Interannual variability in the eastern subtropical Pacific Ocean.

摘要

Interannual variability in the eastern subtropical Pacific Ocean is investigated using the Naval Research Laboratory Layered Ocean Model (NLOM). Emphasis is placed on examining the nature of westward propagating Rossby waves and their interaction with the overlying atmosphere.; Singular value decomposition (SVD), complex empirical orthogonal function (CEOF) and multivariate singular spectrum (M-SSA) analyses are used to isolate the standing and propagating response due to Rossby waves and wind stress curl (WSC) anomalies as well as their dominant frequencies of oscillation respectively. In addition to a large scale interdecadal fluctuation, two distinct forms of Rossby waves are found to exist.; SVD and CEOF analyses suggest a leading order source of variability stemming from a large scale interdecadal fluctuation. M-SSA analysis also depicts this low frequency mode, but to a lesser extent and at higher order. The modeled temporal coverage limits the extent to which this feature can be studied further.; Of primary interest in the eastern subtropical Pacific Ocean are large scale interannual wind forced Rossby wave variations. Independent M-SSA analysis of upper layer thickness (ULT) and WSC anomalies suggests a low frequency (∼51 month period) atmospherically forced ocean response in which westward atmospheric propagation leads forced oceanic Rossby wave propagation by roughly 3 months.; In addition to this low frequency forced oceanic wave response, a distinct freely propagating biennial (∼24 month period) oceanic Rossby wave is found to exist. Longitude lag/time lag correlation matrices reveal phase speeds c_τ ∼ 8 cm/ s and c_τ ∼ 12 cm/ s for the freely propagating and forced Rossby waves respectively, both in accordance with their respective theories.; Model results and forcing are compared with TOPEX/POSEIDON altimetry and Florida State University pseudo-stresses respectively. The model compares extremely well with independent observations giving validity to the results and choice of forcing while providing substantive evidence for the ability of the ocean model to reproduce oceanic variability.