An observational study of the impact of the North Pacific SST on the atmosphere

To investigate the observed atmospheric response to SST variability in the North Pacific, the Maximum Covariance Analysis is performed between the monthly sea surface temperature anomaly ( SSTA) and the 500- hPa geopotential height anomaly over the North Pacific using observations of the period 1958 - 1993. In addition to the strong remote ENSO impact in winter months, the MCA analysis suggests a significant local atmospheric response, with the summer atmosphere corresponding to the preceding winter SST over the North Pacific. In this local response, a horseshoe SSTA in winter, with a positive SSTA loading over the central- western North Pacific surrounded by a negative SSTA, appears to persist into the spring and summer, eventually leading to an atmospheric response in summer with a wave- train over the mid- latitude North Pacific. This local response may imply some predictability of the North Pacific summer atmospheric circulation with a lead time of up to 6 months.