Journal Article

FZJ-2014-04934

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Departure from Clausius- Clapeyron scaling of water entering the stratosphere in response to changes in tropical upwelling

Fueglistaler, S. (Corresponding Author) ; Liu, Y. S. ; Flannaghan, T. J. ; Ploeger, F.FZJ* ; Haynes, P. H.

2014
Union Washington, DC

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Please use a persistent id in citations: http://hdl.handle.net/2128/16095  doi:10.1002/2013JD020772

Abstract: Water entering the stratosphere ([H2O]entry) is strongly constrained by temperatures in the tropical tropopause layer (TTL). Temperatures at tropical tropopause levels are 15–20 K below radiative equilibrium. A strengthening of the residual circulation as suggested by general circulation models in response to increasing greenhouse gases is, based on radiative transfer calculations, estimated to lead to a temperature decrease of about 2 K per 10% change in upwelling (with some sensitivity to vertical scale length). For a uniform temperature change in the inner tropics, [H2O]entry may be expected to change as predicted by the temperature dependence of the vapor pressure, referred here as “Clausius-Clapeyron (CC) scaling.” Under CC scaling, this corresponds to ∼1 ppmv change in [H2O]entry per 10% change in upwelling. However, the change in upwelling also changes the residence time of air in the TTL. We show with trajectory calculations that this affects [H2O]entry, such that [H2O]entry changes ∼10 % less than expected from CC scaling. This residence time effect for water vapor is a consequence of the spatiotemporal variance in the temperature field. We show that for the present-day TTL, a little more than half of the effect is due to the systematic relation between flow and temperature field. The remainder can be understood from the perspective of a random walk problem, with slower ascent (longer path) increasing each air parcel's probability to encounter anomalously low temperatures. Our results show that atmospheric water vapor may depart from CC scaling with mean temperatures even when all physical processes of dehydration remain unchanged.

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Contributing Institute(s):

1. Stratosphäre (IEK-7)

Research Program(s):

1. 234 - Composition and Dynamics of the Upper Troposphere and Stratosphere (POF2-234) (POF2-234)

Appears in the scientific report 2014

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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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