Analysis on the Accuracy of Marine Gravity Inversion from the Wide-swath Altimeter Mission

2020 ◽  
Author(s):  
Mao Zhou ◽  
Taoyong Jin ◽  
Jiancheng Li ◽  
Shengjun Zhang ◽  
Minzhang Hu
Keyword(s):  
Sea Surface Height ◽  
Sea Surface ◽  
Gravity Inversion ◽  
Vertical Deflection ◽  
The North ◽  
Marine Gravity ◽  
The Indian Ocean ◽  
Ocean Topography ◽  
East West ◽  
Wide Swath

<p>Marine gravity is mainly inversed by the nadir satellite altimetry observations. However, the accuracy of the east-west component of vertical deflection is significantly lower than the north-south component. The wide-swath altimeter is one of the main altimetry missions in the future. Its two-dimensional design is expected to obtain high-precision and high-resolution sea surface height simultaneously, and to improve the accuracy of the marine gravity inversion. Taking the SWOT (Surface Water and Ocean Topography) wide-swath altimeter mission as an example, based on the parameters including the ground track and the width of swath, the static sea surface height observations of SWOT, as well as the nadir altimeter missions Jason-1/GM, Cryosat-2/LRM, and SARAL/GM were simulated. Then, the vertical deflections were calculated from above observations to analyze the ability of marine gravity inversion in the South China Sea and part of the Indian Ocean. Compared with EGM2008 model, the vertical deflections determined by one cycle of SWOT are better than the result determined by combining Jason-1/GM, Cryosat-2/LRM, and SARAL/GM. And the results determined by SWOT improve the accuracy of the east-west component of vertical deflection significantly. And then, several specific errors of SWOT satellite were simulated, and their influence on the determination of the vertical deflection was analyzed. It is noted that these errors have certain influence on the accuracy, but can be weakened by using a simple Gaussian filter. In addition, the influence of SWOT sea surface height resolution on the gravity field inversion was analyzed. As a result, under the premise of the designed accuracy and resolution of the SWOT mission, its observations can improve the quality of marine gravity inversion effectively.</p>

scholarly journals Influence of Sea State on Sea Surface Height Oscillation from Doppler Altimeter Measurements in the North Sea

2018 ◽  
Vol 10 (7) ◽  
pp. 1100 ◽  
Author(s):  
Ferdinando Reale ◽  
Fabio Dentale ◽  
Eugenio Carratelli ◽  
Luciana Fenoglio-Marc
Keyword(s):  
North Sea ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Sea State ◽  
The North ◽  
The North Sea

scholarly journals Recovering Marine Gravity Over the Gulf of Guinea From Multi-Satellite Sea Surface Heights

2021 ◽  
Vol 9 ◽  
Author(s):  
Richard Fiifi Annan ◽  
Xiaoyun Wan
Keyword(s):  
Gravity Field ◽  
Gravity Anomalies ◽  
Sea Surface ◽  
Shallow Waters ◽  
Gulf Of Guinea ◽  
Gravity Field Model ◽  
The North ◽  
Marine Gravity ◽  
Sea Surface Heights ◽  
East Component

A regional gravity field product, comprising vertical deflections and gravity anomalies, of the Gulf of Guinea (15°W to 5°E, 4°S to 4°N) has been developed from sea surface heights (SSH) of five altimetry missions. Though the remove-restore technique was adopted, the deflections of the vertical were computed directly from the SSH without the influence of a global geopotential model. The north-component of vertical deflections was more accurate than the east-component by almost three times. Analysis of results showed each satellite can contribute almost equally in resolving the north-component. This is attributable to the nearly northern inclinations of the various satellites. However, Cryosat-2, Jason-1/GM, and SARAL/AltiKa contributed the most in resolving the east-component. We attribute this to the superior spatial resolution of Cryosat-2, the lower inclination of Jason-1/GM, and the high range accuracy of the Ka-band of SARAL/AltiKa. Weights of 0.687 and 0.313 were, respectively, assigned to the north and east components in order to minimize their non-uniform accuracy effect on the resultant gravity anomaly model. Histogram of computed gravity anomalies compared well with those from renowned models: DTU13, SIOv28, and EGM2008. It averagely deviates from the reference models by −0.33 mGal. Further assessment was done by comparing it with a quadratically adjusted shipborne free-air gravity anomalies. After some data cleaning, observations in shallow waters, as well as some ship tracks were still unreliable. By excluding the observations in shallow waters, the derived gravity field model compares well in ocean depths deeper than 2,000 m.

Interannual Variability in Sea Surface Height at Southern Midlatitudes of the Indian Ocean

2021 ◽  
Vol 51 (5) ◽  
pp. 1595-1609
Author(s):  
Motoki Nagura ◽  
Michael J. McPhaden
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Sea Surface Height ◽  
Wind Forcing ◽  
Sea Surface ◽  
The South ◽  
South Indian Ocean ◽  
Eastern Boundary ◽  
South Indian ◽  
The Indian Ocean

AbstractThis study examines interannual variability in sea surface height (SSH) at southern midlatitudes of the Indian Ocean (10°–35°S). Our focus is on the relative role of local wind forcing and remote forcing from the equatorial Pacific Ocean. We use satellite altimetry measurements, an atmospheric reanalysis, and a one-dimensional wave model tuned to simulate observed SSH anomalies. The model solution is decomposed into the part driven by local winds and that driven by SSH variability radiated from the western coast of Australia. Results show that variability radiated from the Australian coast is larger in amplitude than variability driven by local winds in the central and eastern parts of the south Indian Ocean at midlatitudes (between 19° and 33°S), whereas the influence from eastern boundary forcing is confined to the eastern basin at lower latitudes (10° and 17°S). The relative importance of eastern boundary forcing at midlatitudes is due to the weakness of wind stress curl anomalies in the interior of the south Indian Ocean. Our analysis further suggests that SSH variability along the west coast of Australia originates from remote wind forcing in the tropical Pacific, as is pointed out by previous studies. The zonal gradient of SSH between the western and eastern parts of the south Indian Ocean is also mostly controlled by variability radiated from the Australian coast, indicating that interannual variability in meridional geostrophic transport is driven principally by Pacific winds.

scholarly journals Preliminary Evaluation and Correction of Sea Surface Height from Chinese Tiangong-2 Interferometric Imaging Radar Altimeter

2020 ◽  
Vol 12 (15) ◽  
pp. 2496
Author(s):  
Lin Ren ◽  
Jingsong Yang ◽  
Xiao Dong ◽  
Yunhua Zhang ◽  
Yongjun Jia
Keyword(s):  
Sea Surface Height ◽  
Sea Surface ◽  
Retrieval Algorithm ◽  
Preliminary Evaluation ◽  
Interferometric Imaging ◽  
Radar Altimeter ◽  
Sea State ◽  
Imaging Radar ◽  
Sea State Bias ◽  
Wide Swath

In this study, we performed preliminary comparative evaluation and correction of two-dimensional sea surface height (SSH) data from the Chinese Tiangong-2 Interferometric Imaging Radar Altimeter (InIRA) with the goal of advancing its retrieval. Data from the InIRA were compared with one-dimensional SSH data from the traditional altimeters Jason-2, Saral/AltiKa, and Jason-3. Because the sea state bias (SSB) of distributed InIRA data has not yet been considered, consistency was maintained by neglecting the SSB for the traditional altimeters. The results of the comparisons show that the InIRA captures the same SSH trends as those obtained by traditional altimeters. However, there is a significant deviation between InIRA and traditional altimeter SSHs; consequently, systematic and parametric biases were analyzed. The parametric bias was found to be related to the incidence angles and a significant wave height. Upon correcting the two biases, the standard deviation significantly reduced to 8.1 cm. This value is slightly higher than those of traditional altimeters, which typically have a bias of ~7.0 cm. The results indicate that the InIRA is promising in providing a wide swath of SSH measurements. Moreover, we recommend that the InIRA retrieval algorithm should consider the two biases to improve SSH accuracy.

scholarly journals Dynamics of the seasonal variations in the Indian Ocean from TOPEX/POSEIDON sea surface height and an ocean model

1998 ◽  
Vol 25 (11) ◽  
pp. 1915-1918 ◽  
Author(s):  
Jiayan Yang ◽  
Lisan Yu ◽  
Chester J. Koblinsky ◽  
David Adamec
Keyword(s):  
Indian Ocean ◽  
Seasonal Variations ◽  
Sea Surface Height ◽  
Ocean Model ◽  
Sea Surface ◽  
The Indian Ocean

scholarly journals Adjusting altimetric sea surface height observations in coastal regions. Case study in the Greek Seas

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
Ioannis Mintourakis
Keyword(s):  
Satellite Altimetry ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Altimetry Data ◽  
Geoid Model ◽  
Sea Surface Topography ◽  
Marine Gravity ◽  
Mean Sea Surface ◽  
Process Strategy ◽  
Satellite Altimetry Data

AbstractWhen processing satellite altimetry data for Mean Sea Surface (MSS) modelling in coastal environments many problems arise. The degradation of the accuracy of the Sea Surface Height (SSH) observations close to the coastline and the usually irregular pattern and variability of the sea surface topography are the two dominant factors which have to be addressed. In the present paper, we study the statistical behavior of the SSH observations in relation to the range from the coastline for many satellite altimetry missions and we make an effort to minimize the effects of the ocean variability. Based on the above concepts we present a process strategy for the homogenization of multi satellite altimetry data that takes advantage ofweighted SSH observations and applies high degree polynomials for the adjustment and their uniffcation at a common epoch. At each step we present the contribution of each concept to MSS modelling and then we develop a MSS, a marine geoid model and a grid of gravity Free Air Anomalies (FAA) for the area under study. Finally, we evaluate the accuracy of the resulting models by comparisons to state of the art global models and other available data such as GPS/leveling points, marine GPS SSH’s and marine gravity FAA’s, in order to investigate any progress achieved by the presented strategy

Meridional Distribution of Surface CO2 along 67°E of the Indian Ocean

2020 ◽  
Author(s):  
Dong-Jin Kang ◽  
Sang-Hwa Choi ◽  
Daeyeon Kim ◽  
Gyeong-Mok Lee
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Surface Seawater ◽  
Surface Salinity ◽  
The North ◽  
The Indian Ocean ◽  
North And South

<p>Surface seawater carbon dioxide was observed from 3 °S to 27 °S along 67 °E of the Indian Ocean in April 2018 and 2019. Partial pressure of CO<sub>2</sub>(pCO<sub>2</sub>) in the surface seawater and the atmosphere were observed every two minutes using an underway CO2 measurement system (General Oceanics Model 8050) installed on R/V Isabu. Surface water temperature and salinity were measured as well. The pCO<sub>2</sub> was measured using Li-7000 NDIR. Standard gases were measured every 8 hours in five classes with concentrations of 0 µatm, 202 µatm, 350 µatm, 447 µatm, and 359.87 µatm. The fCO<sub>2</sub> of atmosphere remained nearly constant at 387 ± 2 µatm, but the surface seawater fCO<sub>2</sub> peaked at about 3 °S and tended to decrease toward the north and south. The distribution of fCO<sub>2</sub> in surface seawater according to latitude tends to be very similar to that of sea surface temperature. In order to investigate the factors that control the distribution of fCO<sub>2</sub> in surface seawater, we analyzed the sea surface temperature, sea surface salinity, and other factors. The effects of salinity are insignificant, and the surface fCO<sub>2</sub> distribution is mainly controlled by sea surface temperature and other factors that can be represented mainly by biological activity and mixing.</p>

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