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| Titel |
Transport of short-lived species into the Tropical Tropopause Layer |
| VerfasserIn |
M. J. Ashfold, N. R. P. Harris, E. L. Atlas, A. J. Manning, J. A. Pyle |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 14 ; Nr. 12, no. 14 (2012-07-19), S.6309-6322 |
| Datensatznummer |
250011329
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| Publikation (Nr.) |
 copernicus.org/acp-12-6309-2012.pdf |
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| Zusammenfassung |
| We use NAME, a trajectory model, to investigate the routes and timescales
over which air parcels reach the tropical tropopause layer (TTL). Our aim is
to assist the planning of aircraft campaigns focussed on improving knowledge
of such transport. We focus on Southeast Asia and the Western Pacific which
appears to be a particularly important source of air that enters the TTL. We
first study the TTL above Borneo in November 2008, under neutral El
Niño/Southern Oscillation (ENSO) conditions. Air parcels (trajectories)
arriving in the lower TTL (below ~15 km) are most likely to have
travelled from the boundary layer (BL; <1 km) above the West Pacific. Few
air parcels found above ~16 km travelled from the BL in the previous
15 days. We then perform similar calculations for moderate El Niño (2006)
and La Niña (2007) conditions and find year-to-year variability
consistent with the phase of ENSO. Under El Niño conditions fewer air
parcels travel from the BL to the TTL above Borneo. During the La Niña
year, more air parcels travel from the BL to the mid and upper TTL (above
~15 km) than in the ENSO-neutral year, and again they do so from the BL
above the West Pacific. We also find intra-month variability in all years,
with day-to-day differences of up to an order of magnitude in the fraction of
an idealised short-lived tracer travelling from the BL to the TTL above
Borneo. These calculations were performed as a prelude to the SHIVA field
campaign, which took place in Borneo during November 2011. So finally, to
validate our approach, we consider measurements made in two previous
campaigns. The features of vertical profiles of short-lived species observed
in the TTL during CR-AVE and TC4 are in broad agreement with calculated
vertical profiles of idealised short-lived tracers. It will require large
numbers of observations to fully describe the statistical distribution of
short-lived species in the TTL. This modelling approach should prove valuable
in planning flights for the long-duration aircraft now capable of making such
measurements. |
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