Establishing Lagrangian connections between observations within air masses crossing the Atlantic during the International Consortium for Atmospheric Research on Transport and Transformation experiment

J. Methven (1) , S. R. Arnold (2) , A. Stohl (3) , M. J. Evans (2) , M. Avery (4) , Kathy S. Law (5) , A. C. Lewis (6) , P. S. Monks (7) , D. D. Parrish (8) , C. E. Reeves (9) , H. Schlager (10) , E. Atlas (11) , D. R. Blake (12) , H. Coe (13) , J. Crosier (13) , F. M. Flocke (14) , J. S. Holloway (8) , J. R. Hopkins (6) , J. Mcquaid (2) , R. Purvis (15) , B. Rappenglück (16) , H. B. Singh (17) , N. M. Watson (6) , L. K. Whalley (18) , P. I. Williams (13)

1 Department of Meteorology [Reading]
2 SEE - School of Earth and Environment [Leeds]
3 NILU - Norwegian Institute for Air Research
4 LaRC - NASA Langley Research Center [Hampton]
5 SA - Service d'aéronomie
6 Department of Chemistry [York, UK]
7 Department of Chemistry [Leicester]
8 ESRL - NOAA Earth System Research Laboratory
9 School of Environmental Sciences [Norwich]
10 DLR - Deutsches Zentrum für Luft- und Raumfahrt [Oberpfaffenhofen-Wessling]
11 RSMAS - Rosenstiel School of Marine and Atmospheric Science
12 Department of Chemistry [Irvine]
13 SEAES - School of Earth, Atmospheric and Environmental Sciences [Manchester]
14 Atmospheric Chemistry Division [Boulder]
15 FAAM - Facility for Airborne Atmospheric Measurements ([Cranfield]
16 IMK-IFU - Institut für Meteorologie und Klimaforschung - Atmosphärische Umweltforschung
17 ARC - NASA Ames Research Center
18 School of Chemistry [Leeds]

The ITCT-Lagrangian-2K4 (Intercontinental Transport and Chemical Transformation) experiment was conceived with an aim to quantify the effects of photochemistry and mixing on the transformation of air masses in the free troposphere away from emissions. To this end, attempts were made to intercept and sample air masses several times during their journey across the North Atlantic using four aircraft based in New Hampshire (USA), Faial (Azores) and Creil (France). This article begins by describing forecasts from two Lagrangian models that were used to direct the aircraft into target air masses. A novel technique then identifies Lagrangian matches between flight segments. Two independent searches are conducted: for Lagrangian model matches and for pairs of whole air samples with matching hydrocarbon fingerprints. The information is filtered further by searching for matching hydrocarbon samples that are linked by matching trajectories. The quality of these “coincident matches” is assessed using temperature, humidity and tracer observations. The technique pulls out five clear Lagrangian cases covering a variety of situations and these are examined in detail. The matching trajectories and hydrocarbon fingerprints are shown, and the downwind minus upwind differences in tracers are discussed.

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]

J. Methven, S. R. Arnold, A. Stohl, M. J. Evans, M. Avery, et al.. Establishing Lagrangian connections between observations within air masses crossing the Atlantic during the International Consortium for Atmospheric Research on Transport and Transformation experiment. Journal of Geophysical Research: Atmospheres, 2006, 111 (D23), pp.D23S62. ⟨10.1029/2006JD007540⟩. ⟨hal-00144993⟩