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GEOPHYSICAL RESEARCH LETTERS,
VOL. 32,
L01808,
doi:10.1029/2004GL021125,
2005
Implications of persistent ice supersaturation in cold cirrus for stratospheric water vapor
E. Jensen
NASA Ames Research Center, Moffett Field, California, USA
L. Pfister
NASA Ames Research Center, Moffett Field, California, USA
Abstract
Recent measurements made near the tropical tropopause during the NASA Cirrus Regional Study of Tropical Anvils and Cirrus
Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE) indicate persistent ice saturation ratios (s
i
) of about 1.2–1.3 in cold ice clouds (T < 200 K) even when the ice surface area is substantial [
Gao et al., 2004
]. These observations challenge the conventional thinking that any water vapor in excess of ice saturation should be depleted
by crystal growth given sufficient time. Here we use model simulations to evaluate the impact of this steady-state ice supersaturation
on cirrus formed in situ within the tropical tropopause layer and water vapor fluxes across the tropical tropopause. We show
that cirrus occurrence frequencies are unexpectedly increased, and we estimate an increase of about 0.5–1 ppmv in the water
vapor concentration in air entering the stratosphere. Inclusion of the enhanced in-cloud supersaturation in our simulations
improves agreement with satellite measurements of water vapor.
Received 28
July
2004;
accepted 2
December
2004;
published 13
January
2005.
Index Terms: 0320 Atmospheric Composition and Structure: Cloud physics and chemistry; 0340 Atmospheric Composition and Structure: Middle atmosphere: composition and chemistry; 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry.
Read Full Article (file size: 1006572 bytes) Cited by
Citation: Jensen, E., and L. Pfister
(2005),
Implications of persistent ice supersaturation in cold cirrus for stratospheric water vapor,
Geophys. Res. Lett.,
32,
L01808,
doi:10.1029/2004GL021125.
This paper is not subject to U.S. copyright. Published in 2005 by the
American Geophysical Union.
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