Vertical profiles of HDO/H2O in the troposphere -: art. no. D13301

This paper reanalyzes the measurements of the D content in tropospheric water vapor by Ehhalt ( 1974) correcting for the isotopic contamination by wall water in the sampling tubes. The resulting corrections decrease the original D content. They are small for the data from the flights through 1967, which extended from the surface to 9 km altitude, but are large for the flights beginning 1971, which ranged from 6 to 13 km altitude and collected smaller amounts of water vapor. No correction therefore was attempted for the latter. The corrected data of the earlier flights are presented in the form of seasonally averaged profiles over Scotts Bluff, Nebraska; Death Valley, California; and the Pacific offshore of San Luis Obispo, California. As to be expected, the vertical profiles from the earlier flights show a decrease in the D content with altitude and a seasonal variation at all altitudes. However, when plotted against the water vapor mixing ratio, the D data from all seasons collapse on a line which closely follows that given by Rayleigh condensation with a fractionation factor alpha = 1.1, constant with altitude. These data can be explained by a simple one-dimensional convection model and the assumption that condensed water is lofted along with the water vapor.