Method for assessing the amplitude modulation of the stationary planetary waves

Abstract. This short-communication presents a new method for assessing the amplitude modulation of the stationary planetary waves (SPWs). The suggested procedure allows estimating the contribution of the amplitude modulated SPWs to the field of the zonally travelling planetary waves. The root of the method consists in calculating of a quantity that is analogous to 2-D Lomb-Scargle amplitude spectrum and also the relative error of the approximation. The amplitude "spectra" of the SPWs give information about the period(s) of modulation, while the relative errors - define the coefficient(s) of modulation. The suggested method is applied to the UKMO temperature data for the Arctic winter of 2004–2005.