| Summary: | Maintenance and Update Frequency: continual Statement: Infrared (IR) images IR images are derived from radiation emitted from the Earth and its atmosphere at thermal-infrared wavelengths (10-12 µm). They provide information on the temperature of the underlying surface or cloud. IR images are available 24 hours per day because temperatures can always be measured, regardless of day or night. (This is in contrast to Visible images which are only available during the day. See below). The temperatures are represented either by a grey-scale (black is no-cloud, and increasing white means higher colder clouds), or in a colour scheme. IR imagery is available on: * NOAA 17 and NOAA-18: Channel 4: 10.3-11.3 µm Channel 5: 11.5-12.5 µm * MTSAT-1R: Channel 4: 10.3-11.3µm Channel 5: 11.5-12.5 µm * FY-2C: IR1: 10.5-12.5 µm * More information on IR images Visible images Visible (VIS) images are a record of the visible light scattered or reflected towards the satellite from the Earth and clouds. i.e. you can 'see' the clouds. Visible images give meteorologists extra information that may not appear on Infrared temperature images. For example, fog appears in Visible images, but may not in Infrared images when the fog and the land are at the same temperature. Visible images are only available during the daytime, because at night the world looks black. VIS images are normally displayed in a manner similar to that seen by the human eye. Using a black and white colour scale, with different shades of grey indicating different levels of reflectivity, the brightest and most reflective surfaces are in white tones and the least reflective in black. In general, clouds are seen as white objects against the darker background of the earth's surface. Visible imagery is available on: * NOAA 17 and NOAA-18: Channel 1: 0.58-0.68 µm Channel 2: 0.725-1.10 µm * MTSAT-1R: Channel 1: 0.55-0.90µm * FY-2C: VIS 0.5-1.05 µm * More information on VIS images Water Vapour channel Water Vapour imagery is derived from radiation emitted by water vapour at ...
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