Abstract
When quasi-triennial periodicities have been found in climatic data, their presence has often been attributed to QBO-SO interaction. Although a mixture of idealized QBO and SO signals can give rise to a quasi-triennial carrier wave modulated at the sunspot-cycle period, neither of the latter periods appears in spectral analysis of the resultant time series. It is therefore concluded that quasi-triennial spectral peaks are more likely to be of physical origin than a result of QBO-SO interaction.
