Improvement of SSA Approach for Numerical Simulation of Sea Surface Scattering at High Microwave Bands

Peng-Bo Wei,Ding Nie,Min Zhang,Yong-Chang Jiao

doi:10.3390/rs10071021

Abstract

Small slope approximation (SSA) is a widely accepted approach in sea surface electromagnetic (EM) scattering studies. Nevertheless, the spatial sample interval used for sea surface should be around or even smaller than one-eighth of the incident wavelength to ensure EM scattering calculation accuracy, which requires a huge amount of computation, creating an obstacle to scattering numerical simulation, especially for high microwave band incident waves and large sea surface scenes. In this paper, a novel realization approach for SSA is proposed to significantly decrease the computation demands and computer memory requirements in sea surface scattering simulation. First, the sea surface is decomposed into two scales, and each scale has its own spatial sample interval. Then, the inclination state of the large-scale sea surface is determined under a specific wind speed. After that, scattering calculations of a typical surface cell with a finely sampled structure are completed and saved in all possible situations. Finally, scattering results for all the cells of a concrete sea surface are extracted from the saved cell scattering data base. From the different kinds of scattering result comparisons, it is demonstrated that this novel SSA realization approach can attain almost similar scattering results to exact SSA. This approach can be broadly applied in composite scattering studies, and remote sense imaging simulation of large sea surfaces with multiple targets.

Highlights

The ocean is playing an increasingly important role in politics, economy, culture, and other areas worldwide
As small slope approximation (SSA) avoids the empirically scale partition in the two-scale model (TSM) model, is more accurate, and has larger application scope, it has been widely applied to the practical rough surface scattering problems, and especially in sea surface scattering studies, where SSA has been proven to be reliable compared with the other methods and experiment data [14,15,16,17]
The SSA method has been developed into a deterministic model, which is favorable for some other application areas, such as composite scattering problems for rough surfaces with targets [18], synthetic aperture radar (SAR) image simulation of maritime scenes, and dynamic scattering of the sea surface [19,20]

Summary

Introduction

The ocean is playing an increasingly important role in politics, economy, culture, and other areas worldwide. Theoretically approximate approaches [9,10], like the Kirchhoff approximation (KA) method, small perturbation method (SPM), two-scale model (TSM), and small slope approximation (SSA) [11], usually accomplish the calculation with their corresponding assumptions, with which the original problems can be greatly simplified, resulting in a considerable decrease in computation demand. Armed with these approaches, EM scattering of two-dimensional (2D) surfaces and some other practical problems can be solved efficiently with precise or acceptable results.

Proposed Method

Sea Surface Decomposition and Synthesis

Numerical Simulations and Discussion

Conclusions