Microwave (MW) radiometers that use absorption bands to look at frequencies where certain gases in the air (mainly oxygen and water vapour) absorb very strongly. That means radiation coming up from lower in the atmosphere or from the surface is quickly weakened (“attenuated”) as it passes through the atmosphere. Different frequencies mainly ‘see’ different altitudes. By combining measurements at several nearby frequencies in such a band, it is possible to infer how temperature and moisture change at different altitudes.
