Chemical Composition of the Middle Atmosphere and Its Changes in the 21st Century

The chemical composition of the middle atmosphere (composed of the troposphere, stratosphere, and mesosphere) and its changes in the 21st century are considered. The initial data were obtained from the interactive two-dimensional radiation–chemical model SOCRATES, which calculates the height profiles of components with a resolution of 1 km in the latitudinal zone from 85° S to 85° N, with a step of 5°. The initial conditions were taken to be the Intergovernmental Panel on Climate Change (IPCC) RCP 4.5 scenario for June and January of 2000 and 2100 at a latitude of 50° N. For these conditions, the height profiles and the total content of the long-lived components N₂O, CH₄, and CO₂; chlorofluorocarbons (CFCs) CFC-10 (CCl₄), CFC-11 (CCl₃F), CFC-12 (CCl₂F₂), CFC-113 (CCl₂FCClF₂), CFC-114 (CClF₂CClF₂), CFC-115 (CClF₂CF₃), halon-2011 (CBrClF₂), and halon-1301 (CBrF₃), hydrochlorofluorocarbon (HCFC) HCFC-22 (CHClF₂); acids HF, HCl, HBr, and HNO₃; atmospheric trace gases O(³P), O(1D), H, OH, HO₂, H₂O₂, Cl, Cl₂, ClO, OClO, HOCl, ClONO₂, ClNO₂, Cl₂O₂, N, NO, NO₂, NO₃, N₂O₅, HO₂NO₂, Br, BrO, HOBr, BrONO₂, and BrCl, as well as the chemical families O_x (O₂ + O(³P)), HO_x (OH + HO₂), NO_x (NO + NO₂ + NO₃), ClO_x (Cl + ClO), and BrO_x (Br + BrO). Among other conclusions, it has been shown that for June 2100, the relative change (in %) in the total content of components in the ClO_x, O_x, BrO_x, NO_x, and HO_x families in the stratosphere, in comparison with June 2000, would be–57.5%, +4.0%,–25.7%,–13.9%, and–4.1%, respectively. For January, the corresponding values for ClO_x, O_x, BrO_x, NO_x, and HO_x are–59.1%, +7.3%,–26.2%,–7.1%, and–3.6%, respectively. Similar comparisons have been made for the other components mentioned above. Almost all chemically active components are highly sensitive to the season change.