Atmospheric Chemistry and Physics Discussions
www.atmos-chem-phys-discuss.net
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7
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2007
10.5194/acpd-7-8597-2007
http://www.atmos-chem-phys-discuss.net/7/8597/2007/
http://www.atmos-chem-phys-discuss.net/7/8597/2007/acpd-7-8597-2007.html
http://www.atmos-chem-phys-discuss.net/7/8597/2007/acpd-7-8597-2007.pdf
8597
8616
2007-06-21
Transport and modeling of stratospheric inorganic chlorine
D. W. Waugh
waugh@jhu.edu
S. E. Strahan
P. A. Newman
Department of Earth and Planetary Science, Johns Hopkins University, MD, USA
University of Maryland Baltimore County, Goddard Earth Sciences and Technology Center, MD, USA
NASA Goddard Space Flight Center, Greenbelt, MD, USA
Correctly modeling stratospheric inorganic chlorine (Cl<sub>y</sub>) is
crucial for modeling the past and future evolution of stratospheric
ozone. However, comparisons of the chemistry climate models used in
the latest international assessment of stratospheric ozone depletion
have shown large differences in the modeled Cl<sub>y</sub>, with these
differences explaining differences in the simulated evolution of
ozone over the next century. Here in, we examine the role of
transport in determining the simulated Cl<sub>y</sub> using three simulations
from the same off-line chemical transport model that have the same
lower tropospheric boundary conditions and the same chemical solver,
but differing resolution and/or meteorological fields. These
simulations show that transport plays a key role in determining the
Cl<sub>y</sub> distribution, and that Cl<sub>y</sub> depends on both the time scales
and pathways of transport. The time air spends in the stratosphere
(e.g., the mean age) is an important transport factor determining
stratospheric Cl<sub>y</sub>, but the relationship between mean age and Cl<sub>y</sub>
is not simple. Lower stratospheric Cl<sub>y</sub> depends on the fraction of
air that has been in the upper stratosphere, and transport
differences between models having the same mean age can result in
differences in the fraction of organic chlorine converted into
Cl<sub>y</sub>. Differences in transport pathways result in differences in
vertical profiles of CFCs, and comparisons of observed and modeled
CFC profiles provides a stringent test of transport pathways in
models.
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