Rationalized by the observational circulation pattern in the upper ocean of
the North Pacific, meridional friction term is first incorporated in a bar
otropic theoretical model of the wind-driven circulation. The governing pot
ential vorticity equation thence has beta term and wind stress curl term (t
he two of the Sverdrup balance), zonal friction term and meridional frictio
n term. The analytical solution satisfactorily captures many important feat
ures of the wind-driven circulation in the North Pacific: Kuroshio, Oyashio
, Kuroshio extension, North Equatorial Current, and especially the eastern
boundary currents in the North Pacific, i.e. California current and Alaska
current.