Relationship between real meridional volume transport and Sverdrup transport in the North Subtropical Pacific

摘要

The oceanic meridional volume transport (MVT) in the North Subtropical Pacific is calculated directly from an observed velocity field (real MVT) and indirectly from wind stress based on Sver-drup balance, respectively. It is confirmed that the Sverdrup MVT is a good approximation to the real MVT for the North Subtropical Pacific except in the western boundary region, where the difference is expected because of frictional and nonlinear effects. The time evolution of the MVT derived from a revised Sverdrup balance, in which a time delay due to the propagation of the first baroclinic Rossby wave is considered, is well correlated with that of the real MVT on decadal time scale, especially near the western boundary region. It is suggested that the Sverdrup balance can be used to study not only the mean climatology of the oceanic circulation, but also the time-dependent oceanic circulation of the North Subtropical Pacific when the Rossby wave propagation is taken into account.