Term: mesosphere https://doi.org/10.1351/goldbook.M03855 Definition: That region of the atmosphere which lies above the stratopause (about 4752 km) and below the mesopause (about 8090 km) and in which temperature decreases with increasing height; this is the region in which the lowest temperatures of the atmosphere occur. Related Terms: 1) stratopause (http://doi.org/10.1351/goldbook.S06042). 2) mesopause (in atmospheric chemistry) (http://doi.org/10.1351/goldbook.M03848). Source: PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2201 (https://doi.org/10.1351/pac199062112167) Citation: 'mesosphere' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.M03855 License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.