Since 2018, for the first time, space measurements of colocated wind vectors and wave spectral characteristics are available thanks to the French/Chinese CFOSAT mission, which carries a wind scatterometer (SCAT) and a wave scatterometer (SWIM). Four years after its launch, CFOSAT data processing has been improved to reach a high level quality, leading to a reprocessing of the whole mission dataset. This paper focuses on the CFOSAT SWIM data reprocessing, the product performance, now homogeneous over mission lifetime, the complementarity with SAR observations and some scientific contributions to oceanography.

The availability of wide swath Significant wave heights (SWH) such as those retrieved in the frame of CFOSAT and HY2B satellite missions opens important perspectives for the improvement of operational wave forecasting. The objective of this work is to analyze the impact of the combined assimilation of wide swath SWH and directional wave spectra on the integrated wave parameters in the analysis and forecast periods. The results show a significant improvement of the SWH estimate in different ocean regions. We clearly showed the persistency of the assimilation up to 3 days in the forecast period. Most striking is the ability of the combined assimilation to effectively correct swell tracking for storm events, such as Hurricane Pablo in 2019.

For the first time, co-located wind vectors and wave spectral characteristics are available thanks to the French/Chinese CFOSAT mission, which includes a wind scatterometer SCAT and a wave scatterometer SWIM. Three years after its launch, CFOSAT data is thoroughly qualified and various scientific work has been undertaken. This paper focuses on CFOSAT SWIM data, its performance and scientific contribution to oceanography, coastal and sea ice study.

The CFOSAT (China France Oceanography Satellite) mission launched in 2018 now routinely provides at the global scale, directional spectra of ocean waves. The principle is based on the analysis of the normalized radar cross-section measured by the instrument SWIM (Surface Waves Investigation and Monitoring), a near-nadir pointing Ku-Band real-aperture scanning radar. From the ocean wave spectra derived from SWIM, the principal parameters of ocean wave spectra as significant wave height, peak wavelength, and peak direction are now available to better characterize the sea-state. However, it is known that these principal parameters are not sufficient not fully characterize the distribution of wave energy and understand or validate the physical processes impacting its evolution during growth order decay. Here we show that the parameters characterizing the shape of the wave spectra (e.g directional and frequency spread) can be estimated at the global scale from the SWIM measurements. We also show that they can provide consistent values of the Benjamin-Feir index, an index proposed to estimate the probability of extreme waves. Similarities of differences with the shape parameters of the MFWAM numerical wave model are also discussed.

The Chinese-French oceanography satellite, CFOSAT, was launched on October 2018. Two Ku-band scatterometers are on-board: SCAT for the wind observation and SWIM for the wave observation. After a first phase mainly dedicated to validation and identification of improvement possibilities, the ground processing and products generated were upgraded. This paper presents the main evolutions implemented and their positive impacts on the SWIM data quality.

This article describes the first results obtained from the Surface Waves Investigation and Monitoring (SWIM) instrument carried by the China France Oceanography Satellite (CFOSAT), which was launched on October 29, 2018. SWIM is a Ku-band radar with a near-nadir scanning beam geometry. It was designed to measure the spectral properties of surface ocean waves. First, the good behavior of the instrument is illustrated. It is then shown that the nadir products (significant wave height, normalized radar cross section, and wind speed) exhibit an accuracy similar to standard altimeter missions, thanks to a new retracking algorithm, which compensates a lower sampling rate compared to standard altimetry missions. The off-nadir beam observations are analyzed in detail. The normalized radar cross section varies with incidence and wind speed as expected from previous studies presented in the literature. We illustrate that, in order to retrieve the wave spectra from the radar backscattering fluctuations, it is crucial to apply a speckle correction derived from the observations. Directional spectra of ocean waves and their mean parameters are then compared to wave model data at the global scale and to in situ data from a selection of case studies. The good efficiency of SWIM to provide the spectral properties of ocean waves in the wavelength range [70-500 m] is illustrated. The main limitations are discussed, and the perspectives to improve the data quality are presented.

The Chinese-French oceanography satellite, CFOSAT, was launched on October 2018. Two Ku-band scatterometers are on-board: SCAT for the wind observation and SWIM for the wave observation. This paper presents the most recent results on the SWIM data quality analysis a few months after the end of the CAL/VAL phase.

The China-France Oceangraphy SATellite (CFOSAT) is an innovative satellite mission with wind and waves measurements on oceans. This paper aims to evaluate the first results of the assimilation of the wave data provided by CFOSAT in the wave model MFWAM. Model runs are implemented during the Calibration/Validation phase of the mission. The results are compared to the wave data from altimeters and buoys. The first results are promising and indicate a significant improvement of wave heights in the different ocean basins (high latitudes, intermediate latitudes and the tropics). Azimuthal cut-off sensitivity tests for the SWIM wave spectra are also examined in this study. We also discussed the impact of combined wave spectra and the ones from the incidence angles of SWIM (6, 8 and 10°). In other respects this study also investigate the complementary use of SWIM and SAR from CFOSAT and SAR from Sentinel-1 for combined assimilation in the wave model MFWAM

This paper presents the goal, organization and first results of the calibration and validation activities devoted to the Ku-band wave scatterometer SWIM in operation since the end of October 2018 after the launch of the China-France Oceanography SATellite CFOSAT.

The increasing number of directional wave spectra from satellites is a very important opportunity for the improvement of operational wave forecast. This will lead to a better understanding of swell dissipation which is still a top task in wave modeling. This work aims to investigate how the assimilation of different sources of directional wave spectra will impact the analysis and forecast of wave parameters. Two satellites, sentinel-1A and 1B, provide the level 2 SAR wave spectra, which have been qualified for operational use regarding to the calibration/validation phase developed in the last two years. This year the launch of the satellite CFOSAT will ensure a third source directional wave spectra from the real aperture radar SWIM and a significant wave height at nadir look. Synthetic wave data of SWIM and wave spectra from S1A and S1B are assimilated conjointly in the wave model MFWAM for 1 cycle of 13 days during the southern winter season. Two sets of synthetic SWIM data with and without instrumental errors have been tested in the assimilation. The validation of the results with altimeters significant wave heights shows a significant impact in the periods of analysis and forecast. In this study we also investigated the impact of instrumental errors provided by SWIM simulator and the wavelength cut-off on the assimilation results.

This paper is on the retrieval of spectral properties of surface ocean waves from the real-aperture radar KuROS carried on an airplane. The system was designed to prepare the satellite mission CFOSAT and to contribute to its validation. In addition, KuROS provides Doppler measurements which are analyzed as Doppler velocity spectra co-located with the wave height spectra derived from intensity measurements. Data have been acquired from 2013 to 2017 in various circumstances including fetch-limited, swell, or mixed sea conditions and under moderate to high wind conditions. In this paper we present results on the directional spectra obtained and on the associated integral parameters such as significant wave height, peak direction, peak wavelength (or frequency), directional and frequency spreads. Comparisons with outputs of the wave model hindcast (MFWAM model) are presented. We also show some results on the Doppler fluctuation spectra.

With a low cut-off for the directional wave spectra CFOSAT will impact both mixed sea and swell. The complementary use of CFOSAT and SAR wave spectra will enhance the impact of the assimilation and therefore induce a more accurate sea state. The CFOSAT mission is on one hand a big challenge for operational wave forecasting system, and on the other hand a good opportunity for wave modellers in order to improve the source and dissipation terms in the wave model.

The Chinese and French Space Agencies are jointly preparing an innovative mission, CFOSAT (China France Oceanography Satellite) devoted to the monitoring of the ocean surface and its related science and applications. This paper gives an overview of the scientific objectives, the mission and instrument characteristics, the expected data products and their performance.

In order to improve the wave forecast, the assimilation of directional wave spectra in wave model has been developed at Meteo France. The assimilation scheme is tested for real ENVISAT ASAR wave spectra provided by the European Space Agency. The scheme takes into account the limitation in frequency related to the ASAR instrument. The preliminary results show that the assimilation of wave spectra is efficient and works correctly. The impact of the assimilation on wave parameters is significant and stays effective in the forecast period. In addition, statistical analysis has shown good skill in term of root mean square and assimilation index for the analyzed wave parameters (wave height, direction and frequency).