Water vapouR ANalyzer (WARAN): compact airborne hygrometer for the upper troposphere

Abstract

Numerical weather prediction and climate models require a broad set of atmospheric measurement data to stick close to reality. While important meteorological data like e.g. emperature are provided by commercial aircraft connected to the AMDAR network (Aircraft Meteorological DAta Relay), humidity data of the upper troposphere are rare. In order to evaluate the suitability of humidity sensors to be integrated in the AMDAR network, we tested the WARAN (WAter vapoR ANalyzer) tuneable diode laser (TDL) hygrometer (WVSS-II from Spectrasensors Inc.) in the laboratory and on the Falcon 20E research aircraft with a Rosemount inlet system. Atmospheric water vapour measurements with the WARAN on the Falcon covering a range from less than 20 to 20000 ppmv are compared to the aircraft meteorological instrumentation. In addition, we show results from an intercomparison to humidity data with the LIDAR (light detection and ranging) instrument onboard the new German research aircraft HALO. In particular, we investigate the humidity in cirrus clouds and in cloud free conditions. The results suggest that the WARAN can provide reliable humidity data from ground level up to the upper troposphere.