Estimating Energy Dissipation Rate from Breaking Waves Using Polarimetric SAR Images

Area of Science:

• Oceanography
• Remote Sensing
• Atmospheric Science

Background:

• The total energy dissipation rate (ϵt) is crucial for understanding ocean-atmosphere energy exchange.
• Traditional methods for estimating ϵt are limited in spatial and temporal coverage.
• Satellite remote sensing offers a synoptic scale approach for estimating wave breaking parameters.

Purpose of the Study:

• To utilize polarimetric Synthetic Aperture Radar (SAR) data for estimating the total energy dissipation rate (ϵt) on the ocean surface.
• To assess the accuracy of SAR-derived ϵt under various wind and sea conditions.
• To improve climate and wave models by providing reliable ϵt estimations.

Main Methods:

• Decomposition of SAR backscatter into polarized (Bragg) and non-polarized (Non-Bragg) contributions.
• Estimation of wind and wave parameters from the Non-Bragg contribution.
• Calculation of ϵt using a parametric model dependent on estimated wind and wave parameters.

Main Results:

• SAR-derived ϵt showed good agreement with numerical simulations for wind seas.
• Higher than expected ϵt was observed under prevailing swell conditions.
• The methodology proved satisfactory for light to moderate wind conditions (below 10 m s-1).

Conclusions:

• Polarimetric SAR data is a viable tool for estimating ocean surface energy dissipation.
• The developed methodology enhances the capability of SAR for ϵt estimation, particularly in previously challenging conditions.
• Accurate ϵt data can significantly improve climate and wave model performance.