Revisiting the Quasi-Biennial Oscillation as Seen in ERA5. Part II: Evaluation of Waves and Wave Forcing

This paper describes stratospheric waves in ERA5 reanalysis and evaluates the contributions of different types to driving quasi-biennial oscillation (QBO). Because its higher spatial resolution compared predecessors, is capable resolving a broader spectrum waves. It shown that resolved contribute both eastward westward accelerations near equator, mainly by way vertical flux zonal momentum. The are due Kelvin small-scale gravity (SSG) with wavelengths smaller than 2000 km, whereas forced SSG waves, from inertio-gravity mixed-Rossby-gravity Extratropical Rossby propagate into tropical region impart acceleration flow. They appear be responsible for at least some irregularities QBO cycle.