Journal Article

PreJuSER-6242

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Composition of the TTL over Darwin: local mixing or long-range transport?

Heyes, W. J. ; Vaughan, G. ; Allen, G. ; Volz-Thomas, A.FZJ* ; Pätz, H.-W.FZJ* ; Busen, R.

2009
EGU Katlenburg-Lindau

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Please use a persistent id in citations: http://hdl.handle.net/2128/10129  doi:10.5194/acp-9-7725-2009

Abstract: We present ozone and carbon monoxide measurements taken in Darwin, Australia, during the wet season of 2005/2006, to examine whether the composition of the Tropical Tropopause Layer (TTL) reflects that of the local boundary layer or is influenced more by advection from distant sources. We find that the latter predominates in the upper TTL, and is also the major influence in the lower TTL, except during an active monsoon phase. The day-to-day variability of ozone in the TTL is far greater than that in the lower troposphere, and correlates closely with air mass origin deduced from trajectory calculations based on standard ECMWF wind analyses. Although clear evidence of recent local uplift was found in carbon monoxide tracer measurements recorded inside convective anvils, no such signal was found out-of-cloud in the background TTL, where the measured variability correlated well with air mass origin deduced from back-trajectories. This study suggests that the composition of the TTL is ultimately determined by vertical mixing in certain "hot spot" regions of the tropics, with advection from these regions dominating the composition elsewhere.

Keyword(s): J

Note: We thank the pilots and ground crew of the Egrett and Dornier aircraft for ensuring a successful campaign, and to Peter May and the staff of the Bureau of Meteorology (BoM) Regional Centre in Darwin for their support in forecasting and logistics. We thank also the staff of the BoM radiosonde station, Darwin, for their support of the ozonesonde programme, Marcel Berg and Norbert Houben for maintenance of the CO instrument, and the Royal Australian Air Force for hosting the aircraft experiment. Finally, we thank the UK Natural Environment Research Council (Grant NE/C512688/1) and NERC Airborne Remote Sensing Facility for supporting ACTIVE. WH is a NERC-supported research student.

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Research Program(s):

1. Atmosphäre und Klima (P22)

Appears in the scientific report 2009

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