Preliminary Significant Wave Height Retrieval from Interferometric Imaging Radar Altimeter Aboard the Chinese Tiangong-2 Space Laboratory
The interferometric imaging radar altimeter (InIRA) aboard the Chinese Tiangong-2 space laboratory is the first spaceborne imaging radar working at low incidence angles. This study focuses on the retrieval of significant wave heights (SWHs) from InIRA data. The retrieved SWHs can be used for correct...
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MDPI AG
2021-06-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/13/12/2413 |
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| author | Lin Ren Jingsong Yang Xiao Dong Yongjun Jia Yunhua Zhang |
| author_facet | Lin Ren Jingsong Yang Xiao Dong Yongjun Jia Yunhua Zhang |
| author_sort | Lin Ren |
| collection | DOAJ |
| description | The interferometric imaging radar altimeter (InIRA) aboard the Chinese Tiangong-2 space laboratory is the first spaceborne imaging radar working at low incidence angles. This study focuses on the retrieval of significant wave heights (SWHs) from InIRA data. The retrieved SWHs can be used for correcting the sea state bias of InIRA-derived sea surface heights and can supplement SWH products from other spaceborne sensors. First, we analyzed tilt, range bunching and velocity bunching wave modulations at low incidence angles, and we found clear dependencies between the SWH and two defined factors, range and azimuth integration, for ocean waves in the range and azimuth directions, respectively. These dependencies were further confirmed using InIRA measurements and collocated WaveWatch III (WW3) data. Then, an empirical orthogonal SWH model using the range and azimuth integration factors as model inputs was proposed. The model was segmented by the incidence angle, and the model coefficients were estimated by fitting the collocation at each incidence angle bin. Finally, the SWHs were retrieved from InIRA data using the proposed model. The retrievals were validated using both WW3 and altimeter (JASON2, JASON3, SARAL, and HY2A) SWHs. The validation with WW3 data shows a root mean square error (RMSE) of 0.43 m, while the average RMSE with all traditional altimeter data is 0.48 m. This indicates that the InIRA can be used to measure SWHs. |
| first_indexed | 2024-03-10T10:15:11Z |
| format | Article |
| id | doaj.art-fdc5b185edbe4103ac306521012b9a07 |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-10T10:15:11Z |
| publishDate | 2021-06-01 |
| publisher | MDPI AG |
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| series | Remote Sensing |
| spelling | doaj.art-fdc5b185edbe4103ac306521012b9a072023-11-22T00:55:58ZengMDPI AGRemote Sensing2072-42922021-06-011312241310.3390/rs13122413Preliminary Significant Wave Height Retrieval from Interferometric Imaging Radar Altimeter Aboard the Chinese Tiangong-2 Space LaboratoryLin Ren0Jingsong Yang1Xiao Dong2Yongjun Jia3Yunhua Zhang4State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, ChinaState Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, ChinaNational Space Science Center, Chinese Academy of Sciences, Beijing 100190, ChinaNational Satellite Ocean Application Service, Ministry of Natural Resources, Beijing 100081, ChinaNational Space Science Center, Chinese Academy of Sciences, Beijing 100190, ChinaThe interferometric imaging radar altimeter (InIRA) aboard the Chinese Tiangong-2 space laboratory is the first spaceborne imaging radar working at low incidence angles. This study focuses on the retrieval of significant wave heights (SWHs) from InIRA data. The retrieved SWHs can be used for correcting the sea state bias of InIRA-derived sea surface heights and can supplement SWH products from other spaceborne sensors. First, we analyzed tilt, range bunching and velocity bunching wave modulations at low incidence angles, and we found clear dependencies between the SWH and two defined factors, range and azimuth integration, for ocean waves in the range and azimuth directions, respectively. These dependencies were further confirmed using InIRA measurements and collocated WaveWatch III (WW3) data. Then, an empirical orthogonal SWH model using the range and azimuth integration factors as model inputs was proposed. The model was segmented by the incidence angle, and the model coefficients were estimated by fitting the collocation at each incidence angle bin. Finally, the SWHs were retrieved from InIRA data using the proposed model. The retrievals were validated using both WW3 and altimeter (JASON2, JASON3, SARAL, and HY2A) SWHs. The validation with WW3 data shows a root mean square error (RMSE) of 0.43 m, while the average RMSE with all traditional altimeter data is 0.48 m. This indicates that the InIRA can be used to measure SWHs.https://www.mdpi.com/2072-4292/13/12/2413Tiangong-2 space laboratoryinterferometric imaging radar altimeter (InIRA)significant wave height (SWH)empirical modelretrieval |
| spellingShingle | Lin Ren Jingsong Yang Xiao Dong Yongjun Jia Yunhua Zhang Preliminary Significant Wave Height Retrieval from Interferometric Imaging Radar Altimeter Aboard the Chinese Tiangong-2 Space Laboratory Remote Sensing Tiangong-2 space laboratory interferometric imaging radar altimeter (InIRA) significant wave height (SWH) empirical model retrieval |
| title | Preliminary Significant Wave Height Retrieval from Interferometric Imaging Radar Altimeter Aboard the Chinese Tiangong-2 Space Laboratory |
| title_full | Preliminary Significant Wave Height Retrieval from Interferometric Imaging Radar Altimeter Aboard the Chinese Tiangong-2 Space Laboratory |
| title_fullStr | Preliminary Significant Wave Height Retrieval from Interferometric Imaging Radar Altimeter Aboard the Chinese Tiangong-2 Space Laboratory |
| title_full_unstemmed | Preliminary Significant Wave Height Retrieval from Interferometric Imaging Radar Altimeter Aboard the Chinese Tiangong-2 Space Laboratory |
| title_short | Preliminary Significant Wave Height Retrieval from Interferometric Imaging Radar Altimeter Aboard the Chinese Tiangong-2 Space Laboratory |
| title_sort | preliminary significant wave height retrieval from interferometric imaging radar altimeter aboard the chinese tiangong 2 space laboratory |
| topic | Tiangong-2 space laboratory interferometric imaging radar altimeter (InIRA) significant wave height (SWH) empirical model retrieval |
| url | https://www.mdpi.com/2072-4292/13/12/2413 |
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