The short frequency currents are calculted by subrtacting the low-pass field from the detided field. The surface divergence is calculated based on the low-pass current field. It is a measure of if water motion toward or away from a particular point on the ocean surface. Positive values represent water being forced away and negative values represent water forced toward the surface point. The following surface vorticity plot is calculated based on the low-pass current field.
Counterclockwise rotation is positive and clockwise rotation is negative.