scholarly journals Inversion and Validation of Improved Marine Gravity Field Recovery in South China Sea by Incorporating HY-2A Altimeter Waveform Data

2020 ◽  
Vol 12 (5) ◽  
pp. 802 ◽  
Author(s):  
Shengjun Zhang ◽  
Ole Baltazar Andersen ◽  
Xiangxue Kong ◽  
Hang Li
Keyword(s):  
South China Sea ◽  
Gravity Field ◽  
South China ◽  
Pass Filter ◽  
Gravity Field Model ◽  
Waveform Data ◽  
Low Pass Filter ◽  
China Sea ◽  
Gravity Field Recovery ◽  
Marine Gravity

HaiYang-2A (HY-2A, where ‘Haiyang’ means ‘Ocean’ in Chinese) has provided reliable sea surface height observations for gravity with uniform ocean data coverage on a global scale for more than 8 years, particularly with denser across track sampling during the geodetic mission since March 2016. This paper aims at modeling and evaluating the regional marine gravity field at 1′×1′ resolution by incorporating HY-2A altimeter waveform data from 7 complete 168-day cycles in the geodetic mission phase. Initial evaluation indicates that, firstly, the measurements in the geodetic mission stay at a consistent accuracy level with observations at the start-of-life stage according to statistics of discrepancies at crossover points cycle by cycle. Secondly, range precision improvement can be achieved using a two-pass weighted least-squares retracker. Thirdly, a downsampling procedure combined with a low-pass filter is designed for HY-2A 20 Hz data to obtain 5 Hz measurements with enhanced precision. We calculate the 1′×1′ marine gravity field model over the South China Sea area by using the EGM2008 model as a reference field with the remove/restore method. The verifications with published models and shipborne gravimetric data show that HY-2A GM data is capable of improving marine gravity field modeling. Results show slightly higher accuracy than other models with similar input datasets but not including HY-2A. The accuracy is also compared with the latest DTU17 and SIO V27.1 model.

scholarly journals Calculation of Deflection of Vertical and Gravity Anomalies Over the South China Sea Derived from ICESat-2 Data

2021 ◽  
Vol 9 ◽  
Author(s):  
Defu Che ◽  
Hang Li ◽  
Shengjun Zhang ◽  
Baodong Ma
Keyword(s):  
South China Sea ◽  
Gravity Field ◽  
South China ◽  
Gravity Anomalies ◽  
The South China Sea ◽  
The South ◽  
Meridional Component ◽  
China Sea ◽  
Marine Gravity ◽  
Deflection Of Vertical

The Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) satellite uses a synchronized multi-beam photon-counting method to collect data from three pairs of synchronous ground tracks. The sampling rate along the ground tracks is designed to be ∼0.7 m, much smaller than that used in conventional radar altimeters. Hence, it is reasonable to expect an improvement in marine gravity recovery over coastal zones using ICESat-2 data. ICESat-2 provides valid sea surface height (SSH) measurements and a standard data product (ATL12) over ocean areas. This led us to consider the possibility of investigating its ability to calculate the deflection of vertical (DOV) and marine gravity anomalies. We processed ATL12 data about 22 months over the South China Sea (0°–23°N, 103°–120°E) and verified the ability of ICESat-2 SSH measurements to be used in calculating directional components of DOV. The results show that the ICESat-2 SSH data have a similar centimeter-magnitude accuracy level as data from the Jason-2 satellite. Furthermore, the accuracy of cross-track deflection of vertical (CTDOV) calculations between non-identical side beams is lower. For along-track points, the difference in accuracy between the solution of the prime component and the meridional component is significantly reduced, the prime component accuracy is significantly better than the directional components of the gridded deflection of vertical (GDOV), although the enhancement is weak for the meridional component. We also implemented the inversion of the ICESat-2 single mission based on the inverse Vening Meinesz formula, and verified the capability of ICESat-2 gravity field detection using shipborne gravity measurements and XGM2019 gravity field model, and found that the accuracy is 1.35 mGal and 2.47 mGal, respectively. ICESat-2 deserves the attention of the altimetry community, and its advantages are expected to make it an alternative data source for multi-mission fusion inversion of the ocean gravity field in the future.

How HY-2A/GM altimeter performs in marine gravity derivation: assessment in the South China Sea

2019 ◽  
Vol 219 (2) ◽  
pp. 1056-1064 ◽  
Author(s):  
Chengcheng Zhu ◽  
Jinyun Guo ◽  
Cheinway Hwang ◽  
Jinyao Gao ◽  
Jiajia Yuan ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Gravity Anomalies ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Open Sea ◽  
Marine Gravity ◽  
Sea Surface Heights ◽  
The Difference

SUMMARY HY-2A is China's first satellite altimeter mission, launched in Aug. 2011. Its geodetic mission (GM) started from 2016 March 30 till present, collecting sea surface heights for about five 168-d cycles. To test how the HY-2A altimeter performs in marine gravity derivation, we use the least-squares collocation method to determine marine gravity anomalies on 1′ × 1′ grids around the South China Sea (covering 0°–30°N, 105°E–125°E) from the HY-2A/GM-measured geoid gradients. We assess the qualities of the HY-2A/GM-derived gravity over different depths and areas using the bias and tilt-adjusted ship-borne gravity anomalies from the U.S. National Centers for Environmental Information (NCEI) and the Second Institute of Oceanography, Ministry of Natural Resources (MNR) of P. R. China. The RMS difference between the HY-2A/GM-derived and the NCEI ship-borne gravity is 5.91 mGal, and is 5.33 mGal when replacing the HY-2A value from the Scripps Institution of Oceanography (SIO) V23.1 value. The RMS difference between the HY-2A/GM-derived and the MNR ship-borne gravity is 2.90 mGal, and is 2.76 mGal when replacing the HY-2A value from the SIO V23.1 value. The RMS difference between the HY-2A and SIO V23.1 value is 3.57 mGal in open sea areas at least 20 km far away from the coast. In general, the difference between the HY-2A/GM-derived gravity and ship-borne gravity decreases with decreasing gravity field roughness and increasing depth. HY-2A results in the lowest gravity accuracy in areas with islands or reefs. Our assessment result suggests that HY-2A can compete with other Ku-band altimeter missions in marine gravity derivation.

scholarly journals Basement structures from satellite-derived gravity field: South China Sea ridge

2006 ◽  
Vol 111 (B5) ◽  
pp. n/a-n/a ◽  
Author(s):  
Carla Braitenberg ◽  
Susann Wienecke ◽  
Yong Wang
Keyword(s):  
South China Sea ◽  
Gravity Field ◽  
South China ◽  
China Sea ◽  
Basement Structures

On the modification of operational oceanography forecasting system for South China Sea in National Marine Environmental Forecasting Center of China

2020 ◽  
Author(s):  
Ziqing Zu ◽  
Xueming Zhu ◽  
Hui Wang
Keyword(s):  
South China Sea ◽  
South China ◽  
Optimal Interpolation ◽  
Physical Parameters ◽  
Background Error ◽  
Pass Filter ◽  
China Sea ◽  
Operational Oceanography ◽  
Forecasting System ◽  
Marine Environmental

<p>Based on ROMS and Ensemble Optimal Interpolation (EnOI) method, the South China Sea operational Oceanography Forecasting System (SCSOFS) is implemented in National Marine Environmental Forecasting Center (NMEFC), to provide the forecast of the currents, temperature and salinity in South China Sea for the future 5 days. Recently, a systematic modification has been carried out to SCSOFS to improve its forecast skill.</p><p>For the data assimilation system, new methods have been implemented, such as using Increment Analysis Update (IAU) and First Guess at Appropriate Time (FGAT), using a high-pass filter to evaluate the background error, assimilating multi-source observations, using non-uniform localization radius. In addition, the respective contribution of each method will also be discussed.</p><p>An optimization system is implemented for evaluating the values of physical parameters in ROMS, to remove the long-term bias of simulation. Argo temperature profiles is assimilated in the first half of 2017, to obtain the optimal coefficients of horizontal/vertical viscosity/diffusion and linear bottom drag. An independent validation from July of 2017 to December of 2018 shows that the simulation is improved using the optimal values.</p>

scholarly journals Calculating the Marine Gravity Anomaly of the South China Sea based on the Inverse Stokes Formula

2016 ◽  
Vol 46 ◽  
pp. 012062
Author(s):  
Liang Liu ◽  
Xiaoguang Jiang ◽  
Shanwei Liu ◽  
Lei Zheng ◽  
Jinxia Zang ◽  
...  
Keyword(s):  
South China Sea ◽  
Gravity Anomaly ◽  
South China ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Marine Gravity ◽  
Stokes Formula

Marine gravity determined from multi-satellite GM/ERM altimeter data over the South China Sea: SCSGA V1.0

2020 ◽  
Vol 94 (5) ◽  
Author(s):  
Chengcheng Zhu ◽  
Jinyun Guo ◽  
Jinyao Gao ◽  
Xin Liu ◽  
Cheinway Hwang ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
The South China Sea ◽  
Altimeter Data ◽  
The South ◽  
China Sea ◽  
Marine Gravity
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