A joint method to retrieve directional ocean wave spectra from SAR and wave spectrometer data

• Published in: Chinese journal of oceanology and limnology Vol. 34; no. 4; pp. 847 - 858
• Main Author: 任林 杨劲松 郑罡 王隽
• Format: Journal Article
• Language: English
• Published: Heidelberg Science Press 01.07.2016; Springer Nature B.V
• Subjects: ASAR; Buoys; Data retrieval; Earth and Environmental Science; Earth Sciences; Information retrieval; Marine; Ocean waves; Oceanography; oceans; Parameters; Physics; SAR (radar); Sea state; Sea states; Sea surface; Sensitivity; Significant wave height; Spectra; spectrometers; Spectrum analysis; Storms; Synthetic aperture radar; water waves; Wave data; Wave direction; Wave height; Wave parameters; Wave spectra; Waveform analysis; wavelengths; Weather forecasting; 太阳能热水器; 数据反演; 方向性; 星载合成孔径雷达; 波谱仪; 海浪谱; 联合方法; wave spectrometer; joint method; directional ocean wave spectrum; Synthetic Aperture Radar (SAR)
• ISSN: 0254-4059; 2096-5508; 1993-5005; 2523-3521
• DOI: 10.1007/s00343-015-5043-4

This paper proposes a joint method to simultaneously retrieve wave spectra at dif ferent scales from spaceborne Synthetic Aperture Radar（SAR） and wave spectrometer data. The method combines the output from the two dif ferent sensors to overcome retrieval limitations that occur in some sea states. The wave spectrometer sensitivity coeffi cient is estimated using an ef fective signifi cant wave height（SWH）, which is an average of SAR-derived and wave spectrometer-derived SWH. This averaging extends the area of the sea surface sampled by the nadir beam of the wave spectrometer to improve the accuracy of the estimated sensitivity coeffi cient in inhomogeneous sea states. Wave spectra are then retrieved from SAR data using wave spectrometer-derived spectra as fi rst guess spectra to complement the short waves lost in SAR data retrieval. In addition, the problem of 180° ambiguity in retrieved spectra is overcome using SAR imaginary cross spectra. Simulated data were used to validate the joint method. The simulations demonstrated that retrieved wave parameters, including SWH, peak wave length（PWL）, and peak wave direction（PWD）, agree well with reference parameters. Collocated data from ENVISAT advanced SAR（ASAR）, the airborne wave spectrometer STORM, the PHAROS buoy, and the European Centre for Medium-Range Weather Forecasting（ECMWF） were then used to verify the proposed method. Wave parameters retrieved from STORM and two ASAR images were compared to buoy and ECMWF wave data. Most of the retrieved parameters were comparable to reference parameters. The results of this study show that the proposed joint retrieval method could be a valuable complement to traditional methods used to retrieve directional ocean wave spectra, particularly in inhomogeneous sea states.