Relationships Among the Stratospheric and Tropospheric Zonal Flows and the Southern Oscillation

Abstract

Relationships among the high-latitude stratospheric zonal wind, the tropospheric zonal wind in the region of the subtropical jet and over the equator, the Southern Oscillation, and the stratospheric tropical quasi-biennial oscillation (QBO) were examined from monthly anomaly data for 13 years (1968?80). Patterns of correlation wore found which are broadly consistent with the theory on vertical and latitudinal Rossby wave propagation, with high correlations diminishing rapidly in association with easterly basic flow. Lag correlations as high as 0.8?0.9 were found for leads of ?1?7 months, based on three-month average anomalies for successive months. The simplified lead path is from Southern Oscillation to equatorial winds to subtropical winds to stratospheric high-latitude winds. Relationships involving the QBO appear weak compared to those involving the extratropical flows, the tropospheric equatorial flow of the east Pacific, and the Southern Oscillation. Even so, the structure of correlation found between the stratospheric high-latitude winds (or height gradients) and the QBO is consistent with ?compositing? results of Holton and Tan (1980, 1982); moreover, the correlations found between the stratospheric high-latitude flow and the Southern Oscillation are consistent with compositing results of van Loon et al. (1982). Spectra for the variables examined all show a quasi-biennial signal, but coherences involving the QBO at periods 20?30 months were found to be weak to moderate, whereas coherences involving other pairs of variables were moderate to strong.