A new methodology for measuring traveling quasi-5-day oscillations during sudden stratospheric warming events based on satellite observations

Abstract

Enhancements of stationary planetary waves (SPWs) and traveling planetary waves (TPWs) are commonly observed in the middle atmosphere during sudden stratospheric warming (SSW) events. Based on the least squares fitting method (Wu et al., 1995), numerous studies have used satellite measurements to investigate the characteristics of TPWs during SSWs, but they have ignored the effect of the SPWs. However, a rapid and large change in the SPWs during SSWs may lead to significant disturbances in the amplitude of derived TPWs. In this study, we present a new methodology for obtaining the amplitudes and wave numbers of traveling quasi-5-day oscillations (Q5DOs) in the middle atmosphere during major SSWs. Our new fitting method is developed by inhibiting the effect of a rapid and large change in SPWs during SSWs. We demonstrate the effectiveness of the new method using both synthetic data and satellite observations. The results of the simulations indicate that the new method can suppress the aliasing from SPWs and capture the real variations in TPWs during SSWs. Based on the geopotential height data measured by the Aura satellite from 2004 to 2021, the variations in traveling Q5DOs during eight midwinter major SSWs are reevaluated using the new method. The differences in the fitted amplitudes between the least squares fitting method and the new method are usually over 100 m during the SSW onsets. Our analysis indicates that previously reported Q5DOs during SSWs might be contaminated by SPWs, leading to both overestimation and underestimation of the amplitudes of the traveling Q5DOs.