Analysis of Long-Term Measurements of Tropospheric Ozone at the SPBU Observational Site in Peterhof

Abstract

Tropospheric ozone (TO) is one of the major greenhouse gases and a toxic air pollutant. It plays a key role in various chemical and photochemical processes in the troposphere. Ozone concentrations both at surface level and in free troposphere are measured by various local and remote-sensing methods. The SPBU observational site in Peterhof (NDACC site St. Petersburg) is equipped with the Bruker IFS 125HR Fourier spectrometer used for TO measurements and the Thermo Scientific Model 49i gas analyzer for monitoring surface ozone concentrations (SOC). The temporal variability of TO in the 0–8 km layer for the period from April 2009 to October 2022 and of SOC for the period from 2013 to 2021 has been analyzed. Seasonal cycle of TO and SOC is similar to that of total ozone columns, but it is shifted in time by about 1 and 1.5 months, respectively. The maximum variation of TO from the average value for the period falls on the first half of April ~+16%; a minimum of about –(12–14)% is observed from mid-October to the end of December. In the middle of summer, there is also a slight increase in the TO variation at the level of +(7–8)%. A statistically significant decrease in the TO content by 0.34 ± 0.22% per year was also obtained. Comparison of hourly averaged data on TO with synchronized data of SOC measurements revealed an increase in the correlation coefficient (up to 0.5 or more) between the two values 3–4 hours after local noon in the warm season, accompanied by an increase in SOC. The increase in correlations is in good agreement with the increase in the height of the planet boundary layer.