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Measurements of Waves in a Wind-wave Tank Under Steady and Time-varying Wind Forcing
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A Preliminary Analysis of Wind Retrieval, Based on GF-3 Wave Mode Data
Lei Wang1,2,3, Bing Han4,5, Xinzhe Yuan6
1Key Laboratory of Technology in Geo-Spatial Information Processing and Application Systems, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China. wanglei162@mails.ucas.edu.cn.
Sensors (Basel, Switzerland)
|May 19, 2018
Summary
This study validates normalized calibration for China's Gaofen-3 (GF-3) synthetic aperture radar (SAR) using ocean wind data. It confirms GF-3 SAR can accurately measure wind fields and polarization characteristics.
Area of Science:
- Earth Observation
- Remote Sensing
- Oceanography
Background:
- Accurate calibration of synthetic aperture radar (SAR) data is crucial for quantitative geophysical measurements.
- The Gaofen-3 (GF-3) satellite provides valuable C-band SAR data, but its calibration requires validation.
- Understanding the relationship between normalized radar cross-section (NRCS) and ocean surface wind conditions is essential for remote sensing applications.
Purpose of the Study:
- To validate the feasibility of using ocean surface wind fields and VV-polarized NRCS for normalized calibration of the GF-3 SAR Wave Mode.
- To investigate the relationship between cross-polarization NRCS and wind vectors.
- To analyze the properties of the polarization ratio (PR) and develop empirical models for it.
Main Methods:
- Analysis of 2779 GF-3 quad-polarization SAR images in Wave Mode collocated with ERA-Interim wind vectors.
- Utilizing the C-band geophysical model function (CMOD4) to estimate calibration constants.
- Developing empirical models for polarization ratio (PR) based on incidence and azimuth angles.
Main Results:
- Feasibility of normalized calibration using VV-polarized NRCS and wind fields is verified.
- Cross-polarization NRCS shows a linear increase with wind speed, modulated by wind direction above 8 m/s.
- Developed PR models, dependent on incidence and azimuth angles, improve retrieval accuracy.
Conclusions:
- The GF-3 SAR Wave Mode data can be reliably used for normalized calibration.
- The study provides insights into the behavior of cross-polarization NRCS and polarization ratio for C-band SAR.
- The developed PR models enhance the accuracy of retrieved NRCS (σ VV 0 and σ HH 0).
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