Abstract
Chinese-French Oceanography Satellite (CFOSAT), the first satellite which can observe global ocean wave and wind synchronously, was successfully launched On 29 October 2018. The CFOSAT carries SWIM that can observe ocean wave on a global scale. Based on National Data Buoy Center (NDBC) buoys and Jason-3 altimeter data, this study evaluated the accuracy of L2 level products of CFOSAT SWIM from August 2019 to September 2020. The results show that the accuracy of the nadir Significant Wave Height (SWH) data of the SWIM wave spectrometer is good. Compared with the data of the NDBC buoys and Jason-3 altimeter, the RMSE of the nadir box SWH were 0.39 and 0.21 m, respectively. The variation trend of SWH were first increasing and then decreasing with the increasing of the wave height. The precision of off-nadir wave spectrum SWH is not better than nadir box SWH data. Accuracy was evaluated for off-nadir data from August 2019 to June 2020 and after June 2020, respectively. After linear regression correction, the accuracy of off-nadir wave spectrum SWH was improved. The data accuracy evaluation and comparison of different time period showed that the off-nadir wave spectrum SWH accuracy was improved after the data version was updated in June 2020, especially for 6° and 8° wave spectrum. The precision of off-nadir wave spectrum SWH decreases with the increasing of wave height. The accuracy of the dominant wave direction of each wave spectrum is also not very good, and the accuracy of the dominant wave direction of 10° wave spectrum is slightly better than the others. In general, the accuracy of SWIM nadir beam SWH data reaches the high data accuracy of traditional altimeter, while the accuracy of off-nadir wave spectrum SWH is less than that of nadir beam SWH data. The off-nadir SWH data accuracy after June 2020 has been greatly improved.
Highlights
Ocean wave is one of the important marine motion forms
Zieger et al verified the Significant Wave Height (SWH) data of the satellite radar altimeter in 23 years by using the buoy of the National Oceanic Data Center of the United States and concluded that their RMSE were all less than 0.25 m, and corrected the SWH data of the radar altimeter by using the correction equation [7]; Durrant et al evaluated the accuracy of Jason-1 altimeter by using the National Data Buoy Center (NDBC) buoy, and concluded that the overall root-mean-square error of the two was 0.227 m [8]; Chen et al used buoys and Jason-2 altimeter data to verify the accuracy of HY-2 altimeter SWH data, and concluded that the RMSE of HY-2 altimeter SWH was 0.33 m; the results showed that HY-2 altimeter and
Since Chinese-French Oceanography Satellite (CFOSAT)’s successful launch in 2018, Surface Wave Investigation and Monitoring (SWIM) has captured more than two years of global ocean wave observations
Summary
Ocean wave is one of the important marine motion forms. The parameters to describe ocean wave mainly include wave height, wavelength and direction, etc., and the sea state can be clearly described by using these parameters. Ocean wave parameters can be obtained by buoy observation or satellite remote sensing. The ocean wave data obtained by satellite altimeters cover a much larger area. Merle et al analyzed the wave spectrum observed by KuROS airborne synthetic pore radar and wave parameters and believed that this radar has a better accuracy in wave spectrum inversion for ocean wave with the main wave length less than 200 m, which is a powerful supplement to satellite and buoy data [11]. Used Parameterized First-guess Spectrum Method (PFSM) to estimate wave parameters from TerraSAR-X images, including SWH and MWP, and compared them with field buoy measurement results and Wavewatch-III model.
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