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Abstract
Abstract. Our analysis of temperature and zonal wind data (1958 to 2006) from the National Center for Atmospheric Research (NCAR) reanalysis (Re-1), supplied by the National Centers for Environmental Prediction (NCEP), shows that the hemispherically symmetric 12-month equatorial annual oscillation (EAO) contains spectral signatures with periods around 11 years. Moving windows of 44 years show that, below 20 km, the 11-year modulation of the EAO is phase locked to the solar cycle (SC). The spectral features from the 48-year data record reveal modulation signatures of 9.6 and 12 years, which produce EAO variations that mimic in limited altitude regimes the varying maxima and minima of the 10.7 cm flux solar index. Above 20 km, the spectra also contain modulation signatures with periods around 11 years, but the filtered variations are too irregular to suggest that systematic SC forcing is the principal agent.
Highlights
1.1 Solar cycle effectsIn several papers, solar cycle (SC) effects have been linked to the quasi-biennial oscillation (QBO), which dominates the zonal winds of the lower stratosphere at equatorial latitudes
Solar cycle (SC) effects have been linked to the quasi-biennial oscillation (QBO), which dominates the zonal winds of the lower stratosphere at equatorial latitudes
Salby and Callaghan synthesized these spectral features to produce the filtered SC modulation of the QBO embedded in the data, which shows at 20 km zonal wind variations from about 12 to 20 m/s that are correlated with the 10.7 cm flux
Summary
Solar cycle (SC) effects have been linked to the quasi-biennial oscillation (QBO), which dominates the zonal winds of the lower stratosphere at equatorial latitudes. With a 2-D model extending from about 15 to 30 km, Cordero and Nathan (2005) simulated the observed SC modulation of the QBO, which is driven with prescribed Kelvin waves and Rossby gravity waves. In this model, the SC effects on ozone influence the wave interaction to generate variations of the QBO amplitude that are in phase with the observed zonal winds reported by Salby and Callaghan (2000). Mayr et al (2006) simulated the observed SC effect with a 3-D model, which relies primarily on parameterized gravity waves (GW) to produce the QBO. Mayr et al.: Solar cycle signatures in the NCEP equatorial annual oscillation symmetric equatorial annual oscillation (EAO) that acts as pacemaker (Mayr et al, 2005)
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