Data points on the interannual time scale jump between the first and third quadrant, keeping the same polarities in the northern and southern tropics for most of time. As the monopole index, we calculated the sum of zonal mean SST anomalies between 10-20 degree latitudes in either side of equator. For the monopole index, only the tropics have substantial regressed SST anomalies (not shown). Interannual variability in the tropical Atlantic is rather associated with the El Nino-Southern Oscillation (Enfield 1997).
4. Summary
1) Tropical SST anomalies have two major components of the dipole structure on decadal time scales and monopole structure on interannual time scales.
2) The Pan-Atlantic decadal oscillations of SST and SLP fields are much associated with the tropical dipolar oscillation. NAO pattern appears when the tropical dipole is developed. This indicates the extratropics-to-tropics linkage.
Acknowledgment
Authors express a special thank to Dr. J. P. McCreary for his beneficail comments. He and Dr. Jacques Servain also gave us an opportunity to attend the PIRATA-5 meeting in November 1998. It benefits us to develop this research.
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