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Transport Between the Tropical and Midlatitude Lower Statosphere: Implications for Ozone Response to High-Speed Civil Transport EmissionsSeveral recent studies have quantified the air exchange rate between the tropics and midlatitudes in the lower stratosphere using airborne and satellite measurements of chemical species. It is found that the midlatitude air is mixed into the tropical lower stratosphere with a replacement timescale of 13.5 months (with 20% uncertainty) for the region from the tropopause to 21 km and at least 18 months for the region of 20-28 km. These estimates are used to adjust the horizontal eddy diffusion coefficients, K(sub yy), in a two-dimensional chemistry transport model. The value of K(sub yy) previously used to simulate the subtropical barrier, 0.03 x 10(exp 6) sq m/s, generates an exchange time of about 4 years, and the model without subtropical barrier (K(sub yy) = 0.3 x 10(exp 6) sq m/s) has an exchange time of 5 months. Adjusting the K(sub yy) to 0.13 x 10(exp 6) sq m/s from the tropopause to 21 km and 0.07 x 10(exp 6) sq m/s above 21 km produces the exchange timescales which match the estimates deduced from the measurements. The subtropical barrier prevents the engine emissions of the high-speed civil transport (HSCT) aircraft from being transported into the tropics and subsequently lifted into the upper atmosphere or mixed into the southern hemisphere. The model results show that the calculated ozone response to HSCT aircraft emissions using the K(sob yy) adjusted to observed mixing rates is substantially smaller than that simulated without the subtropical barrier.
Document ID
20000011669
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Shia, R.-L.
(Atmospheric and Environmental Research, Inc. Cambridge, MA United States)
Ko, M. K. W.
(Atmospheric and Environmental Research, Inc. Cambridge, MA United States)
Weisenstein, D. K.
(Atmospheric and Environmental Research, Inc. Cambridge, MA United States)
Scott, C.
(Atmospheric and Environmental Research, Inc. Cambridge, MA United States)
Rodriguez, J.
(Atmospheric and Environmental Research, Inc. Cambridge, MA United States)
Date Acquired
August 19, 2013
Publication Date
October 20, 1998
Publication Information
Publication: Journal of Geophysical Research
Publisher: American Geophysical Union
Volume: 103
Issue: D19
ISSN: 0148-0227
Subject Category
Geophysics
Report/Patent Number
Paper-98JD01882
Funding Number(s)
CONTRACT_GRANT: NAS5-32371
CONTRACT_GRANT: NAS5-97039
Distribution Limits
Public
Copyright
Other

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