Atmospheric Chemistry and Physics Discussions
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10.5194/acpd-7-1449-2007
http://www.atmos-chem-phys-discuss.net/7/1449/2007/
http://www.atmos-chem-phys-discuss.net/7/1449/2007/acpd-7-1449-2007.html
http://www.atmos-chem-phys-discuss.net/7/1449/2007/acpd-7-1449-2007.pdf
1449
1477
2007-01-29
Observationally derived transport diagnostics for the lowermost stratosphere and their application to the GMI chemistry and transport model
S. E. Strahan
sstrahan@pop600.gsfc.nasa.gov
B. N. Duncan
P. Hoor
Goddard Earth Science and Technology Center, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
Max Planck Institute for Chemistry, Air Chemistry, Mainz, Germany
Transport from the surface to the lowermost
stratosphere can occur on timescales of a few months or less, making it
possible for short-lived tropospheric pollutants to influence stratospheric
composition and chemistry. Models used to study this influence must
demonstrate the credibility of their chemistry and transport in the upper
troposphere and lower stratosphere (UT/LS). Data sets from satellite and
aircraft instruments measuring CO, O<sub>3</sub>, N<sub>2</sub>O, and CO<sub>2</sub> in the
UT/LS are used to create a suite of diagnostics of the seasonally-varying
transport into and within the lowermost stratosphere, and of the coupling
between the troposphere and stratosphere in the extratropics. The
diagnostics are used to evaluate a version of the Global Modeling Initiative
(GMI) Chemistry and Transport Model that uses a combined tropospheric and
stratospheric chemical mechanism and meteorological fields from the GEOS-4
general circulation model. The diagnostics derived from N<sub>2</sub>O and O<sub>3</sub>
show that the model lowermost stratosphere (LMS) has realistic input from
the overlying high latitude stratosphere in all seasons. Diagnostics for the
LMS show two distinct layers. The upper layer (~350 K–380 K) has a
strong annual cycle in its composition, while the lower layer, just above
the tropopause, shows no seasonal variation in the degree of tropospheric
coupling or composition. The GMI CTM agrees closely with the observations in
both layers and is realistically coupled to the UT in all seasons. This
study demonstrates the credibility of the GMI CTM for the study of the
impact of tropospheric emissions on the stratosphere.
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