Ground-based microwave radiometer measurements and radiosonde comparisons during the WVIOP2000 field experiment

We discuss the performances of a set of four microwave radiometers during a field experiment, with an emphasis on calibration and achievable accuracy. A comparison between two alternative tip curve calibration procedures has been carried out. Additional results from reference load cryogenic tests and from brightness temperature cross-comparison are shown. Also, we compare radiometric measurements with radiosonde observations and we demonstrate the improvements achieved by the new Vaisala sensors to reduce or eliminate the "dry bias" problem.