Satellites measure ozone by detecting the amount of solar ultraviolet (UV) radiation that penetrates through the stratospheric ozone layer.
Here's a breakdown of how this works:
The Principle: Ozone Absorbs UV Radiation
The ozone layer in the Earth's stratosphere absorbs a significant portion of the sun's harmful UV radiation. The more ozone present, the less UV radiation reaches the Earth's surface. Therefore, by measuring the amount of UV radiation that does get through, scientists can infer the amount of ozone present.
Satellite Instruments: TOMS and Others
Satellite instruments, such as the Total Ozone Mapping Spectrometer (TOMS) and its successors, are designed to measure UV radiation at different wavelengths.
The Measurement Process:
- Sunlight as a Source: The sun emits UV radiation across a range of wavelengths.
- Absorption by Ozone: As sunlight passes through the atmosphere, ozone molecules absorb UV radiation, particularly in the UV-B and UV-C ranges.
- Satellite Detection: Satellite instruments measure the intensity of UV radiation at specific wavelengths after it has passed through the atmosphere and been partially absorbed by ozone.
- Comparison and Calculation: The instruments compare the measured UV intensity at wavelengths that are strongly absorbed by ozone to those that are weakly absorbed. The difference in intensity provides a measure of the total ozone column (the total amount of ozone in a vertical column of the atmosphere).
- Ozone Mapping: By scanning across the Earth, these instruments can build up a map of ozone concentrations globally.
Example: How Reduced Ozone is Detected
If a satellite instrument detects a higher-than-normal level of UV radiation at wavelengths typically absorbed by ozone, this indicates a reduction in the ozone layer. This is, in essence, how ozone depletion (like that in the ozone hole over Antarctica) is monitored.
Instruments other than TOMS
While TOMS is a well-known example, many other satellite instruments, such as the Ozone Monitoring Instrument (OMI) and the Tropospheric Monitoring Instrument (TROPOMI), also use similar principles to monitor ozone levels.
