Satellite-Borne Measurements of the Composition of the Middle Atmosphere

Atmospheric dynamics and photochemistry can be studied by using measurements of temperature and composition made by remote sensing from satellites. This paper describes the pressure-modulation technique, which is employed by the stratospheric and mesospheric sounder (SAMS) experiment on the satellite Nimbus 7, and by an advanced version (the improved stratospheric and mesospheric sounder or ISAMS) now under construction for the forthcoming Upper Atmosphere Research Satellite programme. SAMS measurements of methane and nitrous oxide for the three-year period from 1 January 1979 to 31 December 1981 are presented, and show the latitudinal and seasonal variability of the average concentration of these long-lived minor constituents. From the observed behaviour, some aspects of the circulation of the middle atmosphere are identified and their possible origins discussed.