Open AccessStratosphere‐troposphere exchange: Inferences from the isotopic composition of water vapor
Author(s) -
Keith David W.
Publication year - 2000
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2000jd900130
Subject(s) - stratosphere , tropopause , water vapor , troposphere , atmospheric sciences , cirrus , environmental science , climatology , mixing ratio , relative humidity , convection , evaporation , lapse rate , meteorology , geology , physics
Air may cross the tropical tropopause either by gradual ascent or in localized episodes associated with convection. While observations demonstrate that water vapor mixing ratios of air entering the tropical stratosphere are consistent with the mean tropical tropopause temperature, they do not resolve key mechanistic questions, such as the relative contribution of gradual or episodic transport, or the role of thin cirrus. As Moyer et al . [1996] clearly argue, observations of the isotopic content of water entering the tropical stratosphere can provide a strong constraint on models of water vapor transport across the tropopause. For example, stratospheric HDO is too abundant to be compatible with the assumption that all moisture enters the stratosphere as vapor during convection. Analysis of recent H 2 18 O observations shows that kinetic effects cannot explain the HDO excess. Lofting and evaporation of cloud ice can explain the observed stratospheric water vapor content and its isotopic composition, but the relative importance of gradual or episodic transport remains unresolved.