Horizontal and vertical energy fluxes of ocean surface waves and their derivation from spaceborne altimeter measurements

TL;DR

This paper presents a satellite-based method to accurately estimate both vertical and horizontal energy fluxes of ocean surface waves, enhancing understanding of air-sea energy exchange and ocean energy budgets globally.

Contribution

It introduces an algorithm to derive wave period from satellite data and validates energy flux estimates against buoy measurements across diverse climates.

Findings

Vertical energy flux follows cubic wind speed dependence.

Horizontal energy flux is less dependent on wind speed, dominated by long swell.

Satellite estimates agree well with buoy measurements across different regions.

Abstract

Recent research shows that the surface wave energy dissipation, which is the vertical energy flux across the air-sea interface, can be calculated as the product of air density, reference wind speed cubed and an energy transfer coefficient determined by the dimensionless parameters made of wind speed, significant wave height and dominant wave period. In a similar way, the horizontal wave energy flux of wind generated waves can be represented by the same dimensionless wind and wave parameters. Satellite altimeters routinely report reference wind speed and significant wave height. An algorithm to derive the characteristic wave period of ocean waves in the altimeter footprint using the similarity properties of ocean wind and waves is described. The vertical and horizontal energy fluxes derived from the satellite altimeter are in very good agreement with the estimation from ocean buoy measurements in four geography locations with significantly different wind and wave climates. The vertical energy flux follows closely the cubic wind speed dependence, reflecting the dominance of short wave contribution in wave generation and breaking dissipation. The wind speed dependence of horizontal energy flux is much weaker especially in mild to moderate wind speed, reflecting its dominance by long swell component. Application of the energy flux parameterization functions to satellite altimeter measurements offers an efficient method of estimating the air-sea exchange and ocean energy budget in global scale. Such data are extremely difficult to acquire using other means.