Journal OACI

No. 10

Cloud top temperature photograph of the volcanic plume rising from El Chichon (Mexico) one day after its eruption of 28 March 1982. A very high resolution radiometer on the NOAA-7 satellite measures radiation from Earth and its atmosphere in the infrared (IR) range. Cloud height is determined by comparing IR data with temperature profiles obtained by radiosonde. Colour progression in the photograph from green to yellow to red indicates a decrease in temperature. The centre of the cloud is colder than the edges owing to its higher altitude.