Firstly, a negative signal appears and develops at the model Kuroshio extension region around 40｡?. Then it moves southwestward in the central North Pacific to the latitude around 20｡?. Afterwards it extends to the subtropical western Pacific region.
The VAT variation of this mode is closely linked to the midlatitude SST variation. SST anomaly is large between 30｡? and 40｡?. Development of a negative SST signal aroud the Kuroshio extension is accompanied by stronger westerly surface wind (stronger cold Ekman current and negative heat flux into the ocean) than normal over that region. The region where the trade winds are weaker than normal corresponds to the region of positive SST anomaly in the subtropical eastern Pacific (Fig. 8). In the tropical eastern Pacific, the SST anomaly shows asymmetric pattern about the equator. The wind stress anomaly shows intensified subtropical anti-cyclonic circulation and midlatitude westerly, and trade winds stronger than normal in the northern hemisphere and weaker than normanl in the southern hemisphere. These features of the SST and surface wind are reminiscent of wind-SST feedback mechanism for the decadal dipole oscillations in the Atlantic Ocean which is proposed by Xie and Tanimoto (1998).
The temperature variation in the vertical-meridional cross section (Fig. 9) reveals that a temperature anomaly at the midlatitude surface moves down and southware into the subthward into the subtropical subsurface deeper than 200m along the isopycnal surfaces at around 25.5s. This vertical structure is consistent with that of the observed subduction (Deser et al., 1996). When the positive temperature anomaly subduted into the subsruface srbtropical region, a positive wind stress curl anomaly is dominant over the subtropical central North Pacific (150｡?-170｡?, 20｡?-30｡?). It is suggested that variation of wind stress curl in the subtropical North Pacific reinforces the subsurface signals in the western Pacific through the Ekman pumping and spin-up (spin-down) the subtropical gyre.
