THE TEMPORAL AND SPATIAL VARIATIONS IN AIR-SEA INTERACTION OVER THE PACIFIC OCEAN

Based on the monthly mean data of 1957-1976,the lag correlations between the monthly sea level pressure field over the North Pacific and the sea surface temperature (SST) averaged over the equatorial East Pacific region (5°N-5°S, 80°W-180), including the SST time-lagging by 6 months to time-leading by 6 months, are computed. The seasonal variations in the interaction between the subtropical high systems over the North Pacific and the equatorial East Pacific SST are discussed. It is found that the surface subtropical anticyclone over the eastern part of the North Pacific is negatively correlated to the equatorial East Pacific SST which lags behind the former on the average by 2-3 months, and the correlation between them is best in spring and poorest in autumn. The feedback impact of the equatorial East Pacific SST on the subtropical high in the middle troposphere behaves differently in different part of this high. Its effect on the main body of subtropical high that has a positive correlation with the SST with the latter leading on the average by 4 months is largest in winter half year and smaller in summer half year, especially in mid-summer. While the effect on the subtropical ridge over the West Pacific that shows negative correlation with the SST with the latter leading on the average by 2-3 months is largest in summer half year and smaller in winter half year. Their transition periods are May and November. Further, some possible causes of such seasonal variations are suggested, in which we emphasize the significance of seasonal variation in the basic state of the background flow, especially in the mean zonal and meridional circulation and their interaction.