Vertical distribution of deuterium in atmospheric water vapour

Abstract

Available experimental data on the vertical deuterium distribution in atmospheric water vapour show a steep decrease of deuterium with altitude in the lower troposphere. Condensation removal of water alone does not correctly reproduce the isotopic evolution of ascending air masses and the steep deuterium profiles observed. Therefore, a multibox cloud model is proposed to explain the experimental data. In this one-dimensional model a complete isotope exchange between the falling raindrops and the vapour and cloud water at various atmospheric levels is proposed.

The observed deuterium increase near the tropopause is proposed to be at least partly due to downward mixing of isotopically heavy water vapour produced by methane decomposition in the upper atmosphere.