Eastward travelling waves in the southern hemisphere stratosphere during the spring of 1983

This paper presents a case study of planetary waves in the southern hemisphere stratosphere during the spring of 1983, using the global temperature and geopotential height data provided by the United States National Meteorological Center (NMC). the eastward travelling wave of zonal wavenumber 2 with a period of 9.2 days persisted from mid September to early November. It had a phase structure which showed only slight tilt with height and latitude, while the quasi‐stationary wave 1 tilted westwards with increasing height and towards the equator. During the vigorous period of the eastward travelling wave 2, the amplitude of the quasi‐stationary wave 1 varied with a period of about 10 days. This variation was due to a coincidence between the phases of the stationary wave 1 and the eastward travelling wave 2; when the ridges of waves 1 and 2 overlap, wave‐1 amplitude reaches its maximum. the active period of the travelling wave 2 is closely related to the seasonal change in the mean zonal winds. In 1983 the eastward travelling wave 2 became vigorous after the zonal‐mean westerly jet moved rapidly poleward and downward. Compared with the other 5 years for which we have data, the wind structure for the month of September 1983 was peculiar because of the stronger meridional curvature of the westerly jet.