Structure of synoptic-scale waves in the tropical Pacific during July-December 1974-1976

Abstract

Composite wave structures, sea-surface temperatures (SST), and mean zonal winds are studied for the period July through December over the three consecutive years 19 7M-, 1975 and 1976. These three years were found to possess an "average" SST anomaly distribution, a cold anomaly pattern and a warm anomaly pattern respectively. Radiosonde data for the six month period for each year and each of the six locations (Koror, Yap, Truk , Ponape , Kwajalein and Majuro) were analyzed to derive composite wave descriptions of meridional and zonal wind components, temperature and specific humidity. The basic results such as periodicity and structural tilt were generally in agreement with previous research. Combining the SST data, mean zonal flow and wave composites leads to some new insights into the effects of the tropical SST on the semi-permanent Walker circulation and transient easterly waves. Results indicate that the east to west oscillation of the Walker circulation may be directly related to the tropical eastern Pacific SST. It is also shown that the migration of the Walker circulation and subsequent change in the upper- tropospheric flow is directly related to the structural tilt of migratory tropical waves. Consideration of the wave thermal structure and its relation to the SST indicates that the waves energetics may reflect the effects of the upstream SST.