ACP Atmospheric Chemistry and Physics ACP Atmos. Chem. Phys. 1680-7324 Copernicus Publications Göttingen, Germany 10.5194/acp-10-2237-2010 An introduction to the SCOUT-AMMA stratospheric aircraft, balloons and sondes campaign in West Africa, August 2006: rationale and roadmap Cairo F. 1 Pommereau J. P. 2 Law K. S. 2 Schlager H. 3 Garnier A. 2 Fierli F. 1 Ern M. 4 Streibel M. 5 Arabas S. 6 Borrmann S. 8 7 Berthelier J. J. 2 Blom C. 9 Christensen T. 10 D'Amato F. 11 Di Donfrancesco G. 12 Deshler T. 13 Diedhiou A. 14 Durry G. 15 Engelsen O. 16 Goutail F. 2 Harris N. R. P. 5 Kerstel E. R. T. 17 Khaykin S. 18 Konopka P. 4 Kylling A. 16 Larsen N. 10 Lebel T. 14 Liu X. 15 MacKenzie A. R. 19 Nielsen J. 10 Oulanowski A. 18 Parker D. J. 20 Pelon J. 2 Polcher J. 21 Pyle J. A. 22 29 Ravegnani F. 1 Rivière E. D. 15 Robinson A. D. 22 Röckmann T. 23 Schiller C. 4 Simões F. 2 Stefanutti L. 24 25 Stroh F. 4 Some L. 26 Siegmund P. 27 Sitnikov N. 18 Vernier J. P. 2 Volk C. M. 28 Voigt C. 7 3 von Hobe M. 4 Viciani S. 11 Yushkov V. 18 Istituto di Scienze dell'Atmosfera e del Clima ISAC-CNR , Consiglio Nazionale delle Ricerche, Italy LATMOS, CNRS, Université de Versailles St-Quentin, Université Paris 6, France Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany ICG-1, Forschungszentrum Jülich, Jülich, Germany European Ozone Research Coordinating Unit, Cambridge University, Cambridge, UK Institute of Geophysics, University of Warsaw, Warsaw, Poland Institute of Atmospheric Physics, University of Mainz, Mainz, Germany Max-Planck Institute for Chemistry, Particle Chemistry Department, Mainz, Germany Institut für Meteorologie und Klimaforschung (IMK), Forschungszentrum Karlsruhe und Universität Karlsruhe, Karlsruhe, Germany Danish Meteorological Institute, Copenhagen, Denmark Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Firenze, Italy Ente Nazionale per le Nuove tecnologie, l'Energia e l'Ambiente, Frascati, Italy Department of Atmospheric Sciences, Wyoming University, Laramie, USA LTHE, Université J.Fourier, Institut de Recherche pour le Developpement-France, Grenoble, France Groupe de Spectroscopie Moléculaire et Atmosphérique, Faculté des Sciences, Université de Reims Champagne-Ardenne and CNRS, Reims, France Norwegian Institute for Air Research, Oslo, Norway Center for Isotope Research, University of Groningen, Groningen, The Netherlands Central Aerological Observatory, Moscow, Russia Lancaster Environmental Centre, Lancaster University, Lancaster, UK School of Earth and Environment, University of Leeds, Leeds, UK Laboratoire de Météoreologie Dynamique, CNRS, Paris, France Chemistry Department, Cambridge University, Cambridge, UK Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, The Netherlands Istituto di Ricerche per la Protezione Idrogeologica, Consiglio Nazionale delle Ricerche, Firenze, Italy Geophysica-EEIG, Firenze, Italy INERA, Ouagadougou, Burkina Faso Royal Netherlands Meteorological Institute – KNMI, The Netherlands Department of Physics, University of Wuppertal, Wuppertal, Germany National Centre for Atmospheric Science, NCAS-Climate, Cambridge, UK 03 03 2010 10 5 2237 2256 Copyright: © 2010 F. Cairo et al. 2010 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://acp.copernicus.org/articles/10/2237/2010/acp-10-2237-2010.html The full text article is available as a PDF file from https://acp.copernicus.org/articles/10/2237/2010/acp-10-2237-2010.pdf

A multi-platform field measurement campaign involving aircraft and balloons took place over West Africa between 26 July and 25 August 2006, in the frame of the concomitant AMMA Special Observing Period and SCOUT-O<sub>3</sub> African tropical activities. <br><br> Specifically aiming at sampling the upper troposphere and lower stratosphere, the high-altitude research aircraft M55 Geophysica was deployed in Ouagadougou (12.3&deg; N, 1.7&deg; W), Burkina Faso, in conjunction with the German D-20 Falcon, while a series of stratospheric balloons and sonde flights were conducted from Niamey (13.5&deg; N, 2.0&deg; E), Niger. <br><br> Altogether, these measurements were intended to provide experimental evidence for a better understanding of large scale transport, assessing the effect of lightning on NO<sub>x</sub> production, and studying the impact of intense mesoscale convective systems on water, aerosol, dust and chemical species in the upper troposphere and lower stratosphere. The M55 Geophysica carried out five local and four transfer flights between southern Europe and the Sahel and back, while eight stratospheric balloons and twenty-nine sondes were flown from Niamey. <br><br> These experiments allowed a characterization of the tropopause and lower stratosphere of the region. The paper provides an overview of SCOUT-AMMA campaign activities together with a description of the meteorology of the African monsoon and the situation prevailing during the flights and a brief summary of the observations accomplished.

 References Alcala, C. M. and Dessler, A. E.: Observations of deep convection in the tropics using the Tropical Rainfall Measuring Mission (TRMM) precipitation radar, J. Geophys. Res., 107, AAC-171-4, https://doi.org/10.1029/2002/D002457, 2002. %Berthelier, J. J., Simões, F., Pommereau, J. P., and Vernier, J. P.: %Observation of stratospheric charged cirrus and their relation with water %transport in the tropical UTLS, submitted, 2009. \blackbox\bf update? % %Berthelier, J. J., Simões, F., and Pommereau, J. P.: Balloon borne DC and %AC Electric Field measurements in the vicinity of tropical convective clouds, %Workshop on Coupling of Thunderstorms and Lightning Discharges to Near-Earth %Space, Corte, Corsica, June, 2008. % %Berthelier, J. J., Simões, F., and Pommereau, J. P.: Balloon observations %of impulse variations of the atmospheric electric field associated with %lightning from a tropical MCS, submitted, 2009. \blackbox\bf update? Borrmann, S., Luo, B., and Mishchenko, M.: The application of the T-matrix method to the measurement of aspherical particles with forward scattering optical particle counters, J. Aerosol Sci., 31, 789–799, 2000. Borrmann, S., Kunkel, D., Weigel, R., Minikin, A., Deshler, T., Wilson, J. C., Curtius, J., Shur, G. N., Belyaev, G. V., Law, K. S., and Cairo, F.: Aerosols in the tropical and subtropical UT/LS: in-situ measurements of submicron particle abundance and volatility, Atmos. Chem. Phys. Discuss., 9, 24587–24628, 2009. \bibitem [Brunner et al.(2009)]{brunner2009} Brunner, D., Siegmund, P., May, P. T., Chappel, L., Schiller, C., Müller, R., Peter, T., Fueglistaler, S., MacKenzie, A. R., Fix, A., Schlager, H., Allen, G., Fjaeraa, A. M., Streibel, M., and Harris, N. R. P.: The SCOUT-O3 Darwin Aircraft Campaign: rationale and meteorology, Atmos. Chem. Phys., 9, 93–117, 2009. Buontempo, C., Cairo, F., Di Donfrancesco, G., Morbidini, R., Viterbini, M., and Adriani, A. : Optical measurements of atmospheic particles from airborne platform: in-situ and remote sensing instruments for balloons and aircrafts, Ann. Geophys.-Italy, 49, 57–64, 2006. Cairo, F., Adriani, A., Viterbini, M., Di Donfrancesco, G., Mitev, V., Matthey, R., Bastiano, M., Redaelli, G., Dragani, R., Ferretti, R., Rizi, V., Paolucci, T., Bernardini, L., Cacciani, M., Pace, G., and Fiocco, G.: Polar stratospheric clouds observed during the Airborne Polar Experiment–-Geophysica Aircraft in Antarctica (APE-GAIA) campaign, J. Geophys. Res., 109, D07204, https://doi.org/10.1029/2003JD003930, 2004. Carn, S. A., Krotkov, N. A., Yang, K., Hoff, R. M., Prata, A. J., Krueger, A. J., Loughlin, S. C., and Levelt, P. F.: Extended observations of volcanic SO<sub>2</sub> and sulfate aerosol in the stratosphere, Atmos. Chem. Phys. Discuss., 7, 2857–2871, 2007. \bibitem [Chaboureau et al.(2007)]{chaboureau2007} Chaboureau, J.-P., Cammas, J.-P., Duron, J., Mascart, P. J., Sitnikov, N. M., and Voessing, H.-J.: A numerical study of tropical cross-tropopause transport by convective overshoots, Atmos. Chem. Phys., 7, 1731–1740, 2007. Corti, T., Luo, B. P., Peter, P., Vömel, H., and Fu, Q.: Mean radiative energy balance and vertical mass fluxes in the equatorial upper troposphere and lower stratosphere, Geophys. Res. Lett., 32, L06802, https://doi.org/10.1029/2004GL021889, 2005. Corti, T., Luo, B. P., de Reus, M., Brunner, D., Cairo, F., Mahoney, M. J., Martucci, G., Matthey, R., Mitev, V., dos Santos, F. H., Schiller, C., Shur, G., Sitnikov, N. M., Spelten, N., Vossing, H. J., Borrmann, S., and Peter, T.: Unprecedented evidence for overshooting convection hydrating the tropical stratosphere, Geophys. Res. Lett., 35, L10810, https://doi.org/10.1029/2008GL033641, 2008. Curtius, J., Weigel, R., Vössing, H.-J., Wernli, H., Werner, A., Volk, C.-M., Konopka, P., Krebsbach, M., Schiller, C., Roiger, A., Schlager, H., Dreiling, V., and Borrmann, S.: Observations of meteoric material and implications for aerosol nucleation in the winter Arctic lower stratosphere derived from in situ particle measurements, Atmos. Chem. Phys., 5, 3053–3069, 2005. D'Amato, F., Mazzinghi, P., and Castagnoli, F: Methane analyzer based on TDL's for measurements in the lower stratosphere: design and laboratory tests, Appl. Phys., B75, 195–202, 2002. Danielsen, E. F.: A dehydration mechanism for the stratosphere, Geophys. Res. Lett., 9(6), 605–608, 1982. Danielsen, E. F.: In situ evidence of rapid, vertical, irreversible transport of lower tropospheric air into the lower stratosphere by convective cloud turrets and by large scale up welling in tropical cyclones, J. Geophys. Res., 98, 8665–8681, 1993. de Reus, M., Borrmann, S., Bansemer, A., Heymsfield, A. J., Weigel, R., Schiller, C., Mitev, V., Frey, W., Kunkel, D., Kürten, A., Curtius, J., Sitnikov, N. M., Ulanovsky, A., and Ravegnani, F.: Evidence for ice particles in the tropical stratosphere from in-situ measurements, Atmos. Chem. Phys., 9, 6775–6792, 2009. Deshler, T., Hervig, M. E., Hofmann, D. J., Rosen, J. M., and Liley, J. B.: Thirty years of in situ stratospheric aerosol size distribution measurements from Laramie, Wyoming (41 N), using balloon-borne instruments, J. Geophys. Res., 108(D5), 4167, https://doi.org/10.1029/2002JD002514, 2003. %Deshler, T., Anderson-Sprecher, R., Jäger, H., Barnes, J., Hofmann, %D. %J., Clemesha, B., Simonich, D., Osborn, M., Grainger, R. G., and %Godin-Beekmann, S.: Trends in the nonvolcanic component of stratospheric %aerosol over the period 1971–2004, J. Geophys. Res., 111, D01201, %https://doi.org/10.1029/2005JD006089, 2006. Di Donfrancesco, G., Cairo, F., Buontempo, C., Adriani, A., Viterbini, M., Snels, M., Morbidini, R., Piccolo, F., Cardillo, F., Pommereau, J. P., and Garnier, A.: Balloonborne lidar for cloud physics studies, Appl. Optics, 45, 1–8, 2006. Durry, G., Amarouche, N., Zéninari, V., Parvitte, B., Lebarbu, T., and Ovarlez, J.: In situ sensing of the middle atmosphere with balloonborne near-infrared laser diodes, Spectrochim. Acta A, 60(4), 3371–3379, 2004. %Engelsen, O., Danielsen, T., Kift, R., Webb, and A. R.: Analysis and %reconstructions of measured vertical UV radiation profiles during %campaigns %in Thessaloniki, Greece and Niamey, Niger, submitted, 2009. %\blackbox\bf %update? Ern, M., Preusse, P., Krebsbach, M., Mlynczak, M. G., and Russell III, J. M.: Equatorial wave analysis from SABER and ECMWF temperatures, Atmos. Chem. Phys., 8, 845–869, 2008. %Fierli, F., Orlandi, E., Cairo, F., Law, K. S., et al. : Characterization of %the convective outflow in the UTLS region during the AMMA campaign: impact in %the upper troposphere and mesoscale simulations, submitted, 2009. %\blackbox\bf update? Fischer, H., Birk, M., Blom, C., Carli, B., Carlotti, M., von Clarmann, T., Delbouille, L., Dudhia, A., Ehhalt, D., Endemann, M., Flaud, J. M., Gessner, R., Kleinert, A., Koopman, R., Langen, J., López-Puertas, M., Mosner, P., Nett, H., Oelhaf, H., Perron, G., Remedios, J., Ridolfi, M., Stiller, G., and Zander, R.: MIPAS: an instrument for atmospheric and climate research, Atmos. Chem. Phys., 8, 2151–2188, 2008. %Folkins, I., Loewenstein, M., Podolske, J., Oltmans, S. J., and Profitt, %M.: %A barrier to vertical mixing at 14 km in the tropics: Evidence from %ozonesondes and aircraft measurements, J. Geophys. Res., 104, %22095–22102, %1999. % %Folkins, I., Braun, C., Thompson, A. M., and Whitte, J.: Tropical ozone %as an %indicator of deep convection, J. Geophys. Res., 107, ACH-13 1-4, %https://doi.org/10.129/2001JD001178, 2002. % %Folkins, I., Bernath, P., Boone, C., Lesins, G., Livesey, N., Thompson, %A. %M., Walker, K., and Witte, J. C.: Seasonal cycles of O<sub>3</sub>, CO and %convective %outflow at the tropical tropopause, Geophys. Res. Lett., 33, L16802, %https://doi.org/10.1029/2006GL026602, 2006. Franz, P. and Röckmann, T.: High-precision isotope measurements of H$_2^{16}$O, H$_2^{17}$O, H$_2^{18}$O, and the Δ<sup>17</sup>O-anomaly of water vapor in the southern lowermost stratosphere, Atmos. Chem. Phys., 5, 2949–2959, 2005. Fueglistaler, S., Dessler, A. E., Dunkerton, T. J., Folkins, I., Fu, Q., and Mote, P. W. : The tropical tropopause layer, Rev. Geophys., 47, RG1004, https://doi.org/10.1029/2008RG000267, 2009. Gettelman, A., Salby, M. L., and Sassi, F.: The distribution and influence of convection in the tropical tropopause region, J. Geophys. Res., 107, ACL-61-12, https://doi.org/10.1029/2001JD001048, 2002. Gettelman, A., Kinnison, D. E., Dunkerton, T. J., and Brasseur, G. P.: Impact of monsoon circulations on the upper troposphere and lower stratosphere, J. Geophys. Res., 109, D22101, https://doi.org/10.1029/2004JD004878, 2004. Gostlow, B., Robinson, A. D., Harris, N. R. P., O'Brien, L. M., Oram, D. E., Mills, G. P., Newton, H. M., and Pyle, J. A.: ?Dirac: an autonomous instrument for halocarbon measurements, Atmos. Meas. Tech. Discuss., 2, 2123–2159, 2009. Grosvenor, D. P., Choularton, T. W., Coe, H., and Held, G.: A study of the effect of overshooting deep convection on the water content of the TTL and lower stratosphere from Cloud Resolving Model simulations, Atmos. Chem. Phys., 7, 4977–5002, 2007. Hall, N. M. J. and Peyrillé, P.: Dynamics of the West African monsoon, J. Phys. IV France, 139, 81–99, 2006. Highwood, E. J. and Hoskins, B. J.: The tropical tropopause, Q. J. Roy. Meteorol. Soc., 124, 1579–1604, 1998. Hoffmann, L., Weigel, K., Spang, R., Schroeder, S., Arndt, K., Lehmann, C., Kaufmann, M., Ern, M., Preusse, P., Stroh, F., and Riese, M.: CRISTA-NF measurements of water vapor during the SCOUT-O<sub>3</sub> Tropical Aircraft Campaign, Adv. Space Res., 43, 74–81, https://doi.org/10.1016/j.asr.2008.03.018, 2009. Homan, C. D., Volk, C. M., Kuhn, A. C., Werner, A., Baehr, J., Viciani, S., Ulanovski, A., and Ravegnani, F.: Tracer measurements in the tropical tropopause layer during the AMMA/SCOUT-O3 aircraft campaign, Atmos. Chem. Phys. Discuss., 9, 25049–25084, 2009. Huntrieser, H., Schlager, H., Roiger, A., Lichtenstern, M., Schumann, U., Kurz, C., Brunner, D., Schwierz, C., Richter, A., and Stohl, A.: Lightning-produced NO<sub>x</sub> over Brazil during TROCCINOX: airborne measurements in tropical and subtropical thunderstorms and the importance of mesoscale convective systems, Atmos. Chem. Phys., 7, 2987–3013, 2007. Iannone, R. Q., Kassi, S., Jost, H.-J., Chenevier, M., Romanini, D., Meijer, H. A. J., Dhaniyala, S., Snels, M., and Kerstel E. R. T.: Development and airborne operation of a compact water isotope ratio infrared spectrometer, Isotopes in Environmental and Health Studies, 1, 99999, https://doi.org/10.1080/10256010903172715, 2009. %Immler, F., Krüger, K., Fujiwara, M., Verver, G., Rex, M., and %Schrems, %O.: Correlation between equatorial Kelvin waves and the occurrence of %extremely thin ice clouds at the tropical tropopause, Atmos. Chem. %Phys., 8, %4019–4026, 2008. Janicot, S., Thorncroft, C. D., Ali, A., Asencio, N., Berry, G., Bock, O., Bourles, B., Caniaux, G., Chauvin, F., Deme, A., Kergoat, L., Lafore, J.-P., Lavaysse, C., Lebel, T., Marticorena, B., Mounier, F., Nedelec, P., Redelsperger, J.-L., Ravegnani, F., Reeves, C. E., Roca, R., de Rosnay, P., Schlager, H., Sultan, B., Tomasini, M., Ulanovsky, A., and ACMAD forecasters team: Large-scale overview of the summer monsoon over West Africa during the AMMA field experiment in 2006, Ann. Geophys., 26, 2569–2595, 2008. Kaiser, J., Engel, A., Borchers, R., and Röckmann, T.: Probing stratospheric transport and chemistry with new balloon and aircraft observations of the meridional and vertical N<sub>2</sub>O isotope distribution, Atmos. Chem. Phys., 6, 3535–3556, 2006. Kerstel, E. R. T., Iannone, R. Q., Chenevier, M., Kassi, S., Jost, H.-J., and Romanini, D.: A water isotope (2H, 17O, and 18O) spectrometer based on optical-feedback cavity enhanced absorption for in-situ airborne applications, Appl. Phys. B, 85(2–3), 397–406, 2006. Khaykin, S., Pommereau, J.-P., Korshunov, L., Yushkov, V., Nielsen, J., Larsen, N., Christensen, T., Garnier, A., Lukyanov, A., and Williams, E.: Hydration of the lower stratosphere by ice crystal geysers over land convective systems, Atmos. Chem. Phys., 9, 2275–2287, 2009. Kylling, A., Danielsen, T., Blumthaler, M., Schreder, J., and Johnsen, B.: Twilight tropospheric and stratospheric photodissociation rates derived from balloon borne radiation measurements, Atmos. Chem. Phys., 3, 377–385, 2003. %Law, K. S.,Cairo, F., Fierli, F., Palazzi, E., Borrmann, S., Schlager, H., %Streibel, M., Viciani, S., Ravegnani, F., Volk, C. M., Schiller, C., Some, %L., et al.: Air mass origins influencing TTL chemical composition over West %Africa during 2006 summer monsoon, submitted, 2009. \blackbox\bf update? Kaiser, J., Engel, A., Borchers, R., and Röckmann, T.: Probing stratospheric transport and chemistry with new balloon and aircraft observations of the meridional and vertical N<sub>2</sub>O isotope distribution, Atmos. Chem. Phys., 6, 3535–3556, 2006. %Kley, D. and Stone, E. J.: Measurements of water vapor in the %stratosphere by %photodissotiation with Ly-alpha (1216A) light, Rev. Sci. Instrum., 49, %661–697, 1978. % %Laube, J. C., Engel, A., Bönisch, H., Möbius, T., Sturges, W. T., %Braß, M., and Röckmann, T.: Fractional release factors of %long-lived %halogenated substances in the tropical stratosphere, Atmos. Chem. Phys. %Discuss., 9, 20283-20307, 2009. Lebel, T., Parker, D. J., Flamant, C., Bourles, B., Marticorena, B., Mougin, E., Peugeot, C., Haywood, J. M., Polcher, J., Redelsperger, J.-L., and Thorncroft, C. D.: The AMMA field campaigns, Multiscale and multidisciplinary observations in the West African region, Q. J. Roy. Meteorol. Soc., 88, 311–320, 2009. Liu, C. and Zipser, E. J.: Global distribution of convection penetrating the tropical tropopause, J. Geophys. Res., 110, D23104, https://doi.org/10.1029/2005JD006063, 2005. %Liu, X., Rivière, E. D., Marécal, V. , Durry, G., Hamdouni, H., and %Arteta, J.: Water vapor budget associated to overshoots in the tropical %stratosphere: mesoscale modeling study of 4–5~August~2006 during SCOUT-AMMA, %submitted, 2009. \blackbox\bf update? Marécal, V., Durry, G., Longo, K., Freitas, S., Rivière, E. D., and Pirre, M.: Mesoscale modelling of water vapour in the tropical UTLS: two case studies from the HIBISCUS campaign, Atmos. Chem. Phys., 7, 1471–1489, 2007. %Mote, P. W., Rosenlof, K. H., McIntyre, M. E., Carr, E. S., Gille, J C., %Holton, J. R., Kinnersley, J. S., Pumphrey, H. C., Russell~III, J. M., %and %Waters, J. W.: An atmospheric tape recorder: The imprint of tropical %tropopause temperatures on stratospheric water vapor, J. Geophys. Res., %101, %3989–4006, 1996. Morel, C. and Senesi, A.: A climatology of mesoscale convective systems over Europe using satellite infrared imagery, I: Methodology, Q. J. Roy. Meteorol. Soc., 128(584), 1953–1971, 2002. Nielsen, J. K., Larsen, N., Cairo, F., Di Donfrancesco, G., Rosen, J. M., Durry, G., Held, G., and Pommereau, J. P.: Solid particles in the tropical lowest stratosphere, Atmos. Chem. Phys., 7, 685–695, 2007. Parker, D. J., Thorncroft, C. D., Burton, R. R., and Diongue-Niang, A.: Analysis of the African Easterly Jet, using aircraft observations from the JET2000 experiment, Q. J. Roy. Meteorol. Soc., 131, 1461–1482, 2005a. Parker, D. J., Burton, R. R., Diongue-Niang, A., Ellis, R. J., Felton, M., Taylor, C. M., Thorncroft, C. D., Bessemoulin, P., and Tompkins, A. M.: The diurnal cycle of the West African monsoon circulation, Q. J. Roy. Meteorol. Soc., 131, 2839–2860, 2005b. Parker, D. J., Fink, A., Janicot, S., Ngamini, J.-B., Douglas, M., Afiesimama, E., Agusti-Panareda, A., Beljaars, A., Dide, F., Diedhiou, A., Lebel, T., Polcher, J., Redelsperger, J.-L., Thorncroft, C., and Ato Wilson G.: 2008: The AMMA radiosonde program and its implications for the future of atmospheric monitoring over Africa, B. Am. Meteorol. Soc., 89, 1015–1027, 2009. Plumb, R. A.: A tropical pipe model of stratospheric transport, J. Geophys. Res., 101(D2), 3957–3972, 1996. Pommereau, J.-P., Garnier, A., Held, G., Gomes, A.-M., Goutail, F., Durry, G., Borchi, F., Hauchecorne, A., Montoux, N., Cocquerez, P., Letrenne, G., Vial, F., Hertzog, A., Legras, B., Pisso, I., Pyle, J. A., Harris, N. R. P., Jones, R. L., Robinson, A., Hansford, G., Eden, L., Gardiner, T., Swann, N., Knudsen, B., Larsen, N., Nielsen, J., Christensen, T., Cairo, F., Pirre, M., Marécal, V., Huret, N., Rivière, E., Coe, H., Grosvenor, D., Edvarsen, K., Di Donfrancesco, G., Ricaud, P., Berthelier, J.-J., Godefroy, M., Seran, E., Longo, K., and Freitas, S.: An overview of the HIBISCUS campaign, Atmos. Chem. Phys. Discuss., 7, 2389–2475, 2007. Pommereau, J.-P. and Held, G.: Is there a stratospheric fountain?, Atmos. Chem. Phys. Discuss., 7, 8933–8950, 2007. Pommereau, J.-P. and Piquard, J.: Ozone and nitrogen dioxide vertical distributions by UV-visible solar occultation from balloons, Geophys. Res. Lett., 21(13), 1227–-1230, 1994. %Popp, P. J., Marcy, T. P., Jensen, E. J., Kärcher, B., Fahey, D. W., %Gao, %R. S., Thompson, T. L., Rosenlof, K. H., Richard, E. C., Herman, R. L., %Weinstock, E. M., Smith, J. B., May, R. D., Vömel, H., Wilson, J. C., %Heymsfield, A. J., Mahoney, M. J., and Thompson, A. M.: The observation %of %nitric acid-containing particles in the tropical lower stratosphere, %Atmos. %Chem. Phys., 6, 601–611, 2006. Prata, A. J., Carn, S. A., Stohl, A., and Kerkmann, J.: Long range transport and fate of a stratospheric volcanic cloud from Soufrière Hills volcano, Montserrat, Atmos. Chem. Phys., 7, 5093–5103, 2007. Pundt, I., Pommereau, J.-P., Chipperfield, M. P., Van Roozendael, M., and Goutail, F.: Climatology of the stratospheric BrO vertical distribution by balloon-borne UV–visible spectrometry, J. Geophys. Res., 107(D24), 4806, https://doi.org/10.1029/2002JD002230, 2002. %Randel, W. J., Park, M., Wu, F., and Livesey, N. J.: A large annual %cycle in %ozone above the tropical tropopause linked to the Brewer-Dobson %circulation, %J. Atmos. Sci., 64, 4479–4488, https://doi.org/10.1175/2007JAS2409.1, 2007. Real, E., Orlandi, E., Law, K. S., Fierli, F., Josset, D., Cairo, F., Schlager, H., Borrmann, S., Kunkel, D., Volk, M., McQuaid, J. B., Stewart, D. J., Lee, J., Lewis, A., Hopkins, J. R., Ravegnani, F., Ulanovski, A., and Liousse, C.: Cross-hemispheric transport of central African biomass burning pollutants: implications for downwind ozone production, Atmos. Chem. Phys. Discuss., 9, 17385–17427, 2009. Redelsperger, J.-L., Thorncroft, C. D., Diedhiou, A., Lebel, T., Parker, D. J., and Polcher, J.: African Monsoon Multidisciplinary Analysis: An International Research Project and Field Campaign, B. Am. Meteorol. Soc., 87, 1739–1746, 2006. %Reeves, C., Ancellet, G., Bechara, J., Borgon, A., Cairo, F., Coe, H., Gomes, %L., Lambert, C., Law, K. S., Mari, C., Methven, J., Minikin, A., Nielsen, J. %K., Schlager, H., and Thouret, V.: Chemical characterization of the %troposphere over West Africa during the monsoon period as part of AMMA, %submitted, 2009. \blackbox\bf update? Ricaud, P., Barret, B., Attié, J.-L., Motte, E., Le Flochmoën, E., Teyssèdre, H., Peuch, V.-H., Livesey, N., Lambert, A., and Pommereau, J.-P.: Impact of land convection on troposphere-stratosphere exchange in the tropics, Atmos. Chem. Phys., 7, 5639–5657, 2007. Ricaud, P., Pommereau, J.-P., Attié, J.-L., Le Flochmoën, E., El Amraoui, L., Teyssèdre, H., Peuch, V.-H., Feng, W., and Chipperfield, M. P.: Equatorial transport as diagnosed from nitrous oxide variability, Atmos. Chem. Phys., 9, 8173–8188, 2009. %Richard, E. C., Tuck, A. F., Aikin, C., Kelly, K. K., Herman, R. L., %Troy, R. %F., Hovde, S. J., Rosenlof, K. H., Thompson, T. L., and Ray, A.: %High-resolution airborne profiles of CH<sub>4</sub>, O<sub>3</sub>, and water vapour near %tropical Central America in late January to early February~2004, J. %Geophys. %Res., 111, D13304, https://doi.org/10:1029/2005JD006513, 2006. Robinson, A. D., McIntyre, J., Harris, N. R. P., Pyle, J. A., Simmonds, P. G., and Danis, F.: A lightweight balloon-borne gas chromatograph for in-situ measurements of atmospheric halocarbons, Rev. Sci. Instrum., 71, 4553–4560, 2000. Rosen, J. M. and Kjome, N. T.: Backscattersonde – A new instrument for atmospheric aerosol research, Appl. Optics, 30, 1552–1561, 1991. Rossow W. B., Pearl C.: 22-Year survey of tropical convection penetrating into the lower stratosphere, Geophys. Rel. Lett., 34, L04803, https://doi.org/10.1029/2006GL028635, 2007. Schiller, C., Krämer, M., Afchine, A., Spelten, N., and Sitnikov, N.: The ice water content of Arctic, mid latitude and tropical cirrus, J. Geophys. Res., 113, D24208, https://doi.org/10.1029/2008JD010342, 2008. Schiller, C., Grooß, J.-U., Konopka, P., Plöger, F., Silva dos Santos, F. H., and Spelten, N.: Hydration and dehydration at the tropical tropopause, Atmos. Chem. Phys., 9, 9647–9660, 2009. %Sherwood, S. C. and Dessler, A. E.: Convective mixing near the tropical %tropopause: Insights from seasonal variations, J. Atmos. Sci, 60, %2674–2685, %2003. Shur, G. H., Sitnikov, N. M., and Drynkov, A. V.: A Mesoscale Structure of Meteorological Fields in the Tropopause Layer and in the Lower Stratosphere over the Southern Tropics (Brazil), Russ. Meteorol. Hydrol., 32, 487–494, 2007. Simões, F., Berthelier, J.-J., Godefroy, M., and Yahi, S.: Observation and modeling of the Earth-ionosphere cavity electromagnetic transverse resonance and variation of the D-region electron density near sunset, Geophys. Res. Lett., L14816, https://doi.org/10.1029/2009 GL039286, 2009. Sitnikov, N., Yushkov, V., Afchine, A. A., Korshunov, L. I., Astakhov, V. I., Ulanovskii, A. E., Krämer, M., Mangold, M. A., Schiller, C., Ravegnani, F. : The FLASH instrument for water vapor measurements on board the high-altitude airplane, Russian Journal on Instruments and Experimental Techniques, 50(1), 113–121, 2007. Slingo, A., Bharmal, N. A., Robinson, G. J., Settle, J. J., Allan, R. P., White, H. E., Lamb, P. J., Lele, M. I., Turner, D. D., McFarlane, S., Kassianov, E., Barnard, J., Flynn, C., and Miller, M.: Overview of observations from the RADAGAST experiment in Niamey, Niger: Meteorology and thermodynamic variables, J. Geophys. Res., 113, D00E01, https://doi.org/10.1029/2008JD009909, 2008. Schmitt, J.: Construction and testing of an in-situ NO/NO<sub>y</sub> measuring system aboard the high-altitude research aircraft M55-Geoophysica, PhD thesis, University Munich, DLR Research Report, ISRN-DLR-FB-2003-21, 2003. Smit, H. G. J., Straeter W., Johnson B. J., Oltmans S. J., Davies J., Tarasick D. W.,Hoegger B., Stubi R., Schmidlin F.J.,Northam T., Thompson A. M., Witte J. C., Boyd I., Posny F.: Assessment of the performance of ECC-ozonesondes under quasi-flight conditions in the environmental simulation chamber: Insights from the Juelich Ozone Sonde Intercomparison Experiment (JOSIE), J. Geophys. Res., 112, D19306, https://doi.org/10.1029/2006JD007308, 2007. Spang, R., Hoffmann, L., Kullmann, A., Olschewski, F., Preusse, P., Knieling, P., Schroeder, S., Stroh, F., Weigel, K., and Riese, M.: High resolution limb observations of clouds by the CRISTA-NF experiment during the SCOUT-O<sub>3</sub> tropical aircraft campaign, Adv. Space Res., 42, 1765–1775, https://doi.org/10.1016/j.asr.2007.09.036, 2008. Sultan, B. and Janicot, S.: Abrupt shift of the ITCZ over West Africa and intraseasonal variability, Geophys. Res. Lett., 27, 3353–3356, 2000. Sultan, B.,Janicot S.: The West African Monsoon Dynamics. Part II: The "Preonset" and "Onset" of the Summer Monsoon, J. Climate, 16, 3407–3427,2003. Stefanutti, L., MacKenzie, A. R., Balestri, S., Khattatov, V., Fiocco, G., Kyrö, E., and Peter, T.: Airborne Polar Experiment-Polar Ozone, Leewaves, Chemistry, and Transport (APE-POLECAT): Rationale, road map and summary of measurements, J. Geophys. Res., 104(D19), 23941–23959, 1999. Suomi, V. E. and Kuhn, P. M.: An economical net radiometer, Tellus, 10, 160–-163, 1958. %Thomas, A., Borrmann, S., Kiemle, C., Cairo, F., Volk, C. M., Beuermann, %J., %Lepuchov, B., Santacesaria, V., Matthey, R., Rudakov, V., Yushkov, V., %MacKenzie, A. R., and Stefanutti, L.: In-situ measurements of background %aerosol and subvisible cirrus in the tropical tropopause region, J. %Geophys. %Res., 107, (D24), 4763, https://doi.org/2001JD001385, 2002. Tucker, C. J., Pinzon, J. E., Brown, M. E., Slayback, D. A., Pak, E. W., Mahoney, R., Vermote, E. F., El Saleous, N.: An extended AVHRR 8-km NDVI dataset compatible with MODIS and SPOT vegetation NDVI data, Int. J. Remote Sens., 26(20), 4485–4498, 2005. Vernier, J. P., Pommereau, J. P., Garnier, A., Pelon, J., Larsen, N., Nielsen, J., Christensen, T., Cairo, F., Thomasson, L. W., Leblanc, T., and McDermid, I. S.: Tropical stratospheric aerosol layer from CALIPSO lidar observations, J. Geophys. Res., 114, D00H10, https://doi.org/10.1029/2009JD011946, 2009. Viciani, S., D'Amato, F., Mazzinghi, P., Castagnoli, F., Toci, G., and Werle, P.: A cryogenically operated laser diode spectrometer for airborne measurement of stratospheric trace gases, Appl. Phys. B, 90, 581–592, 2008. Voigt, C., Schlager, H., Luo, B. P., Dörnbrack, A., Roiger, A., Stock, P., Curtius, J., Vössing, H., Borrmann, S., Davies, S., Konopka, P., Schiller, C., Shur, G., and Peter, T.: Nitric Acid Trihydrate (NAT) formation at low NAT supersaturation in Polar Stratospheric Clouds (PSCs), Atmos. Chem. Phys., 5, 1371–1380, 2005. Voigt, C., Schlager, H., Roiger, A., Stenke, A., de Reus, M., Borrmann, S., Jensen, E., Schiller, C., Konopka, P., and Sitnikov, N.: Detection of reactive nitrogen containing particles in the tropopause region –- evidence for a tropical nitric acid trihydrate (NAT) belt, Atmos. Chem. Phys., 8, 7421–7430, 2008. Volk, C. M., Riediger, O., Strunk, M., Schmidt, U., Ravegnani, F., Ulanovsky, A., and Rudakov, V.: In situ Tracer Measurements in the Tropical Tropopause Region During APE-THESEO, Eur. Comm. Air Pollut. Res. Report, 73, 661–-664, 2000. von Hobe, M., Grooß, J.-U., Müller, R., Hrechanyy, S., Winkler, U., and Stroh, F.: A re-evaluation of the ClO/Cl<sub>2</sub>O<sub>2</sub> equilibrium constant based on stratospheric in-situ observations, Atmos. Chem. Phys., 5, 693–702, 2005. Weigel, R., Hermann, M., Curtius, J., Voigt, C., Walter, S., Böttger, T., Lepukhov, B., Belyaev, G., and Borrmann, S.: Experimental characterization of the COndensation PArticle counting System for high altitude aircraft-borne application, Atmos. Meas. Tech., 2, 243–258, 2009. Williams, E., Nathou, N., Hicks, E., Pontikis, C., Russell, B., Miller, M., and Bartholomew, M. J.: The Electrification of Dust-Lofting Gust Fronts ("Haboobs") in the Sahel, Atmos. Res., 91, 292–298, 2009. Yushkov, V., Merkulov, S., and Astakhov, V.: Optical balloon hygrometer for upper stratosphere and stratosphere water vapour measurements, in: Optical remote sensing of the atmosphere and clouds, edited by: Wang, J., Wu, B., Ogawa, T., and Guans, Z.-H., Proc. SPIE, 3501, 439–445, 1998. Yushkov, V., Oulanovsky, A., Lechenuk, N., Roudakov, I., Arshinov, K., Tikhonov, F., Stefanutti, L., Ravegnani, F., Bonafé, U., and Georgiadis, T.: A Chemiluminescent Analyzer for Stratospheric Measurements of the Ozone Concentration (FOZAN), J. Atmos. Ocean. Tech., 16, 1345–1350, 1999. Zipser, E. J., Cecil, D. J., Liu, C., Nesbitt, S. W., and Yorty, D. P.: Where are the most intense thunderstorms on Earth? B. Am. Meteorol. Soc., 1057–1071, 2006. Zöger, M., Afchine, A., Eicke, N., Gerhards, M. T., Klein, E., McKenna, D. S., Mörschel, U., Schmidt, U., Tan, V., Tuitjer, F., Woyke, T., and Schiller, C.: Fast in situ stratospheric hygrometers: A new family of balloonborne and airborne Lyman-a photofragment fluorescence hygrometers, J. Geophys. Res., 104, 1807–1816, 1999.