Abstract. The quasi-stationary asymmetry of total ozone over Antarctica during spring is studied by TOMS data during the period . Statistics on the amplitude and longitudinal position of zonal anomalies are obtained from the distribution of total ozone along seven individual latitudes at 5-degree intervals between 50 • S and 80 • S. As shown by the September-November means, the mid-latitude collar of ozone-rich stratospheric air has a sub-Antarctic maximum with a mean location in the quadrant 90 • E-180 • E and a total ozone level of about 380 DU between 50 • S and 60 • S. The steady displacement and elongation of the ozone hole under the influence of planetary waves causes a zonal anomaly of low ozone in the sector 0 • -60 • W with total ozone levels of about 200 DU between 70 • S and 80 • S. Climatologically, the highest amplitude of the zonal anomaly is 57.2±13.5 DU (relative asymmetry of 32% between high and low ozone levels) at 65 • S latitude.A significant eastward shift of approximately 45 • in longitude is observed in the total ozone minimum over the Weddell Sea -South Atlantic sector during 1979-2005, whereas the zonal maximum is relatively stable in location. Also apparent is a long-term shift in tropopause temperature distribution in the region.The geographical distribution of the zonal extremes in total ozone for the seven latitudes shows that (i) the extremes exhibit sensitivity to the shape of the Antarctic continent, (ii) the stationarity of the extremes increases poleward above the edge of continent and (iii) the positions of the extremes at the higher latitudes tend to follow the meridionally oriented elements of orography. It is suggested that the radiative influence of Antarctica contributes to the formation of this pattern. Anomalies in the horizontal structure of the tropopause, which appear related to orography, support this view.Correspondence to: G. P. Milinevsky (gmilin@univ.kiev.ua) Mechanisms involved in the formation and decadal change in the total ozone asymmetry, as well as possible influences of the asymmetry on the stratospheric thermal regimes and regional UV irradiance redistribution are discussed.

The impact of a major sudden stratospheric warming (SSW) in the Arctic in February 2018 on the midlatitude mesosphere is investigated by performing the microwave radiometer measurements of carbon monoxide (CO) and zonal wind above Kharkiv, Ukraine (50.0 • N, 36.3 • E). The mesospheric peculiarities of this SSW event were observed using a recently designed and installed microwave radiometer in eastern Europe for the first time. Data from the ERA-Interim and MERRA-2 reanalyses, as well as the Aura microwave limb sounder measurements, are also used. Microwave observations of the daily CO profiles in January-March 2018 allowed for the retrieval of mesospheric zonal wind at 70-85 km (below the winter mesopause) over the Kharkiv site. Reversal of the mesospheric westerly from about 10 m s −1 to an easterly wind of about −10 m s −1 around 10 February was observed. The local microwave observations at our Northern Hemisphere (NH) midlatitude site combined with reanalysis data show wide-ranging daily variability in CO, zonal wind, and temperature in the mesosphere and stratosphere during the SSW of 2018. The observed local CO variability can be explained mainly by horizontal air mass redistribution due to planetary wave activity. Replacement of the CO-rich polar vortex air by CO-poor air of the surrounding area led to a significant mesospheric CO decrease over the station during the SSW and fragmentation of the vortex over the station at the SSW start caused enhanced stratospheric CO at about 30 km. The results of microwave measurements of CO and zonal wind in the midlatitude mesosphere at 70-85 km altitudes, which still are not adequately covered by ground-based observations, are useful for improving our understanding of the SSW impacts in this region.

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Rapid climate warming has been observed in the region of the Antarctic Peninsula since the middle of the last century with the largest warming rate in the winter. Decadal variability of winter temperature on the regional scale was analysed using eight station datasets of the Antarctic Peninsula region. The Scientific Committee on Antarctic Research Reference Antarctic Data for Environmental Research from the period 1950-2009 were used. Fourier and wavelet transforms of the averaged temperature anomaly time series reveal a clear separation between the oscillations with three to eight year periods and a decadal oscillation with a period of around 16 years. On the Antarctic Peninsula region scale, 16 year periodicity in the winter temperature variability has not been described before. Both spectral components show similar spectral power and statistical significance (5-10%). This is evidence of their comparable importance for winter temperature changes in the Antarctic Peninsula region. The three to eight year periods are most probably related to the El Niño-Southern Oscillation and Antarctic Circumpolar Wave signals, but the 16 year oscillation has not been identified within the scope of this analysis. The possible effect of the decadal oscillation in the winter temperature trend estimate is discussed.

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