A ground-based microwave radiometer for detecting tropospheric and mesospheric water vapour

Describes a water vapour radiometer-spectrometer which measures the sky brightness temperature at 21.2, 22.2 and 31.5 GHz at an arbitrary elevation angle. Since the retrieval algorithm does not depend on local parameters the determination of the integrated precipitable water vapour (IPWV) and integrated liquid water (ILW) or the corresponding path delay is possible without calibrating the system with radiosonde data at the observing site. The retrieval is performed with a simplified model of the troposphere and a propagating model developed by Liebe (1985). The combination of both allows the estimation of the tropospheric absorption, emission and dispersion at other frequencies than the operating frequencies (20 and 30 GHz) of the water vapour radiometers