Simulation of the Wide Swath Sea Surface Height Calibration Using GNSS Buoy Array

2020 ◽  
Author(s):  
Xi-Yu Xu
Keyword(s):  
Sea Surface Height ◽  
Sea Surface ◽  
Wide Swath

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.

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 Contribution of a constellation of two Wide-Swath Altimetry Missions to Global Ocean Analysis and Forecasting

2021 ◽  
Author(s):  
Mounir Benkiran ◽  
Pierre-Yves Le Traon ◽  
Gérald Dibarboure
Keyword(s):  
Forecast Error ◽  
Sea Surface Height ◽  
Ocean Dynamics ◽  
Sea Surface ◽  
Global Ocean ◽  
Ocean Data Assimilation ◽  
The One ◽  
Wide Swath

Abstract. Swath altimetry is likely to revolutionize our ability to monitor and forecast ocean dynamics. To meet the requirements of the EU Copernicus Marine Service, a constellation of two wide-swath altimeters is envisioned for the long-term (post-2030) evolution of the Copernicus Sentinel 3 topography mission. A series of Observing System Simulation Experiments is carried out to quantify the expected performances. The OSSEs use a state-of-the-art high resolution (1/12°) global ocean data assimilation system similar to the one used operationally by the Copernicus Marine Service. Flying a constellation of two wide-swath altimeters will provide a major improvement of our capabilities to monitor and forecast the oceans. Compared to the present situation with 3 nadir altimeters flying simultaneously, the Sea Surface Height analysis and 7-day forecast error will be globally reduced by about 50 %. With two wide-swath altimeters, the quality of Sea Surface Height 7-day forecasts is equivalent to the quality of SSH analysis errors from three nadir altimeters. Our understanding of ocean currents is also greatly improved (30 % improvements at the surface and 50 % at 300 m depth). The resolution capabilities will be drastically improved and will be closer to 100 km wavelength compared to about 250 km today. Flying a constellation of two wide-swath altimeters thus looks to be a very promising solution for the long-term evolution of the Sentinel 3 constellation and the Copernicus Marine Service.

scholarly journals Measurement of the Sea Surface Height with Airborne GNSS Reflectometry and Delay Bias Calibration

2021 ◽  
Vol 13 (15) ◽  
pp. 3014
Author(s):  
Feng Wang ◽  
Dongkai Yang ◽  
Guodong Zhang ◽  
Jin Xing ◽  
Bo Zhang ◽  
...  
Keyword(s):  
Wind Speed ◽  
Arrival Time ◽  
Elevation Angle ◽  
Satellite System ◽  
Sea Surface Height ◽  
Antenna Pattern ◽  
Sea Surface ◽  
Observation Method ◽  
Global Navigation Satellite ◽  
The Impact

Sea surface height can be measured with the delay between reflected and direct global navigation satellite system (GNSS) signals. The arrival time of a feature point, such as the waveform peak, the peak of the derivative waveform, and the fraction of the peak waveform is not the true arrival time of the specular signal; there is a bias between them. This paper aims to analyze and calibrate the bias to improve the accuracy of sea surface height measured by using the reflected signals of GPS CA, Galileo E1b and BeiDou B1I. First, the influencing factors of the delay bias, including the elevation angle, receiver height, wind speed, pseudorandom noise (PRN) code of GPS CA, Galileo E1b and BeiDou B1I, and the down-looking antenna pattern are explored based on the Z-V model. The results show that (1) with increasing elevation angle, receiver height, and wind speed, the delay bias tends to decrease; (2) the impact of the PRN code is uncoupled from the elevation angle, receiver height, and wind speed, so the delay biases of Galileo E1b and BeiDou B1I can be derived from that of GPS CA by multiplication by the constants 0.32 and 0.54, respectively; and (3) the influence of the down-looking antenna pattern on the delay bias is lower than 1 m, which is less than that of other factors; hence, the effect of the down-looking antenna pattern is ignored in this paper. Second, an analytical model and a neural network are proposed based on the assumption that the influence of all factors on the delay bias are uncoupled and coupled, respectively, to calibrate the delay bias. The results of the simulation and experiment show that compared to the meter-level bias before the calibration, the calibrated bias decreases the decimeter level. Based on the fact that the specular points of several satellites are visible to the down-looking antenna, the multi-observation method is proposed to calibrate the bias for the case of unknown wind speed, and the same calibration results can be obtained when the proper combination of satellites is selected.

The global structure of the annual and semiannual sea surface height variability from Geosat altimeter data

1992 ◽  
Vol 97 (C11) ◽  
pp. 17813-17828 ◽  
Author(s):  
Gregg A. Jacobs ◽  
George H. Born ◽  
Mike E. Parke ◽  
Patrick C. Allen
Keyword(s):  
Sea Surface Height ◽  
Global Structure ◽  
Sea Surface ◽  
Altimeter Data

Pacific Ocean deep sea surface height fluctuation

2007 ◽  
Author(s):  
Todd Holden ◽  
P. Marchese ◽  
G. Tremberger, Jr. ◽  
D. Cotten ◽  
T. D. Cheung ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Deep Sea ◽  
Sea Surface Height ◽  
Sea Surface

scholarly journals On the Relationship between Regional Ocean Heat Content and Sea Surface Height

2017 ◽  
Vol 30 (22) ◽  
pp. 9195-9211 ◽  
Author(s):  
John T. Fasullo ◽  
Peter R. Gent
Keyword(s):  
Time Scales ◽  
Low Frequency ◽  
Heat Content ◽  
Sea Surface Height ◽  
Ocean Heat Content ◽  
Ocean Dynamics ◽  
Sea Surface ◽  
Altimeter Data ◽  
Model Control ◽  
The Relationship

Abstract An accurate diagnosis of ocean heat content (OHC) is essential for interpreting climate variability and change, as evidenced for example by the broad range of hypotheses that exists for explaining the recent hiatus in global mean surface warming. Potential insights are explored here by examining relationships between OHC and sea surface height (SSH) in observations and two recently available large ensembles of climate model simulations from the mid-twentieth century to 2100. It is found that in decadal-length observations and a model control simulation with constant forcing, strong ties between OHC and SSH exist, with little temporal or spatial complexity. Agreement is particularly strong on monthly to interannual time scales. In contrast, in forced transient warming simulations, important dependencies in the relationship exist as a function of region and time scale. Near Antarctica, low-frequency SSH variability is driven mainly by changes in the circumpolar current associated with intensified surface winds, leading to correlations between OHC and SSH that are weak and sometimes negative. In subtropical regions, and near other coastal boundaries, negative correlations are also evident on long time scales and are associated with the accumulated effects of changes in the water cycle and ocean dynamics that underlie complexity in the OHC relationship to SSH. Low-frequency variability in observations is found to exhibit similar negative correlations. Combined with altimeter data, these results provide evidence that SSH increases in the Indian and western Pacific Oceans during the hiatus are suggestive of substantial OHC increases. Methods for developing the applicability of altimetry as a constraint on OHC more generally are also discussed.

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