Measurements of the isotopic composition of stratospheric water by the ATMOS instrument
are used to infer the convective history of stratospheric air. The average water vapor
entering the stratosphere is found to be highly depleted of deuterium, with δDw of− 670±80
(67% deuterium loss). Model calculations predict, however, that under conditions of
thermodynamic equilibrium, dehydration to stratospheric mixing ratios should produce
stronger depletion to δDw of− 800 to− 900 (80–90% deuterium loss). Deuterium enrichment …

The isotopic composition of stratospheric water vapor is used as a tracer for the convective
history of air injected into the stratosphere. Stratospheric profiles of HDO, H 2 O, CH 3 D, and
CH 4 fro the ATMOS instrument, obtained over four missions from 1985-1994, are used to
determine the initial deuterium-to-hydrogen ration of water vapor entering the stratosphere.
We find that the initial DeltaD of stratospheric water is-680±80 (68 percent loss of
deuterium), consistent with extrapolations from previous measurements at higher altitudes.