NOVOSIBIRSK, March 27. /TASS/. Scientists at the St. Petersburg State University discovered an increase in toxic tropospheric ozone in Siberia in summer, which may be related to forest fires, the university's press service told TASS.

Ozone plays a key role in the Earth's climate system. Stratospheric ozone protects the biosphere from ultraviolet radiation and determines the radiation balance, while tropospheric ozone is a greenhouse gas and an air pollutant. Its study is especially important for Russia because of the vulnerable Arctic Zone and northern latitudes, as well as due to the vast territory and uneven distribution of pollution sources. However, despite the satellite systems, a comprehensive analysis of regional trends over the Russian Federation had not been detailed enough.

"Physicists at the St. Petersburg State University conducted large-scale modeling of the total and tropospheric ozone contents over the Russian territory in different seasons. They have found that toxic tropospheric ozone grows in Siberia in summer, which may be related to forest fires," the university said.

The study results are published in the Atmosphere scientific journal. During the study, scientists used data from IKFS-2, a Russian satellite instrument, which measures outgoing thermal radiation. To interpret measurements and to model the processes, the scientists used two models of different scales: a global chemical and climatic model and a high-resolution regional model. The simulation covered most of the Russian territory, taking into account anthropogenic emissions, biogenic sources and emissions from fires. Experts compared the model data with satellite measurements to evaluate calculations accuracy and to identify patterns of ozone distribution fields.

"Having analyzed data, we found clear seasonal and regional differences. In the Siberian regions, the maximum tropospheric ozone is observed in July, which is associated with intensive photochemical formation at high temperatures, as well as with emissions from forest fires. As for the European part of Russia and the Arctic Zone, the gas content's peak is shifted to April-May," the press service quoted one of the study's authors Yana Virolainen as saying.

The work

The model successfully reproduced anomalous values using data of the summer of 2021, when tropospheric ozone levels increased due to extreme fires in Siberia and Yakutia. The gas content indicators follow global patterns. Maximum levels in the winter - spring period are observed over the eastern regions (the Far East, Kamchatka, the Sea of Okhotsk), and minimum levels in the summer - autumn period are in the Arctic latitudes.

Scientists now understand why in certain years ozone amounts may drop significantly in spring. This happens when two natural phenomena coincide: the so-called positive phase of the Arctic oscillation and a certain direction of stratosphere winds. During such periods, a stable cold vortex forms up over the North Pole, inside of which emerge conditions to destruct ozone molecules. This was absolutely evident in 2011 and 2020, when scientists reported record low ozone levels over the Arctic.