Global water vapour distribution in the upper troposphere and lower stratosphere during CRISTA 2

Water vapour measurements during the second mission of the CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) instrument are presented in the altitude regime 8–20 km. Mixing ratios are shown on isentropic surfaces (300–500 K) as global zonal means and as averages in 60° longitude sectors. Transports are indicated to occur preferentially on isentropic surfaces in the northern hemisphere, but not in the tropics and in the south. The hygropause is found shifted away from the equator towards the winter hemisphere. The amount of shift is longitude dependent and can be as great as 20–30°. The water content of the hygropause area shows considerable zonal asymmetries.