Interannual vartability of the Northern Hemisphere polar vortex at the 30mb during 21 winter seasons is examined making use of two indices which may be viewed as measures of the intensity of the vortex. The signature of stratospheric warmings is clearly evident in time series of the indices, but these events account for only part of the interannual variability. Alleged relationships between the intensity of the wintertime stratospheric polar vortex and the phase of the equatorial stratospheric

more »

... uasi-biennial oscillation and the tropical tropospheric Southern Oscillation are examined, making use of the same indices. Both relationships show up quite distinctly in our analysis but neither one is consistent with the anomalies in the intensity of the polar vortex during all winters.