Ozone layer state and level of ultraviolet irradiance over the territory of Ukraine in 2019

Abstract

The paper presents main results of total ozone column (TOC) and levels of ultraviolet irradiance daily monitoring conducted for the Ukrainian territory in 2019. Monitoring and analysis were performed using TOC data measured by the satellite Ozone Monitoring Instrument (the OMI) and estimated values of ultraviolet index. The research was made on the regular grid with 1° spatial resolution and separately for geographical coordinates of centers of Ukrainian administrative regions. In 2019 the TOC ranged within a multiyear average standard with and its average value was equal to 260–360 D.u. During winter ozone concentration reached its highest values due to intensification of Brewer-Dobson circulation. Weakened polar vortex and ozone-rich air masses advection at the upper atmospheric levels which transport high ozone concentrations, resulted in the TOC positive anomalies emergence over Ukraine. The air masses penetrated Ukrainian territory from the north-west and this led to emergence anomalously high TOC values during a number of periods: February 23–24, March 2, March 12–14, March 26. In these periods 450–500 D.u. was a typical ozone content. Seasonal TOC decrease, observed from April to June, was caused by a weakened Brewer-Dobson circulation and intensification of photochemical ozone loss. Nevertheless, TOC deviations from average standard were negligible and this resulted in absence of very high UV-index values. The highest UV-index values did not reach 7 units. In July the TOC was slightly higher than usual concentrations, which was probably caused by dynamic factors. Such TOC values influenced the level of ultraviolet irradiance and the UV-index varied within 3–4 units' range which is typical for Ukraine in April–May. Such ozone state in 2019 made it impossible for UV-index to reach extremely high levels, especially during the summer period. Further TOC changes were characterized by typical seasonal ozone decrease with minimum values observed in October resulted from formation and intensification of polar vortex. Average minimum values in October amounted to 260–270 D.u., however, it is a typical TOC content for this period with a relative deviation from the standard constituting about -0.3σ. Seasonal ozone increase in 2019 started in mid-November. At the end of December the first high positive deviations happened. The highest of them reached close to anomalous 2–2.4σ values.