Calibration and intercomparison of water vapor instrumentation used on the NSF/NCAR HIAPER aircraft

Subject of the study is the characterization of a Kahn DCS-80 water vapor calibration system and the calibration of two water vapor sensors used on research aircraft, namely a Buck Instruments B-1001 chilled mirror sensor and a MayComm Tunable Diode Laser Absorption Hygrometer. A series of Vaisala drop sondes were also characterized and compared to the aircraft instruments. In an effort to assess the precision of the water vapor sensors that are being used on board the NSF/NACR GV aircraft (HIAPER), the instruments were tested at ambient pressure (800 mbar) inside an environmental chamber to simulate temperature conditions during flight. Tested dewpoints ranged from -70 to +20 degrees Celsius. The TDL - hygrometer was calibrated in preparation for an international water vapor measurement intercomparison campaign at the Forschungszentrum Karlsruhe, Germany. We will present the detailed calibration and characterization procedure, the laboratory setup for the different sensors, results from the calibrations of all instruments, assess their precision and useful operating range, and present some preliminary results from the international intercomparison campaign.