Optical balloon hygrometer for upper-troposphere and stratosphere water vapor measurements

Abstract

An optical hygrometer has been upgraded to make night-time measurements of water vapor in the upper troposphere and stratosphere using the technique of photofragment fluorescence. Hygrometer uses the fluorescence at wavelength near 310 nm of excited OH molecules produced in the photodissociation of water molecules by UV radiation with hydrogen lamp. A coaxial optical scheme and photon counting mode are 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. Total weight of the optical hygrometer is about 2 kg. It can be easily integrated with the Vaisala RS-80 radiosonde. This allows to obtain reliable real-time data on temperature, pressure and water vapor concentration in the upper troposphere and stratosphere and conduct the validation of the remote sensing data.