Linkage between the Asian-Pacific Oscillation and the sea surface temperature in the North Pacific

Abstract

The linkage between the Asian-Pacific Oscillation (APO) and the sea surface temperature (SST) in the North Pacific during the summertime (June–August) is preliminarily investigated through an analysis of observed data. It is found that APO is significantly and positively correlated to the North Pacific SST, with the correlation coefficient being 0.58 on the interannual timescale during the period 1954–2003, which suggests that a strong (weak) APO corresponds to high (low) SST in the North Pacific. Their in-phase relationship is well supported by the dynamic and thermal conditions in association with the APO anomaly. When APO is in the positive phase, the East Asian westerly jet in the upper troposphere is weakened, and the anomalous anticyclonic circulation prevails in the low-troposphere over the North Pacific. Besides, the negative anomaly of the sensible and latent heat fluxes is predominated in the North Pacific, indicating ocean gets heat flux from the atmosphere. Meanwhile, warm water advection northward is strengthened in the North Pacific. All of these provide beneficial conditions to warm the North Pacific SST, and thus the SST is increased in this region, and vice versa.