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LANG Shuyan, HU Weiping, LI Xiuzhong, LI Yuyang, ZHAO Xinhua. Validation and Discrepancy Analysis of Sea Surface Mean Square Slope Measured by SWIM and CYGNSS (in Chinese). Chinese Journal of Space Science, 2026, 46(3): 1-8 doi: 10.11728/cjss2026.03.2025-0076
Citation: LANG Shuyan, HU Weiping, LI Xiuzhong, LI Yuyang, ZHAO Xinhua. Validation and Discrepancy Analysis of Sea Surface Mean Square Slope Measured by SWIM and CYGNSS (in Chinese). Chinese Journal of Space Science, 2026, 46(3): 1-8 doi: 10.11728/cjss2026.03.2025-0076
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Validation and Discrepancy Analysis of Sea Surface Mean Square Slope Measured by SWIM and CYGNSS

doi: 10.11728/cjss2026.03.2025-0076 cstr: 32142.14.cjss.2025-0076
  • 1.

    National Satellite Ocean Application Service, Beijing 100081

  • 2.

    School of Marine Sciences,Nanjing University of Information Science and Technology, Nanjing 210044

  • 3.

    Key Laboratory of Space Ocean Remote Sensing and Applications, Ministry of Natural Resources, Beijing 100081

  • 4.

    Jiangsu Marine Resources Development Research Institute, Jiangsu Ocean University, Lianyungang 222001

  • Received Date: 2025-05-12
  • Rev Recd Date: 2025-09-03
    • Available Online: 2025-09-12
    Abstract
  • The Mean Square Slope (MSS) of the sea surface is a key parameter for characterizing sea surface roughness in the field of marine microwave remote sensing, and it is of great significance for studying the air-sea coupling process and marine meteorological monitoring. This paper conducts a comparative analysis of the MSS retrieved by the Surface Waves Investigation and Monitoring (SWIM) on the China-France Oceanography Satellite (CFOSAT) and the Cyclone Global Navigation Satellite System (CYGNSS). SWIM retrieves the MSS by fitting the two-dimensional normalized radar backscatter cross-section under different incident angles and azimuth angles. CYGNSS obtains the MSS caused by local winds by subtracting a correction amount on the basis of preliminary observations. In this paper, after collocating the data from SWIM and CYGNSS in January 2023, a direct comparison has been made. It is found that the MSS derived from SWIM is higher than that retrieved by CYGNSS under low wind speeds, while when the wind speed exceeds approximately 7 m·s–1, the MSS derived from CYGNSS is higher than that given by SWIM. This is mainly attributed to the differences in the microwave bands of the two and the correction amount of the MSS generated by swell subtracted during the retrieval process of CYGNSS. After correcting the SWIM MSS using the Elfouhaily spectrum model, the bias between the two is approximately 0.03, and the random root mean square error is 0.0323. This error is caused by the MSS generated by swell and the differences in the cutoff wavelength. The research results clarify the differences and error sources of the MSS retrieved by the two spaceborne sensors, providing an important reference for the calibration of MSS data and subsequent marine research and applications.

     

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