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Stable water isotopologue ratios in fog and cloud droplets of liquid clouds are not size-dependent

Authors :
J. K. Spiegel
F. Aemisegger
M. Scholl
F. G. Wienhold
J. L. Collett Jr.
T. Lee
D. van Pinxteren
S. Mertes
A. Tilgner
H. Herrmann
R. A. Werner
N. Buchmann
W. Eugster
Source :
Atmospheric Chemistry and Physics, Vol 12, Iss 20, Pp 9855-9863 (2012)
Publication Year :
2012
Publisher :
Copernicus Publications, 2012.

Abstract

In this work, we present the first observations of stable water isotopologue ratios in cloud droplets of different sizes collected simultaneously. We address the question whether the isotope ratio of droplets in a liquid cloud varies as a function of droplet size. Samples were collected from a ground intercepted cloud (= fog) during the Hill Cap Cloud Thuringia 2010 campaign (HCCT-2010) using a three-stage Caltech Active Strand Cloud water Collector (CASCC). An instrument test revealed that no artificial isotopic fractionation occurs during sample collection with the CASCC. Furthermore, we could experimentally confirm the hypothesis that the δ values of cloud droplets of the relevant droplet sizes (μm-range) were not significantly different and thus can be assumed to be in isotopic equilibrium immediately with the surrounding water vapor. However, during the dissolution period of the cloud, when the supersaturation inside the cloud decreased and the cloud began to clear, differences in isotope ratios of the different droplet sizes tended to be larger. This is likely to result from the cloud's heterogeneity, implying that larger and smaller cloud droplets have been collected at different moments in time, delivering isotope ratios from different collection times.

Subjects

Subjects :
Physics
QC1-999
Chemistry
QD1-999

Details

Language :
English
ISSN :
16807316 and 16807324
Volume :
12
Issue :
20
Database :
Directory of Open Access Journals
Journal :
Atmospheric Chemistry and Physics
Publication Type :
Academic Journal
Accession number :
edsdoj.855b8a8bb340dea82045256c7a0428
Document Type :
article
Full Text :
https://doi.org/10.5194/acp-12-9855-2012