Measuring ozone
The abundance of ozone in the atmosphere is measured by a variety of techniques that make use of ozone’s unique optical and chemical properties. There are two principal categories of measurement techniques: local and remote. Both ozone measurement techniques have been essential in monitoring changes in the ozone layer and in developing our understanding of the processes that control ozone abundances.
Ozone is measured throughout the atmosphere with instruments on the ground, aircraft, high-altitude balloons, and satellites. Some instruments measure ozone locally in sampled air and others measure ozone remotely a considerable distance away from the instrument. Instruments use optical techniques with either the Sun (direct, reflected, or scattered radiation) or lasers (green lines) as light sources; detect the thermal emissions from ozone and other atmospheric molecules (not shown); or use chemical reactions that are unique to ozone (ozonesonde). Ref: Ross J. Salawitch (Lead Author) et al., "Twenty Questions and Answers About the Ozone Layer: 2022 Update, Scientific Assessment of Ozone Depletion: 2022", 75 pp., World Meteorological Organization, Geneva, Switzerland, 2023.
Local measurements
Local measurements of the atmospheric abundance of ozone are those that require air to be drawn directly into an instrument. Once inside an instrument’s detection chamber, the amount of ozone is determined by measuring the absorption of ultraviolet (UV) light or by the electrical current or light produced in a chemical reaction involving ozone. The last approach is used in “ozonesondes”, i.e. lightweight, ozone-measuring modules suitable for launching on small balloons. Local ozone-measuring instruments using optical schemes are also used on commercial aircraft to measure the distribution of ozone in the troposphere (e.g. IAGOS).
Remote measurements
Remote measurements of total ozone amounts and the altitude distributions of ozone are obtained by detecting ozone at large distances from the instrument. Ground-based spectrophotometers measure the total ozone amount by detecting small changes in the amount of the Sun’s UV radiation that reaches the Earth’s surface. But also several satellite instruments use the absorption of solar UV radiation by the atmosphere or the absorption of sunlight scattered from the surface of Earth to measure ozone on a daily basis, and over nearly the entire globe. Other instruments measure ozone using its absorption of infrared or visible radiation or its emission of microwave or infrared radiation at different altitudes in the atmosphere, thereby obtaining information on the vertical distribution of ozone.