Combining UHF radar wind profiler and microwave radiometer for the estimation of atmospheric humidity profiles

Capabilities of an integrated ground-based system for the operational measurement of humidity profiles, using both an UHF wind profiler and a radiometer, are discussed. The combination takes advantage of the complementary characteristics of each instrument. The radiometer is able to give a fair evaluation of smoothed humidity and temperature profiles, while the wind profiler is more suited for gradient estimations between range gates. Measurements of high-resolution humidity profiles in the combined sensor approach are based on the calculation of the refractive index gradients from the radar return signal power and signal width. Various means are then tested to combine these measurements with the radiometric data in order to deduce the most accurate humidity profile. This study is performed on 51 cases of UHF profiles during which 37 radiometric measurements were available. They have been selected on a data set collected during the international COST 720 Temperature, hUmidity and Cloud (TUC) profiling experiment held in Payerne (CH). During the experiment a LAP-3000 wind profiling radar and a Radiometrics temperature and humidity profiling radiometer operated simultaneously with Swiss radiosonde SRS 400.