276
Wind Stress Anomaly
0.1 0.2 0.3 0.4 0.5 0.6 0.8 0 .9
[0.01 Pal
1.1 1.2 1.3
Figure 5: Wind stress anomaly (Pa) used in the periodic forcing experiments with our
oeeM.
shown in Fig. 2b. It has been suggested by Palmer and Sun (1985) that
such a distribution of SST would result in a northward shift of the baroclinic eddy activity in the atmosphere, leading to a weakened Aleutian Low,
and subsequently reduced westerly winds over the mid-latitudes ocean. Indeed, the model results show that a reduced meridional SST gradient goes
along with anomalous high pressure over the entire North Pacific (Figs. 2b
and 2c).
To further investigate the nature of the atmospheric response to the
anomalous SST pattern, we forced the atmospheric component of our coupled model in a stand-alone integration by a SST pattern similar to that
shown in Fig. 2b. The integration was done in a perpetual January
mode and an ensemble of 12 January integrations was performed. The
atmospheric response is highly significant and shows the expected result:
anomalous high pressure over the North Pacific (Fig. 4a). We note, however, that the mean response becomes much weaker when the ensemble size