The Met Office Observation-based research Research Unit operated RPG Humpro profiling radiometer. This unit retrieved humidity profiles in addition to the liquid water paths and integrated water vapour paths using brightness temperatures measured at seven microwave frequencies between 22.24 and 31.4 GHz (this band in general being sensitive to water vapour and cloud). The liquid and vapour water path retrievals used a supplied neural network algorithm (which is trained with radiosonde data using a radiative transfer scheme). Two archived files are available, based on the time series (water vapour and liquid water) and profile (humidity) data.