Updated total ozone climate normals over the territory of Ukraine

The study presents the results of analysis of spatiotemporal distribution of updated total ozone climate normals for the period of 1991–2020. It analyzes the changes since the last total ozone climate normals estimate conducted for the period of 1981–2010. The daily data retrieved using TOMS and OMI satellite instruments over the territory of Ukraine allowed calculation of multiyear average values, climate normals for each day of the year, amplitudes, phases and determination coefficients for total ozone seasonal variations. Use of the NCEP/NCAR reanalysis data allowed establishment of the relation between total ozone and meridional wind changes in the lower stratosphere. The research shows the existence of the regions with higher/lower total ozone content that are not in line with the characteristics of latitudinal distribution. They are formed due to more frequent recurrence of air advection with ozone content that is not typical for the Ukrainian territory, mostly from January to March. The study describes a typical temporal distribution of the total ozone climate normals varying from 285 to 375 Dobson units (D.u.) and analyzes the statistic patterns of deviations distribution and recurrence of extremely high/low total ozone content. The paper emphasizes a small variation of total ozone over the territory of Ukraine. The authors also researched the features of spatial distribution of seasonal variation amplitudes varying within the range of 42–46 D.u. and the specifics of maximum values periods observed from 19 to 30 of March, depending on a region. It was established that, since the previous update of the climate normals, the total ozone decreased for all months with its maximum decrease of about 8 D.u. in winter. However, no increase of recurrence of ultraviolet radiation high levels was observed. Total ozone changes are mainly associated with shifts of meridional wind values to negative ones. This process indicates the increase of recurrence of air advection from the north. The paper also emphasizes the complexness of total ozone changes during the period of research and the lack of consistency of such changes with the circulation factor of summer months.