Stokes drift in equatorial water waves, and wave–current interactions

In this paper we review recent developments which enable the mathematical determination of various drift properties induced by water waves, and wave–current interactions, in the equatorial region. In particular, we describe results pertaining to a recently constructed exact solution of the geophysical fluid dynamic governing equations in the β− plane approximation at the Equator. The formulation of this exact solution renders it amenable to deriving an analytical expression for the Stokes' drift velocity, which is characterised in terms of the mean Eulerian flow velocity and the mean Lagrangian flow velocity. Additionally, an analysis of the associated mass transport is discussed. Notwithstanding the fact that the exact solution we discuss is in some sense a mathematical idealisation, from a physical perspective it may be regarded as a robust and reliable foundation on which to generate, and thereby model, more complex and intricate oceanographical flows.