Abstract
Effect of friction on the geostrophic flow was examined theoretically and numerically. It is shown that by the effect of vertical eddy viscosity the velocity of geostrophic current will be as a rule strengthened in magnitude and the actual current pattern will not be approximated by geostrophic current unless we add to it the pure drift current of EKMAN'S type corresponding to the prevailing winds blowing over the sea surface. It is concluded that the error due to the effect of eddy viscosity is equal to or exceeds the error resulting in from the uncertainty in choosing the reference layer in dynamic computation of ocean currents.
