Micro Wave Radiometer

Microwave radiometer monitors the water vapour absorption line at 22 GHz to determine the water vapour profile as the magnitude of pressure broadening of water vapour absorption line at this frequency decreases with height. Microwave radiometer monitors radiated power in a molecular oxygen absorption band around 60 GHz to determine temperature profiles and radiative power at selected frequencies of 22 to 59 GHz together to determine the liquid water profile. Cloud base height is estimated from zenith-infrared observations and retrieved temperature profiles. The MWR K band channels (22–30 GHz) are calibrated using tipping and V band channels (51–59 GHz) using a patented cryogenic black-body target. These calibrations are automatically transferred to a temperature-stabilized noise source. The internal mirror and azimuthal drive are used to point at any direction in the sky. The brightness temperatures are determined at various frequencies by using Plank’s law and radiative-power observations. These brightness temperatures are used as input to retrieval of the profiles of temperature, relative humidity, liquid water content and vapour density.