Vertical distribution of deuterium in atmospheric water vapour: problems in application to assess atmospheric condensation models

Abstract

The paper assesses the use of the author’s data by Rozanski and Sonntag to support a multi-boxmodel of the vertical distribution of deuterium in atmospheric water vapour, in which exchangebetween vapour and falling precipitation produces a steeper deuterium concentration profile thansimpler condensation models. The mean deuterium/altitude profile adopted by Rozanski andSonntag for this purpose is only one of several very different mean profiles obtainable from thedata by arbitrary selection and weighting procedures: although it can be made to match :hespecified multi-box model calculations for deuterium. there is a wide discrepancy between theactual and model mean mixing ratio profiles which cannot be ignored. Taken together. the mixingratio and deuterium profiles indicate that mean vapour of the middle troposphere has beensubjected to condensation at greater heights and lower temperatures than those considered in themodel calculations. When this is taken into account, the data actually fit much better to thesimpler condensation models. But the vapour samples represent meteorological situations tooremote in time from primary precipitation events to permit definite conclusions on cloud systemmechanisms.