Chemical and dynamical discontinuity at the extratropical tropopause based on STRT08 and WACCM analyses

Kunz, A.; Pan, L.L.; Konopka, P.; Kinnison, D.E.; Tilmes, S.

doi:10.1029/2011JD016686

Journal Article

PreJuSER-17224

Chemical and dynamical discontinuity at the extratropical tropopause based on STRT08 and WACCM analyses

Kunz, A.FZJ* ; Pan, L. L. ; Konopka, P.FZJ* ; Kinnison, D. E. ; Tilmes, S.

2011
Union Washington, DC

Journal of Geophysical Research 116, (2011) [10.1029/2011JD016686]

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Please use a persistent id in citations: http://hdl.handle.net/2128/20916 doi:10.1029/2011JD016686

Abstract: Using isentropic trace gas gradients of O-3 and CO, the discontinuity in the chemical composition of the upper troposphere (UT) and lower stratosphere (LS) is examined on middle world isentropes from 300 to 380 K. The analysis is a follow-up study of the dynamical discontinuity as represented by the potential vorticity (PV) gradient-based tropopause, which is based on the product of isentropic PV gradients and wind speed. Overall, there is fairly good consistency between the chemical discontinuity in trace gas distributions and the PV gradient-based tropopause. Trace gas gradients at the PV gradient-based tropopause are stronger in winter than in summer, revealing the seasonal cycle of the tropopause transport barrier. The analysis of the trace gas gradients also identifies atmospheric transport pathways in the upper troposphere-lower stratosphere (UTLS). Several regions where trace gas gradients are found to be decoupled from the dynamical field indicate preferred transport pathways between the UT and LS. In particular, anomalous CO and O-3 gradients above eastern Africa, eastern Asia, and the West Pacific are likely related to convective transport, and anomalous O-3 gradients over the North Atlantic and North Pacific are related to isentropic transport connected to frequent wave breaking. The results indicate that the PV gradient-based tropopause definition provides a good identification of the dynamical and chemical discontinuity and is therefore effective in locating the physical boundary in the UTLS.

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Meteorology & Atmospheric Sciences

Note: A. Kunz is supported by the German Academy of Sciences Leopoldina (LPDS 2009-25) and the visitor's program of the Atmospheric Chemistry Division at the National Center for Atmospheric Research (NCAR). NCAR is funded by the National Science Foundation. Fruitful discussions with Rolf Muller, Thomas Birner, and Tanya Peevey during the progress of this work are particularly acknowledged. Thanks to Heini Wemli and to two anonymous reviewers for their helpful comments.

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