Weather satellites observe the atmosphere using different spectral channels. The visible channel (about 0.5–0.9 µm) detects reflected sunlight and is used for daytime cloud and surface mapping; bright areas indicate thick clouds or high albedo, dark areas water or vegetation. The infrared channel (about 10.5–12.5 µm) measures emitted thermal radiation and works day and night; cloud-top temperatures are shown (bright = cold high clouds, dark = warm surface) (EUMETSAT; CIRA/CSU).

The water vapour channel (about 5.7–7.1 µm) senses water vapour in the upper troposphere. Bright values indicate clouds or moist layers, grey shades varying humidity, and dark values dry air. This channel is an absorption measurement: radiation from below is absorbed by water vapour, which then radiates. Water vapour imagery helps identify jet streams, frontal systems, and humidity structure (EUMETSAT; EUMeTrain).

Operational satellites such as EUMETSAT's Meteosat Second Generation (MSG) carry instruments with multiple channels; combinations are used to create RGB products (e.g. airmass) that help forecasters analyse synoptic-scale weather. National meteorological services and agencies like NOAA and EUMETSAT provide imagery and derived products; the data above may come from such sources (e.g. KNMI). WMO coordinates global satellite observing systems.