Journal Article

PreJuSER-17546

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Horizontal transport affecting trace gas seasonality in the Tropical Tropopause Layer (TTL)

Plöger, F.FZJ* ; Konopka, P.FZJ* ; Müller, R.FZJ* ; Fueglistaler, S. ; Schmidt, T. ; Manners, J. C. ; Grooß, J.-U.FZJ* ; Günther, G.FZJ* ; Riese, M.FZJ*

2012
Union Washington, DC

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Please use a persistent id in citations: http://hdl.handle.net/2128/20646  doi:10.1029/2011JD017267

Abstract: We analyze horizontal transport from midlatitudes into the tropics (in-mixing) and its impact on seasonal variations of ozone, carbon monoxide and water vapor in the Tropical Tropopause Layer (TTL). For this purpose, we use three-dimensional backward trajectories, driven by ECMWF ERA-Interim winds, and a conceptual one-dimensional model of the chemical composition of the TTL. We find that the fraction of in-mixed midlatitude air shows an annual cycle with maximum during NH summer, resulting from the superposition of two inversely phased annual cycles for in-mixing from the NH and SH, respectively. In-mixing is driven by the monsoonal upper-level anticyclonic circulations. This circulation pattern is dominated by the Southeast Asian summer monsoon and, correspondingly, in-mixing shows an annual cycle. The impact of in-mixing on TTL mixing ratios depends on the in-mixed fraction of midlatitude air and on the meridional gradient of the particular species. For CO the meridional gradient and consequently the effect of in-mixing is weak. For water vapor, in-mixing effects are negligible. For ozone, the meridional gradient is large and the contribution of in-mixing to the ozone maximum during NH summer is about 50%. This in-mixing contribution is not sensitive to the tropical ascent velocity, which is about 40% too fast in ERA-Interim. As photochemically produced ozone in the TTL shows no distinct summer maximum, the ozone annual anomaly in the upper TTL turns out to be mainly forced by in-mixing of ozone-rich extratropical air during NH summer.

Keyword(s): J

Note: We thank M. Volk and Bill Randel for helpful discussions and the ECMWF for providing the reanalysis data. F. Ploeger thanks COST for funding a Short Term Scientific Mission at DAMTP/Cambridge.

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Contributing Institute(s):

1. Stratosphäre (IEK-7)

Research Program(s):

1. Atmosphäre und Klima (P23)

Appears in the scientific report 2012

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Database coverage:
; ; Current Contents - Agriculture, Biology and Environmental Sciences ; Current Contents - Social and Behavioral Sciences ; JCR ; NCBI Molecular Biology Database ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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