Optical fluorescent hygrometer for water vapor low concentration measurements

摘要

Abstract: An optical hygrometer has been developed to make night-time measurements of water vapor in the upper atmosphere using the technique of photofragment fluorescence. Hygrometer uses the fluoroscence at wavelengths near 310 nm of excited OH molecules produced in the photodissociation of water molecules by UV radiation with hydrogen lamp (121.6 nm). A coaxial optical scheme is used. A compact hydrogen lamp is aligned along the axis of the instrument, inside the annular fast focusing optics. It provides the effective convergence of fluorescence from a large angle and thus increase the sensitivity of this method. The modulation of the hydrogen lamp with the frequency 1 kHz is used. Specially designed laboratory technique for calibration of the hygrometer is described. Total weight of the optical hygrometer is about 3 kg. It can be easily integrated with the Vaisala RS-80 radio sonde. This allows us to obtain reliable real-time data on temperature, pressure, and water vapor concentrations in the upper troposphere and stratosphere. !16