Observationally derived transport diagnostics for the lowermost stratosphere and their application to the GMI chemistry and transport model

S. E. Strahan (1) , B. N. Duncan (1) , P. Hoor (2)

1 GEST - Goddard Earth Sciences and Technology Center
2 MPIC - Max Planck Institute for Chemistry

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, O₃, N₂O, and CO₂ 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 N₂O and O₃ 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.

Domaines: Océan, Atmosphère

S. E. Strahan, B. N. Duncan, P. Hoor. Observationally derived transport diagnostics for the lowermost stratosphere and their application to the GMI chemistry and transport model. Atmospheric Chemistry and Physics Discussions, 2007, 7 (1), pp.1449-1477. ⟨hal-00302553⟩