A local positive feedback of the tropical Pacific ocean-atmosphere system on interdecadal timescales

Interdecadal variability characteristics of ocean-atmosphere interaction in the tropical areas are investigated by using atmospheric reanalysis data and oceanic dataset. Results indicate that due to the ocean-atmosphere system’s internal adjustment on interdecadal time scales, the exchanges of latent heat and sensible heat between the ocean and at- mosphere are reduced by means of weakening trade wind, causing oceanic thermocline anomalies and resulting in unusual warming of sea surface tem- perature in the central and eastern Pacific. Mean- while the increases of sea surface temperature fa- cilitate much more development of convection in the eastern Pacific and excite a local ascending motion in the eastern and anomalous westerlies in the central and eastern Pacific, which further weaken the Walker circulation, and vice versa. Thus these processes constitute an interdecadal mode of positive feedback. This interdecadal feedback of the tropical ocean- atmosphere system is different from the previous conclusion of a so-called midlatitude-driving mecha- nism, which was used to explain the decadal vari- ability in the tropical Pacific Ocean.