edu.ucar.opensky::articles:6508 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T15:29:57.043279 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7h70g1f Variability in HDO/H₂O abundance ratios in the tropical tropopause layer 2007-11-06T00:00:00Z publication https://n2t.org/ark:/85065/d7h70g1f https://doi.org/10.1029/2007JD008417 Nassar, R. author Bernath, P. author Boone, C. author Gettelman, Andrew author McLeod, S. author Rinsland, C. author UCAR/NCAR - Library publisher The dehydration of air in the tropical tropopause layer (TTL) and mechanisms for the entry of water vapor into the stratosphere are investigated by an analysis of ACE-FTS profiles of temperature, water vapor, and the ratio [HDO]/[H₂O] expressed in δD notation. Month-to-month comparisons indicate greater seasonal variability than interannual variability between 25°S - 25°N, thus comparisons are made between February, April, August, and October averages for the years 2004 and 2005 combined. The data indicate a pattern of seasonal variability which is clearer in the Northern Hemisphere tropics and a relationship between minimum temperature, minimum water vapor, and maximum HDO depletion, which exists beyond the estimated uncertainty in these values. The range of values observed for HDO depletion and comparisons to modeled Rayleigh distillation curves indicate an important contribution from convection in addition to gradual dehydration. Multiple factors including the shape of the δD profiles suggest that a likely mechanism for the convective influence is the lofting of ice particles in the tropical troposphere. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication An edited version of this paper was published by AGU. Copyright 2007 American Geophysical Union. None eng geoscientificInformation