Opposition of anomalies of upper tropospheric winds at Singapore and Canton Island

Anomalies in monthly mean upper tropospheric zonal winds at Canton Island and Singapore tend to be of opposite sign in the same month. Correlation coefficients have been computed, for each quarter, between monthly anomalies at 150 mb at Canton Island and at 50,000 feet at Singapore, using twelve years' data. All were negative: the largest negative value was -0.65 in the December-February quarter. This opposition is associated to some extent, most strongly in December-February, with variations of the Southern Oscillation, as represented by the departures from average of the monthly mean Papeete (Tahiti) minus Darwin pressure difference. When this index is positive, stronger than normal upper west winds occur at Canton Island and stronger than normal upper east winds at Singapore. The amplitude and phase of the 26-month oscillation at each station, at the levels considered, was found by harmonic analysis. The amplitudes were two knots at Canton Island and one knot at Singapore. There was a phase difference of 11 months between the two stations. Hence the 26-month oscillation is not simply propagated downward from the stratosphere at all longitudes.