Scales and non-dimensional numbers characterizing ocean turbulence and their practical application for estimating eddy diffusivities

Abstract

The strength of the vertical eddy diffusivity determines the structure of oceanʼs general circulation, which affects the climate change. Therefore, global estimation of vertical eddy diffusivity is required; however, focusing on the direct observation of turbulence (dissipation rates) for estimation within limited ship time is difficult. Even if observations are made, understanding factors such as wind, tide, internal wave breaking, and sea surface cooling, which are energy sources of turbulence, and parameters characterizing the turbulence is crucial. In this review, the length scales ranging from a few millimeters to several tens of meters and dimensionless numbers used in ocean turbulence analysis are summarized to promote the understanding of the turbulence; particularly, we focus on practical estimation methods for dissipation rates to accelerate research using observed turbulence data.