MEASUREMENT OF THE ISOTOPIC RATIO DISTRIBUTION OF (HDO)-O-16 AND (H2O)-O-16 IN THE 20-38 KM ALTITUDE RANGE FROM FAR-INFRARED SPECTRA

The altitude distribution of the isotopic ratio between (HDO)-O-16 and (H2O)-O-16 in the stratosphere is derived by retrieving the mixing ra tio profiles (from 20 km to 38 km of altitude) of the two isotopic spe cies from far-infrared emission spectra. The measurements were made wi th a balloon-borne Fourier Transform Spectrometer capable of 0.0025 cm (-1) spectral resolution during the IBEX 92 campaign. The retrievals w ere carried out using the global-fit procedure on a statistically sign ificant number of spectra for each isotope, in the 40-75 cm(-1) spectr al region. This measurement determines the D/H ratio in stratospheric water over an altitude range larger than that of previous measurements . The value of the (HDO)-O-16/(H2O)-O-16 ratio, normalized to the stan dard value, ranges from 0.4 to 0.5 (with a 10% random error) in the al titude range studied and is in good agreement with the values previous ly measured.