Indian Ocean Crossing Swells: New Insights from “Fireworks” Perspective Using Envisat Advanced Synthetic Aperture Radar

He Wang,Romain Husson,Bertrand Chapron,Alexis Mouche

doi:10.3390/rs13040670

Abstract

Synthetic Aperture Radar (SAR) in wave mode is a powerful sensor for monitoring the swells propagating across ocean basins. Here, we investigate crossing swells in the Indian Ocean using 10-years Envisat SAR wave mode archive spanning from December 2003 to April 2012. Taking the benefit of the unique “fireworks” analysis on SAR observations, we reconstruct the origins and propagating routes that are associated with crossing swell pools in the Indian Ocean. Besides, three different crossing swell mechanisms are discriminated from space by the comparative analysis between results from “fireworks” and original SAR data: (1) in the mid-ocean basin of the Indian Ocean, two remote southern swells form the crossing swell; (2) wave-current interaction; and, (3) co-existence of remote Southern swell and shamal swell contribute to the crossing swells in the Agulhas Current region and the Arabian Sea.

Highlights

Envisat Advanced Synthetic ApertureIt is estimated that more than 75% waves across the world seas are generated by remote storms that propagate as long-period ocean waves or swells [1]
7b) using areas, ASAR i.e., WMthe in present the three crossing-swell dominated mid-Indian. Ocean basin, the this case, Sea, the complex crossing swell state resulted from the co-existence of Southern Ocean
The discrimination of crossing swell mechanisms could be revealed by comparative analysis taking opportunity of the Synthetic Aperture Radar (SAR) Wave Mode (WM) fireworks technique

Summary

Introduction

It is estimated that more than 75% waves across the world seas are generated by remote storms that propagate as long-period ocean waves or swells [1]. Crossing swells [2], defined as complex sea state of at least two swell systems with different directions, are of importance in navigation safety. Radar (SAR), equipped with the specific Wave Mode (WM), is the only spaceborne sensor that is able to provide the directional ocean wave spectra on a global scale in the long term [4,5]. In contrast to altimeters only providing wave height without directional information, wave spectra from SAR WM could readily distinguish swell from local wind sea and even separate different swell systems.

Objectives

Findings

Discussion

Conclusion