Spectral comparison of ENSO and stratospheric zonal winds

Abstract

The 12-monthly running means of stratospheric low latitude zonal winds at 10, 15, 20, 30, 40, 50, 70 mb, Southern Oscillation Index represented by Tahiti - Darwin atmospheric mean sea level pressure difference (T - D) and equatorial eastern Pacific sea surface temperature (SST) were subjected to maximum entropy spectral analysis for the whole period 1953-1995 as also for its portions. The SST and (T - D) had similar periodicities, as expected, the majormost at ca. 4.5 years and other smaller ones in the quasi-biennial and quasi-triennial regions. The stratospheric winds had the most prominent periodicity at ca. 2.17 years (26 months) in the early years, which changed to ca. 2.22 years (26.5 months) in the middle and ca. 2.50 years (30 months) in recent years, and had other minor periodicities. Some of the wind periodicities matched some of the SST, (T - D) periodicities during some intervals, indicating possible partially common origins and/or mutual influences.