The above image is taken from "Atmosphere–Ocean Momentum Exchange in General Circulation Models", John A.T.Bye 1999. It represents the inertial coupling concept between the atmosphere and ocean.
It is a concept which helps to model momentum transfer between the atmosphere and ocean, taking into account gravity waves on the surface of the ocean. This diagram is used to help illustrate the formulation of shear stress vectors for both the atmosphere and ocean.
The only problem I have is I do not know what is meant by reference velocity? Supposedly this velocity is shared between both mediums, atmosphere and ocean.
What could this refer to?
Any help at all would be appreciated.