SAR high-precision inversion of sea surface current over offshore China

doi:10.11947/j.AGCS.2026.20250444

Abstract

Abstract:

Sentinel-1 synthetic aperture radar (SAR) level-2 radial velocity (RVL) products have significantly enhanced the capacity to monitor and quantify mesoscale and sub-mesoscale ocean current features. However, challenges remain in large-scale, high-precision SAR current mapping and systematic multi-source validation within the complex dynamic systems of offshore China. To address these issues, this study performed non-geophysical and geophysical error corrections on all Sentinel-1 RVL data covering offshore China in 2021, generating a high-precision monthly surface current monitoring product. Furthermore, multi-source data, including in-situ station observations, hybrid coordinate ocean model (HYCOM) reanalysis, and Himawari-8(H-8) derived currents, were utilized to systematically evaluate the stability, applicability, and structural characterization capabilities of SAR-derived currents. The results indicate significant spatial heterogeneity in current velocity across offshore China, characterized by the highest velocities in the South China Sea, followed by the East China Sea, and the lowest in the Bohai and Yellow Seas. Current directions are primarily governed by the East Asian monsoon, exhibiting a typical monsoon-driven circulation pattern: overall northward/northeastward in winter and reversing to northward/northeastward in summer. Validation shows that SAR currents achieve good consistency with in-situ data, with a mean bias of 0.08 m/s and a correlation coefficient of 0.58. Compared to HYCOM and H-8 products, SAR is more sensitive to localized high-speed flows and sub-mesoscale structures, enabling a refined depiction of complex flow fields. The high-precision mapping and multi-source validation framework established in this study effectively enhances current monitoring capabilities in complex coastal environments and provides a scientific basis and technical support for the operational application of SAR ocean current products.

Key words: SAR RVL error correction, current retrieval in offshore China, monthly-scale current patterns, multi-source data cross-validation

CLC Number:

P229

Hongmei WANG, Lihua WANG, Benhua TAN, Xiaoyi JIANG, Lili SONG, Weiwei SUN. SAR high-precision inversion of sea surface current over offshore China[J]. Acta Geodaetica et Cartographica Sinica, 2026, 55(4): 588-603.

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69轨道影像日期	样本点数量	径向流速均值/（m/s）
69轨道影像日期	样本点数量	校正前	校正后
2021-01-06	231 718	－0.62	－0.32
2021-01-18	231 244	－0.65	－0.31
2021-01-30	231 175	－0.50	－0.31
2021-02-11	230 698	－0.19	－0.43
2021-02-23	231 290	－0.98	－0.53
2021-03-07	231 508	－0.39	－0.30
2021-03-19	229 419	0.04	－0.05
2021-03-31	228 082	0.39	0.00
2021-04-12	229 656	0.07	－0.03
2021-04-24	231 331	－0.42	－0.48
2021-05-06	229 204	0.39	－0.18
2021-05-18	226 262	0.68	0.18
2021-05-30	226 097	0.32	0.11
2021-06-11	228 428	0.32	0.01
2021-06-23	226 100	0.12	－0.29
2021-07-05	230 067	0.63	－0.24
2021-07-17	230 637	－0.57	－0.17
2021-07-29	229 606	0.60	0.53
2021-08-10	230 643	0.61	0.47
2021-08-22	228 044	0.40	0.33
2021-09-03	227 244	0.11	0.02
2021-09-27	228 210	－0.29	－0.24
2021-10-09	231 976	－0.61	－0.37
2021-10-21	231 940	－0.40	－0.22
2021-11-02	230 555	－1.27	－0.54
2021-11-14	216 620	－1.30	－0.47
2021-11-26	219 447	－1.34	－0.35
2021-12-08	219 385	－1.23	－0.36
2021-12-20	215 697	－1.01	－0.19