The observed zonal wind cycle in the southern hemisphere stratosphere

• Published in: Quarterly Journal of the Royal Meteorological Society
• Main Author: Tucker, G. B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1979
• Subjects: polar night
• Online Access: http://dx.doi.org/10.1002/qj.49710544317; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fqj.49710544317; https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.49710544317

Abstract Zonal winds in the stratosphere for a period of 20 years have been analysed at nine stations between 7°S and 66°S centred on the longitude of eastern Australia. The amplitude, period and phase of the third (‘quasi‐biennial’) cycle are determined. Although a coherent pattern emerges in the variation of period with latitude and height it is concluded that, at least in the tropics, the representative period is 832 days (27.35 months). The well‐known maximum in amplitude of this third cycle in the tropics decreases to a minimum at about 30°S but increases again polewards, reaching a maximum at about 50°S at the highest levels of observation (6mb). The phase of the cycle ‘leads’ at high levels and low latitudes and also at the height and latitude of the polar night jet. Below these maxima there is a downward propagation of the cycle but little phase variation with height exists in middle latitudes. For the tropics, the variation with latitude of amplitude and phase is consistent with lateral diffusion of a forced equatorial cycle, with eddy diffusion coefficients of 1 × 10 9 cm 2 s −1 at 80mb, decreasing to 3 × 10 8 cm 2 s −1 at 25mb.