The square root of one value of this quantity divided by the beta-plane parameter gives the Rhines scale. In some non-dimensionalization problems, it's good to know that the units of geopotential are the square of this quantity's units. The ratio of the pressure gradient to the density equals the Coriolis parameter times a component of this quantity for a system in geostrophic balance. Derivatives of a function denoted psi give this quantity's (*) zonal and meridional components. As depth increases, this quantity's direction twists away from the direction of a shearing wind, forming an Ekman spiral. (-5[1])This quantity multiplies cross-sectional area to give volumetric flow rate, (10[1])and its curl is the vorticity. For 10 points, name this quantity, which for large currents like the Gulf Stream can reach values of 2.5 meters per second. ■END■ (10[1])