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<p>In this study, Beta geophysical products over both land and oceans from the recently launched surface water and ocean topography mission (SWOT) are evaluated using in-situ and other altimeter data over the Indian region during its calibration and validation phase (March 29, 2023, to July 10, 2023). For hydrological applications, pseudo water surface digital elevation maps (DEMs) were prepared for a stretch of the Narmada River and its tributary, as well as for a few reservoirs and floodplain wetlands in India. Nadir altimetry retrieved water levels over the Narmada River were found in good agreement with ground observations with RMSE of the order of 42 cm. Although, in most of the cases the swath altimetry derived water surface elevation (WSE) were in sync with in situ observations, but in a&#xa0;few cases erroneous values were also observed with a standard deviation of the order of 1.5&#xa0;m. One notable finding from the study is the estimation of the slope along the observed stretch, with a value of 20 cm/km in the Narmada River and 48 cm/km in its tributary, the River Tawa. Initial results from swath altimetry measurements have added a new dimension to the field of land hydrology and are essential for understanding hydrological processes and water resource management. Over the oceans, the sea level anomaly from SWOT swath data is compared with in-situ measurements and available nadir altimeter data. For the limited period from March 29, 2023, to July 10, 2023, the root mean square deviation (RMSD) of SWOT-derived sea level anomaly in comparison to coastal tide gauges and the directional wave and tide recorder (DWTR) is found to be 5.8–7.7 cm, while it is 3.2 cm and 3.5 cm compared to Sentinel-6A and AVISO-L4, respectively, over the open ocean. The power spectrum of sea level reveals that SWOT’s swath data can resolve smaller scales (4–100 km) compared to the AVISO-L4 sea levels.</p>

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Evaluation of SWOT Beta Geophysical Products in the Indian Region During CAL-VAL Phase over the Land and Oceans

  • 期刊论文

  • 发表日期：

    2025年6月18日

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  • Aditya Chaudhary,
  • Shard Chander,
  • Arun Kumar Surisetty,
  • Ritesh Agrawal,
  • Neeraj Agarwal,
  • Praveen Kumar Gupta,
  • Raj Kumar,
  • Rashmi Sharma,
  • R. Venkat Shesu,
  • T. V. S. Udaya Bhaskar,
  • E. Pattabhi Rama Rao

摘要

In this study, Beta geophysical products over both land and oceans from the recently launched surface water and ocean topography mission (SWOT) are evaluated using in-situ and other altimeter data over the Indian region during its calibration and validation phase (March 29, 2023, to July 10, 2023). For hydrological applications, pseudo water surface digital elevation maps (DEMs) were prepared for a stretch of the Narmada River and its tributary, as well as for a few reservoirs and floodplain wetlands in India. Nadir altimetry retrieved water levels over the Narmada River were found in good agreement with ground observations with RMSE of the order of 42 cm. Although, in most of the cases the swath altimetry derived water surface elevation (WSE) were in sync with in situ observations, but in a few cases erroneous values were also observed with a standard deviation of the order of 1.5 m. One notable finding from the study is the estimation of the slope along the observed stretch, with a value of 20 cm/km in the Narmada River and 48 cm/km in its tributary, the River Tawa. Initial results from swath altimetry measurements have added a new dimension to the field of land hydrology and are essential for understanding hydrological processes and water resource management. Over the oceans, the sea level anomaly from SWOT swath data is compared with in-situ measurements and available nadir altimeter data. For the limited period from March 29, 2023, to July 10, 2023, the root mean square deviation (RMSD) of SWOT-derived sea level anomaly in comparison to coastal tide gauges and the directional wave and tide recorder (DWTR) is found to be 5.8–7.7 cm, while it is 3.2 cm and 3.5 cm compared to Sentinel-6A and AVISO-L4, respectively, over the open ocean. The power spectrum of sea level reveals that SWOT’s swath data can resolve smaller scales (4–100 km) compared to the AVISO-L4 sea levels.