Inter-annual variability of temperature in the upper troposphere and lower stratosphere at Durban

We have investigated the inter-annual variability of temperature in the upper troposphere and lower stratosphere over Durban for the 20-year period from 1980 to 1999. A spectral analysis of morning and afternoon temperatures at four heights (10, 12, 16 and 18 km) revealed a number of oscillations which could be associated with the annual cycle, the Quasi-biennial Oscillation (QBO) and the El Nino/Southern Oscillation (ENSO). The annual and QBO (27 months) cycles were present at 10, 16 and 18 km, with the former being dominant. Peaks at similar to2.7, 4 and 6.7 years were also detected and were linked to ENSO cycles. By contrast, these cycles were either absent or not well developed (in the case of the annual cycle) at a height of 12 km. Possible reasons for this lack of consistency were sought, with the presence of the jet stream at 12 km being a likely explanation.