Space is black as the empty space does not reflect light. The value indicates the percentage of sunlight reflected from the surface. In the thermal infrared channel 2 cold surfaces are light, and warm surfaces are dark. Like in channel 1 clouds appear as light areas, but there are significant differences. The lightest clouds are the coldest and must consequently be the highest in the atmosphere.
Temperature drops with height above the surface of the earth.
The darker the cloud formation, the lower it is in the atmosphere. On infrared images it can be difficult to distinguish between low-lying clouds and cloudless areas, because the temperature difference between the cloud and a wet surface on the Earth can be quite insignificant. Space is white in these images as it does not radiate thermal infrared energy. The radiation received by the satellite in this channel comes from the content of otherwise invisible water vapour in the atmosphere. It is thus possible to analyse the transport of water vapour, which contains large quantities of latent energy.