期刊
FRONTIERS IN EARTH SCIENCE
卷 10, 期 -, 页码 -出版社
FRONTIERS MEDIA SA
DOI: 10.3389/feart.2022.795935
关键词
mean dynamic topography; geostrophic current; signal reconstruction; Gulf stream; mean sea surface; global geopotential model; least squares
资金
- National Natural Science Foundation of China [42004008, 42004014]
- Postgraduate Research and Practice Innovation Program of Jiangsu Province [KYCX21_0530]
- Fundamental Research Funds for the Central Universities
- Guangxi Key Laboratory of Spatial Information and Geomatics [19-185-10-06]
- Natural Science Foundation of Jiangsu Province, China [BK20190498, BK20200530]
- National Key Research Development Program of China [2018YFC1503603]
- Foundation for Returned Overseas Chinese Scholars, Nanjing [B2004804]
- Chinese Scholarship Council [202006710169, 201306270014]
- [CNES-CLS15MSS/CNES-CLS18MDT]
- [41830110]
The study proposes a least squares-based approach to model mean dynamic topography signal, which performs better in recovering current signal compared to traditional isotropic filtering methods. Error analysis indicates errors are primarily concentrated near coastal regions.
The filtering procedure is usually mandatory for modeling mean dynamic topography (MDT) when a geodetic approach based on the Mean Sea Surface (MSS) and the Global Geopotential Model (GGM) is used. This is due to the inconsistent spectral contents between MSS and GGM. However, traditional isotropic filtering algorithms (e.g., Gaussian filter) consider neither the MDT locations nor their azimuth when smoothing the signal within the filtering radius. Hence, the isotropic filtering will attenuate the MDT signal near the current and filter the current signal into the surrounding ocean, which may lead to signal contamination and distortion. In this study, we set up a least squares-based (LS) approach to model MDT signal from the altimeter-derived MSS and geoid height using spherical harmonics from GGMs, where MDT is parameterized by Lagrange Basis Functions (LBFs). The design matrix is segmentally established, considering the error information of GGM in various spectral bands. Numerical experiments in the Gulf Stream show that applications of full error variance-covariance matrix or only diagonal error variance of GGM may have marginal effects on the MDT modeling. The MDT computed from this LS-based approach using the latest releases of Gravity Field and Steady-state Ocean Circulation Explorer (GOCE) geoid models, i.e., GO_CONS_GCF_2_DIR_R6 and Gravity Observation Combination 06s model (GOCO06s), have the best agreement with the comparison data, especially near the current region. Deduced geostrophic velocities based on the MDT solutions show that the LS-based approach recovers the current signal better than the Gaussian filtering by 1.8 cm/s. Estimated error map illustrates that errors are more concentrated near the coastal region.
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