation of radial orbit error. Fourier domain processing
techniques are used for spectral optimal interpolation of the mean sea surface in order to reduce residual errors within the
initial model. The EGM96 gravity field and sea surface topography models are used as reference fields as part of the determination
of spectral components required for the optimal interpolation algorithm. A comparison between the final model and 10 cycles
of TOPEX sea surface heights shows differences of between 12.3 and 13.8 cm root mean square (RMS). An un-optimally interpolated
surface comparison with TOPEX data gave differences of between 15.7 and 16.2 cm RMS. The methodology results in an approximately
10-cm improvement in accuracy. Further improvement will be attained with the inclusion of stacked altimetry from both current
and future missions.
Received: 22 December 1999 / Accepted: 6 November 2000 相似文献
16.
We can presently construct two independent time series of sea level, each at a precision of a few centimeters, from Geosat
(1985–1988) and TOPEX/Poseidon (1992–1995) collinear altimetry. Both are based on precise satellite orbits computed using
a common geopotential model, JGM-2 (Nerem et al. 1994). We have attempted to connect these series using Geosat-T/P crossover
differences in order to assess long-term ocean changes between these missions. Unfortunately, the observed result are large-scale
sea level differences which appear to be due to a combination of geodetic and geopotential error sources. The most significant
geodetic component seems to be a coordinate system bias for Geosat sea level (relative to T/P) of −7 to −9 cm in the y-axis (towards the Eastern Pacific). The Geosat-T/P sea height differences at crossovers (with JGM-2 orbits) probably also
contain stationary geopotential-orbit error of about the same magnitude which also distort any oceanographic interpretation
of the observed changes. We also found JGM-3 Geosat orbits have not resolved the datum errors evident from the JGM-2 Geosat
-T/P results. We conclude that the direct altimetric approach to accurate determination of sea level change using Geosat and
T/P data still depends on further improvement in the Geosat orbits, including definition of the geocenter.
Received: 11 March 1996; Accepted: 19 September 1996 相似文献
17.
This study evaluates the performance of two widely used GRACE solutions (CNES/GRGS RL02 and CSR RL04) in deriving annual and
inter-annual water mass variations in the Black Sea for the period 2003–2007. It is demonstrated that the GRACE derived water
mass variations in the Black Sea are heavily influenced by the leakage of hydrological signals from the surrounding land.
After applying the corresponding correction, we found a good agreement with water mass variations derived from steric-corrected
satellite altimetry observations. Both GRACE and altimetry show significant annual water mass variations of roughly 7 cm amplitude
peaking in May and a semi-annual signal of roughly 3 cm peaking in June and in December. The amplitude of the annual water
mass signal varies significantly from year to year and is significantly larger during 2004–2006 than in 2003 and 2007. This
is also in agreement with the steric corrected altimetry. 相似文献
18.
A. I. Ginzburg A. G. Kostyanoy N. P. Nezlin D. M. Solov'yev R. R. Stanichnaya S. V. Stanichnyy 《地理信息系统科学与遥感》2013,50(2):130-143
A series of infrared NOAA satellite images of the northwestern Black Sea (resolution 1 km) and corresponding maps of chlorophyll “a” (SeaWiFS data, resolution 9 km) are analyzed for the period 1 June-28 August 1998. A major objective was detection of the movement of three synoptic-scale anticyclonic eddies over the continental slope and the entrainment of photopigment-rich coastal waters by them. The study examines the effects of wind direction on the visibility of eddies in the chlorophyll field, and attempts to identify conditions favoring the transport of chlorophyll-rich shelf waters into the sea's abyssal basin. 相似文献
19.
卫星测高数据的沿轨迹重力异常反演法及其应用 总被引:10,自引:0,他引:10
本文给出了一套基于直角坐标系下的垂线偏差求解重力异常公式 ,并将之发展成为一套新的沿轨迹重力异常求解公式。与其他方法相比 ,本方法无须求解交叠点处沿轨迹和跨轨迹方向的海面高斜率 ,仅需计算沿轨迹方向的海面高斜率 ,因而更为简洁、有效 ,而且分辨率可以更高并可与真正的沿航迹实际船测重力相比较、验证。据此 ,利用 Geosat/GM、ERS-1 /35天及TOPEX/Poseidon三种测高数据 ,反演了南中国海域 (0°~ 2 5°N,1 0 5°~ 1 2 2°E)的 2′× 2′重力异常—— IGG-S。通过与实际船测资料和国际同行提供的重力模型相比 ,IGG-S总体精度达到1 0× 1 0 - 5ms- 2。 相似文献
20.
Analysis of some systematic errors affecting altimeter-derived sea surface gradient with application to geoid determination over Taiwan 总被引:3,自引:1,他引:3
C. Hwang 《Journal of Geodesy》1997,71(2):113-130
This paper analyzes several systematic errors affecting sea surface gradients derived from Seasat, Geosat/ERM, Geosat/GM,
ERS-1/35d, ERS-1/GM and TOPEX/POSEIDON altimetry. Considering the data noises, the conclusion is: (1) only Seasat needs to
correct for the non-geocentricity induced error, (2) only Seasat and Geosat/GM need to correct for the one cycle per revolution
error, (3) only Seasat, ERS-1/GM and Geosat/GM need to correct for the tide model error; over shallow waters it is suggested
to use a local tide model not solely from altimetry. The effects of the sea surface topography on gravity and geoid computations
from altimetry are significant over areas with major oceanographic phenomena. In conclusion, sea surface gradient is a better
data type than sea surface height. Sea surface gradients from altimetry, land gravity anomalies, ship gravity anomalies and
elevation data were then used to calculate the geoid over Taiwan by least-squares collocation. The inclusion of sea surface
gradients improves the geoid prediction by 27% when comparing the GPS-derived and the predicted geoidal heights, and by 30%
when comparing the observed and the geoid-derived deflections of the vertical. The predicted geoid along coastal areas is
accurate to 2 cm and can help GPS to do the third-order leveling.
Received 22 January 1996; Accepted 13 September 1996 相似文献