Influence of solar UV irradiance on quasi-biennial oscillations in the Earthʹs atmosphere Original Research Article

A study of relationships between variations in the solar ultraviolet (UV) irradiance and quasi-biennial oscillations (QBO) of mean zonal wind in the Earthʹs equatorial stratosphere has been carried out with use of the composite MgII index as a proxy for the solar UV irradiance. The middle-term changes in the UV-irradiation have been separated after removing the long-term (≈11 years) and short-term (≈27 days) variations. The results of the analysis show that the average UV irradiance tends to be higher for east QBO-phase and lower for west phase. The detail analysis of rotation in the stratospheric wind profiles reveals that the quiet periods alternate with active periods, characterizing by strong disturbing winds. Some of these stages occur only in certain seasons, which implies that they are guided by the internal atmospheric mechanisms. Duration of active stages can be affected by level of the UV irradiance. Conclusion is made that variability of the QBO-phase duration in the equatorial stratosphere can be interpreted if influence of the solar UV medium-term variation on basic stratospheric processes is taken into account.