Profiling atmospheric water vapor with a K-band spectral radiometer

The vertical resolution of water vapor profiles from ground-based radiance measurements near the 22.235-GHz absorption line is analyzed. An informatio n content analysis identifies four frequency channels that optimally resolv e all of the linearly independent information available within this portion of the microwave spectrum for the retrieval of tropospheric water vapor by a K-band spectral radiometer (KSR) system. This instrument consists of 18 receivers operating at frequencies from 16-37 GHz, with spectral resolution s ranging from 50 MHz to 1 GHz, Parallel measurement of 18 atmospheric brig htness temperatures allows for high temporal resolution of both integrated and profiled water vapor dynamics. Inversion of the radiance spectrum is ac complished using a minimum variance estimation technique that is analyzed f or its resolution and error properties. Water vapor profiles derived from r adiometric observations made by the KSR system are presented and shown to b e in good agreement with coincident radiosonde measurements and Lidar retri evals.