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The staff of the Department of Atmospheric Physics and Microwave Diagnostics of the A.V. Gaponov-Grekhov Institute of Applied Physics of the Russian Academy of Sciences investigated previously unexplored features of chemical processes in the so-called mesopause region. This area is located at altitudes from about 80 to 100-105 km, i.e. near the lower boundary of space, and is by far the least studied part of the Earth's atmosphere. It records a number of unique phenomena and processes that are of both fundamental and practical interest. In particular, at these altitudes, the air temperature can drop to the lowest values in terrestrial conditions (up to -173 ° C), which makes this area particularly sensitive to observed climatic changes and anthropogenic effects on the composition of the atmosphere. The method developed earlier at the IAP RAS for determining the lower boundary of the high-altitude region of the chemical equilibrium of night ozone was applied to the analysis of data from global three-dimensional modeling of physico-chemical processes in this area of the atmosphere. First of all, the presence of a sharp (in height) transition zone was revealed, which separates fundamentally different modes of daily variability of small gas impurities. The vertical variability of the position of this zone in height reflects the dynamics of many phenomena, for example, the formation of layers of atomic oxygen and hydrogen and the regions of luminescence of a number of atoms and molecules initiated by them. These lights are well recorded from the Earth's surface and are used as indicators of global climate change. In addition, it was found that the boundary of the equilibrium of night ozone according to the developed criterion clearly tracks the altitude position of the transition zone, therefore, determining this boundary according to satellite sensing data, it is possible to study the spatiotemporal variability of physico-chemical processes in the mesopause region. In this regard, the analysis of the global (from 83 °c to 83 °C) long-term evolution of the equilibrium boundary of night ozone according to SABER/TIMED (NASA) satellite data for 2002-2021 was carried out. It was revealed that this characteristic is a sensitive indicator of atmospheric dynamics with different spatial and temporal scales. In particular, a strong sensitivity to sudden stratospheric warming and elevated phenomena (from the usual 40-60 km to ~80 km) of the stratopause was found, and annual variations at low and middle latitudes demonstrate a clear signal of the 11-year solar cycle.

The results of the work open up new possibilities for exploring this hard-to-reach area of the Earth's atmosphere. The work was supported by the Russian Science Foundation 22-12-00064 (https://rscf.ru/project/22-12-00064 /).

Publication: Kulikov M.Yu., Belikovich M.V., Chubarov A.G., Dementeyva S.O., Fegin A.M., Boundary of nighttime ozone chemical equilibrium in the mesopause region: long-term evolution from 20-year satellite observations // Atmospheric Chemistry and Physics, 23, 14593-14608, https://doi.org/10.5194/acp-23-14593-2023 , 2023.

Image: Altitude-time variations of O and H concentrations obtained using a three-dimensional chemical transport model. Concentrations are normalized to local (in height) average daily values, respectively. Dark stripes are daytime, light stripes are nighttime. The black lines show the boundary of the equilibrium region of night ozone according to the criterion. Source: IPF RAS Press Service

Information and illustration provided by the press service of the IPF RAS

Information taken from the portal "Scientific Russia" (https://scientificrussia.ru /)