Acoustic-gravity waves in the atmosphere generated by infragravity waves in the ocean

Terence W Bullett,Oleg A Godin,Nikolay A Zabotin

doi:10.1186/s40623-015-0212-4

Abstract

Abstract Infragravity waves are surface gravity waves in the ocean with periods longer than approximately 30 s. Infragravity waves propagate transoceanic distances and, because of their long wavelengths, provide a mechanism for coupling wave processes in the ocean, atmosphere, and the solid Earth. Here, we present a strict physical justification for the hypothesis that background ocean waves may generate waves in the upper atmosphere. We show that, at frequencies below a certain transition frequency of about 3 mHz, infragravity waves continuously radiate their energy into the upper atmosphere in the form of acoustic-gravity waves. Based on ionospheric observations and estimates of the fluxes of the mechanical energy and momentum from the deep ocean, we conclude that acoustic-gravity waves of oceanic origin may have an observable impact on the upper atmosphere. We anticipate our work to be a starting point for a detailed analysis of global manifestations of the ocean-generated background acoustic-gravity waves.

Highlights

Infragravity waves are surface gravity waves in the ocean with periods longer than approximately 30 s
Using a coupled atmosphere-ocean model taking into account both compressibility of the air and the gravity, we show that there exist two distinct regimes of infragravity wave (IGW) penetration into the atmosphere
At frequencies below the transition frequency, IGWs continuously radiate their energy into the upper atmosphere in the form of acoustic-gravity waves (AGWs)

Summary

Introduction

Infragravity waves are surface gravity waves in the ocean with periods longer than approximately 30 s. Infragravity waves propagate transoceanic distances and, because of their long wavelengths, provide a mechanism for coupling wave processes in the ocean, atmosphere, and the solid Earth. We present a strict physical justification for the hypothesis that background ocean waves may generate waves in the upper atmosphere. At frequencies below a certain transition frequency of about 3 mHz, infragravity waves continuously radiate their energy into the upper atmosphere in the form of acoustic-gravity waves. Based on ionospheric observations and estimates of the fluxes of the mechanical energy and momentum from the deep ocean, we conclude that acoustic-gravity waves of oceanic origin may have an observable impact on the upper atmosphere. We anticipate our work to be a starting point for a detailed analysis of global manifestations of the ocean-generated background acoustic-gravity waves

Methods

Results

Conclusion