Millimeter-Wave Radiometer for High Sensitivity Water Vapor Profiling in Arid Regions

70581 Commercially-available, ground-based microwave radiometers have difficulty profiling atmospheric water vapor in arid environments. Most of these radiometers measure radiation near the 22 GHz water vapor absorption line, which has weak sensitivity to water vapor. More sensitive vapor measurements, necessary in arid regions, could be accomplished by measuring blackbody radiation near the 183 GHz absorption line. Recent technology developments allow for the design of affordable operational instruments at these millimeter wave frequencies. Therefore, this project will develop a novel 183 GHz radiometer for profiling low levels of atmospheric water vapor in dry, artic regions. The instrument combines a novel multi-channel radiometer design with a software-based, temperature-drift-compensation algorithm to achieve a high level of instrument accuracy. Phase I will build a brass-board prototype radiometer to test system sensitivity and stability, and to evaluate existing post-processing algorithms intended to compensate for residual temperature drifts. Also, a neural network-based water vapor retrieval algorithm will be developed for use in designing the optimal instrument configuration and to provide water vapor profiles in a fielded system. An affordable water vapor profiling radiometer suitable for use in dry environments, such as arctic or desert regions, will be built in Phase II. Commercial Applications and Other Benefits as described by the awardee: Specific customers should include owners and operators of research and operational weather stations and telescope sites. In addition, small, low cost, airborne-mounted water vapor radiometers could be mounted on platforms of opportunity such as commercial airlines, which could improve the forecasting of severe weather events, flash floods, and winter storms.