TCCON project glossary

This is a description of technical terms used in the Total Carbon Column Observing Network project page.

anthropogenic – due to human activities

atmospheric mixing – transport of gases or emissions away from their source and dilution (horizontally or vertically), by winds convection and turbulence.

Fourier Transform Spectrometers (FTS) in this context, are instruments used to measure the absorption of sunlight by molecules in the atmosphere. Sunlight is made up of many different wavelengths of light (the spectrum). The FTS measures how much of each wavelength is absorbed along the line of sight between the instrument and the sun. Each gas has characteristic light absorption properties. Using mathematical models, scientists can use the data from the FTS to infer the number of absorbing molecules of a given gas on the light path through the atmosphere. This is then converted to the number of molecules in a virtual vertical column (the 'total column'). An FTS can be based on the ground or onboard satellites. (For more technical details on Fourier Transform Spectroscopy see:

global carbon cycle – the biogeochemical cycle by which carbon is exchanged among the Earth’s atmosphere, terrestrial biosphere (including freshwater, plants, animals, and soils), oceans, and sediments.

greenhouse gases – gases that absorb and emit infrared radiation reflected from the Earth’s surface. Part of the absorbed radiation is re-emitted back downwards towards the Earth, warming the air and the Earth's surface – the so called ‘greenhouse effect’. The main greenhouse gases in the Earth’s atmosphere are: water vapour, carbon dioxide, methane, nitrous oxide, and ozone. (See also:

in situ gas analysers – instruments that sample air at a given location to measure trace gas concentrations. These can be ground-based or deployed in a plane and use tanks of air of known gas concentrations (calibration tanks) to relate air measurements to the standard WMO reference scale for greenhouse gases.

surface fluxes – transfer of gases between the surface of the Earth or ocean and the atmosphere.

total column measurements – the number of molecules of a particular gas (e.g. carbon dioxide) in a virtual column extending from the Earth’s surface to the top of the atmosphere.