Microwave Observations of Atmospheric Ozone above Nizhny Novgorod in the Winter of 2017–2018

We present the results of the ground-based microwave measurements of evolution of the vertical ozone content in the middle atmosphere above Nizhny Novgorod (56°20 ' N, 44° E) in the winter of 2017–2018. The results are compared with the satellite-based sensing data obtained using the MLS instrument onboard the Aura satellite and the ERA5 reanalysis data. In particular, the degree of the dependence of the stratospheric-ozone content on the position of the polar-vortex boundary with respect to the observation point at different altitudes is established. It is recorded that in January 2018 the vortex approached the city of Nizhny Novgorod and the boundary of the vortex up to its collapse (February 12), oscillated above the city, so that different altitude levels alternately appeared inside or outside the vortex. Such dynamics of the vortex most noticeably affected the evolution of the stratospheric maximum of the ozone content, whose position followed variation in the vortex boundary and quasiperiodically varied in the altitude range 30–35 km. The results of the ground-based microwave sensing give on the average a lower relative ozone content than the MLS data with a maximum systematic difference of about 0.8 ppm at the altitudes 38–39 km. Nevertheless, we recorded a more distinct response of the ozone content to a change in the structure of the vortex above Nizhny Novgorod than that in the case of using the satellite and reanalysis data.