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

70581S02-II Current microwave water vapor radiometers lack sufficient sensitivity to measure atmospheric water vapor in the Arctic and other arid climates. Therefore, this project will develop a remotely operable, multi-channel radiometer designed specifically for the measurement of atmospheric water vapor and liquid water in arid regions. The radiometer, which will combine state-of-the-art RF design techniques with novel processing algorithms, will operate near the 183 GHz water vapor line to provide the best means for measuring low levels of atmospheric water vapor. Phase I investigated the optimal instrument configuration for measuring low levels of integrated water vapor and liquid water, as well as the ability to generate vertical profiles of water vapor. In order to estimate these quantities, an artificial neural network algorithm, trained on data from the DOE Cloud and Radiation Test (CART) site in Barrow, Alaska, was developed. This algorithm was also used to demonstrate the ability of an uncalibrated radiometer to measure these same quantities with somewhat reduced accuracy. Phase II will build two high performance radiometers for deployment at the Barrow and Atqasuk, Alaska CART sites. A compact, lower cost 183 GHz radiometer, capable of providing similar data without the need for internal calibration loads or a scanning antenna, also will be built. This latter radiometer will be validated through comparison with a microwave water vapor radiometer and tested onboard a research aircraft. Commercial Applications and Other Benefits as described by awardee: The research should result in the first commercially available, 183 GHz radiometers suitable for scientific or operational measurement of atmospheric integrated water vapor and liquid water in dry environments.