# Study on the Elimination Method of Wind Field Influence in Retrieving a Sea Surface Current Field
## 7 Conclusions  
ATI will be an important approach for observing the sea surface current field in the future. The Doppler velocity measured by ATI includes not only the sea surface current field but also complex interference factors, such as the wind-driven current, sea waves, and Bragg wave phase velocity. Removing these interference factors is the key to retrieving the ATI ocean current field. These interference factors are mainly related to the wind field. In previous studies, external wind field data sources (such as ECWMF) were used, and M4S and other models were employed to calculate and correct the interference factors. However, these external wind field data sources are often the average results of a large range in time and space, while the data obtained by SAR are second-level transient images, which do not match each other. In this paper, the wind field based on SAR data retrieval was used as parameter input, and the CDOP model was adopted to obtain interference factors to correct the ATI Doppler velocity. The experimental results show that the corrected current field results based on the wind field retrieved from SAR data were closer to those obtained by the shore-based radar than those obtained using ECWMF wind field data.  
A sea surface current observation experiment in the ATI experimental mode of the GF\(-\)3 satellite was performed in Qingdao, China, on 29 January 2022. The one-dimensional sea surface current field was extracted based on satellite data. The accuracy of the surface current inversion in the Qingdao sea obtained on 30 January 2022 was evaluated by comparing it with the HFSWR data. The statistics of the two flows showed good agreement. In our study, two input wind fields were considered, and the experimental results indicated that the GF\(-\)3 ATI current processed by the retrieved wind field agreed well with the HFSWR data. The wind field correction result based on the SAR retrieved wind field was closer to the current field measured by the shore-based HF radar than the wind field correction result obtained based on the ECMWF wind field.  
The wind field was input into the CDOP model, and then the Doppler anomaly output from this model was subtracted. The research method used in this paper is feasible in theory, but it still has some defects. First, in the phase error correction, only some estimation processing is conducted, and its accuracy is limited. In the ATI-SAR system, phase error can be caused by the antenna phase center error, antenna pointing error, satellite platform flight attitude error, etc. There are also errors in the received echo data. For the verification data (HFSWR data), due to the difference in the working system, the existing measurement methods, and data processing methods, errors inevitably appear in the verification of  
Figure 13: Scatter diagrams of GF\(-\)3 ATI currents processed with the ECWMF wind field versus the HFSWR data for the two scenes: (**a**) represents scene b; (**b**) represents scenes c in the Figure 1.  
the oceanic flow field. Therefore, scene error correction of radar measurement remains challenging, and further research on oceanic flow field inversion is needed.  
Conceptualization, X.W.; Project administration, B.H.; Writing--original draft, J.W.; Writing--review & editing, X.Y. and J.W. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the China High-Resolution Earth Observation System Program under Grant No. 41-Y30F07-9001-20/22.  
Not applicable.  
The authors declare no conflict of interest.