Hydration and dehydration at the tropical tropopause

Schiller, C.; Konopka, P.; Plöger, F.; Spelten, N.; Grooß, J.-U.; Silva dos Santos, F.H.

doi:10.5194/acp-9-9647-2009

Journal Article

Hydration and dehydration at the tropical tropopause

Schiller, C.FZJ* ; Grooß, J.-U.FZJ* ; Konopka, P.FZJ* ; Plöger, F.FZJ* ; Silva dos Santos, F. H. ; Spelten, N.FZJ*

2009
EGU Katlenburg-Lindau

Atmospheric chemistry and physics 9, 9647 - 9660 (2009) [10.5194/acp-9-9647-2009]

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Please use a persistent id in citations: http://hdl.handle.net/2128/10067 doi:10.5194/acp-9-9647-2009

Abstract: High-resolution water measurements from three tropical airborne missions in Northern Australia, Southern Brazil and West Africa in different seasons are analysed to study the transport and transformation of water in the tropical tropopause layer (TTL) and its impact on the stratosphere. The mean profiles are quite different according to the season and location of the campaigns, with lowest mixing ratios below 2 ppmv at the cold point tropopause during the Australian mission in November/December and high TTL mixing ratios during the African measurements in August. We present backward trajectory calculations considering freeze-drying of the air to the minimum saturation mixing ratio and initialised with climatological satellite data. This trajectory-based reconstruction of water agrees well with the observed H2O average profiles and therefore demonstrates that the water vapour set point in the TTL is primarily determined by the Lagrangian saturation history. Deep convection was found to moisten the TTL, in several events even above the cold point up to 420 K potential temperatures. However, our study does not provide evidence for a larger impact of these highly-localised events on global scales.

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Meteorology & Atmospheric Sciences

Note: Discussion of the results and developing ideas of their meaning with many members of the project teams of SCOUT-O3, TroCCiNOx and AMMA/SCOUT-O3 is gratefully acknowledged. We thank MDB, DLR and ERS-Ltd operating and managing the aircraft under the challenging tropical conditions. The study was primarily conducted under the SCOUT-O3 Integrated Project (EC Contract GOCE-CT-2004-505390), with additional campaign funding by the EC projects TroCCiNOx and AMMA as well as by INSU and the Geophysica EEIG.

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