References

ACPD

Atmospheric Chemistry and Physics Discussions

ACPD

1680-7375

Copernicus GmbH

Göttingen, Germany

10.5194/acpd-9-20309-2009

Evidence of the impact of deep convection on reactive volatile organic compounds in the upper tropical troposphere during the AMMA experiment in West Africa

Bechara

¹ Borbon

¹ Jambert

¹ Colomb

¹ ² Perros

P. E.

Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), Universités Paris 12 et Paris 7, CNRS, 61, avenue du Général de Gaulle, Créteil, France

now at: Laboratoire d'Aérologie (LA), Université Paul Sabatier, CNRS, Toulouse, France

29 09 2009

9 5 20309 20346

This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

This article is available from http://www.atmos-chem-phys-discuss.net/9/20309/2009/acpd-9-20309-2009.html

The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/9/20309/2009/acpd-9-20309-2009.pdf

A large dataset of reactive trace gases was collected for the first time over West Africa during the African Monsoon Multidisciplinary Analysis (AMMA) field experiment in August 2006. Volatile Organic Compounds (VOC from C5–C9) were measured onboard the two French aircrafts the ATR-42 and the Falcon-20 by a new instrument AMOVOC. The goal of this study is (i) to characterize VOC distribution in the tropical region of West Africa (ii) to determine the impact of deep convection on VOC distribution and chemistry in the tropical upper troposphere (UT) and (iii) to characterize its spatial and temporal extensions. Experimental strategy consisted in sampling at altitudes between 0 and 12 km downwind of Mesoscale Convective Systems (MCS) and at cloud base. Biogenic and anthropogenic VOC distribution in West Africa is clearly affected by North to South emission gradient. Isoprene, the most abundant VOC, is at maximum level over the forest (1.26 ppb) while benzene reaches its maximum over the urban areas (0.11 ppb). First, a multiple physical and chemical tracers approach using CO, O3 and relative humidity was implemented to distinguish between convective and non-convective air masses. Then, additional tools based on VOC observations (tracer ratios, proxy of emissions and photochemical clocks) were adapted to characterize deep convection on a chemical, spatial and temporal basis. VOC vertical profiles show a "C-shaped" trend indicating that VOC-rich air masses are transported from the surface to the UT by deep convective systems. VOC mixing ratios in convective outflow are up to two times higher than background levels even for reactive and short-lived VOC (e.g. isoprene up to 0.19 ppb at 12 km-altitude) and are dependent on surface emission type. As a consequence, UT air mass reactivity increases from 0.52 s−1 in non-convective conditions to 0.95 s−1 in convective conditions. Fractions of boundary layer air contained in convective outflow are estimated to be 40±15%. Vertical transport timescale is calculated to be 25±10 min. These results characterize deep convection occurring over West Africa and provide relevant information for tropical convection parameterization in regional/global models.

References 1

Ancellet,~G., Leclair de Bellevue,~J., Mari,~C., Nedelec,~P., Kukui,~A., Borbon,~A., and Perros,~P.: Effects of regional-scale and convective transports on tropospheric ozone chemistry revealed by aircraft observations during the wet season of the AMMA campaign, Atmos. Chem. Phys., 9, 383–411, 2009.

Andrés-Hernández,~M D., Kartal,~D., Reichert,~L., Burrows,~J P., Meyer Arnek,~J., et al.: Peroxy radical observations overWest Africa during AMMA 2006: Photochemical activity in the outflow of convective systems, Atmos. Chem. Phys., 9, 3681–3695, 2009.

Atkinson,~R.: Kinetics of the gas-phase reactions of OH radicals with alkanes and cycloalkanes, Atmos. Chem. Phys., 3, 2233–2307, 2003.

Atkinson,~R., Baulch,~D L., Cox,~R A., Crowley,~J N., Hampson,~R F., et al.: Evaluated kinetic and photochemical data for atmospheric chemistry: Volume II – gas phase reactions of organic species, Atmos. Chem. Phys., 6, 3625–4055, 2006.

Bechara,~J., Borbon,~A., Jambert,~C., and Perros,~P E.: New off-line aircraft instrumentation for non-methane hydrocarbon measurements, Anal. Bioanal. Chem., 392, 865–876, 2008.

Bertram,~T H., Perring,~A E., Wooldridge,~P J., Crounse,~J D., Kwan,~A J., et al.: Direct measurements of the convective recycling of the upper troposphere, Science, 315, 816–820, 2007.

Borbon,~A., Coddeville,~P., Locoge,~N., and Galloo,~J C.: Characterising sources and sinks of rural VOC in eastern France, Chemosphere, 57, 931–942, 2004.

Carter,~W P L.: Development of ozone reactivity scales for volatile organic-compounds, J. Air Waste Manag. Assoc., 44, 881–899, 1994.

Cohan,~D S., Schultz,~M G., Jacob,~D J., Heikes,~B G., and Blake,~D R.: Convective injection and photochemical decay of peroxides in the tropical upper troposphere: Methyl iodide as a~tracer of marine convection, J. Geophys. Res.-Atmos., 104(D4), 5717–5724, 1999.

Colomb,~A., Williams,~J., Crowley,~J., Gros,~V., Hofmann,~R., et al.: Airborne measurements of trace organic species in the upper troposphere over Europe: the impact of deep convection, Environ. Chem., 3, 244–259, 2006.

Dessler,~A E.: The effect of deep, tropical convection on the tropical tropopause layer, J. Geophys. Res., 107(D3), 4033, doi:10.1029/2001JD000511, 2002.

Dickerson,~R R., Huffman,~G J., Luke,~W T., Nunnermacker,~L J., Pickering,~K E., et al.: Thunderstorms – an important mechanism in the transport of air-pollutants, Science, 235, 460–464, 1987.

Doherty,~R M., Stevenson,~D S., Collins,~W J., and Sanderson,~M G.: Influence of convective transport on tropospheric ozone and its precursors in a~chemistry-climate model, Atmos. Chem. Phys., 5, 3205–3218, 2005.

Fischer,~H., de Reus,~M., Traub,~M., Williams,~J., Lelieveld,~J., et al.: Deep convective injection of boundary layer air into the lowermost stratosphere at midlatitudes, Atmos. Chem. Phys., 3, 739–745, 2003.

Folkins,~I., Braun,~C., Thompson,~A M., and Witte,~J.: Tropical ozone as an indicator of deep convection, J. Geophys. Res.-Atmos., 107(D13), 4184, doi:10.1029/2001JD001178, 2002.

Ganzeveld,~L., Eerdekens,~G., Feig,~G., Fischer,~H., Harder,~H., et al.: Surface and boundary layer exchanges of volatile organic compounds, nitrogen oxides and ozone during the GABRIEL campaign, Atmos. Chem. Phys., 8, 6223–6243, 2008.

Granier,~C., Pétron,~G., Müller,~J.-F., and Brasseur,~G.: The impact of natural and anthropogenic hydrocarbons on the tropospheric budget of carbon monoxide, Atmos. Environ., 34, 5255–5270, 2000.

Guenther,~A., Karl,~T., Harley,~P., Wiedinmyer,~C., Palmer,~P I., and Geron,~C.: Estimates of global terrestrial isoprene emissions using MEGAN (Model of Emissions of Gases and Aerosols from Nature), Atmos. Chem. Phys., 6, 3181–3210, 2006.

Hao,~W M., Ward,~D E., Olbu,~G., and Baker,~S P.: Emissions of \chemCO_2, \chemCO, and hydrocarbons from fires in diverse African savanna ecosystems, J. Geophys. Res., 101(D19), 23577–23584, 1996.

Hauf,~T., Schulte,~P., Alheit,~R., and Schlager,~H.: Rapid vertical trace gas transport by an isolated midlatitude thunderstorm, J Geophys. Res., 100, 22957–22970, 1995.

Hauglustaine,~D A., Brasseur,~G P., Walters,~S., Rasch,~P J., Muller,~J F., Emmons,~L K., and Carroll,~C A.: MOZART, a~global chemical transport model for ozone and related chemical tracers 2. Model results and evaluation, J. Geophys. Res., 103(D21), 28291–28335, 1998.

Houze,~R A.: Mesoscale convective systems, Rev. Geophys., 42, RG4003, doi:10.1029/2004RG000150, 2004.

Karl,~T G., Christian,~T J., Yokelson,~R J., Artaxo,~P., Hao,~W M., and Guenther,~A.: The tropical forest and fire emissions experiment: method evaluation of volatile organic compound emissions measured by PTR-MS, FTIR, and GC from tropical biomass burning, Atmos. Chem. Phys., 7, 5883–5897, 2007.

Kesselmeier,~J., Kuhn,~U., Wolf,~A., Andreae,~M O., Ciccioli,~P., et al.: Atmospheric volatile organic compounds (VOC) at a~remote tropical forest site in central Amazonia, Atmos. Environ., 34, 4063–4072, 2000.

Lafore,~J P., and Moncrieff,~M W.: A~numerical investigation of the organization and interaction of the convective and stratiform regions of tropical squall lines, J. Atmos. Sci., 46, 521–544, 1989.

Lawrence,~M G., and Salzmann,~M.: On interpreting studies of tracer transport by deep cumulus convection and its effects on atmospheric chemistry, Atmos. Chem. Phys., 8, 6037–6050, 2008.

Lawrence,~M G., von Kuhlmann,~R., Salzmann,~M., and Rasch,~P J.: The balance of effects of deep convective mixing on tropospheric ozone, Geophys. Res. Lett., 30, 1940, doi:10.1029/2003GL017644, 2003.

Lelieveld,~J., and Crutzen,~P J.: Role of deep cloud convection in the ozone budget of the troposphere, Science, 264, 1759–1761, 1994.

Mari,~C H., Cailley,~G., Corre,~L., Saunois,~M., Attie,~J L., Thouret,~V., and Stohl,~A.: Tracing biomass burning plumes from the Southern Hemisphere during the AMMA 2006 wet season experiment, Atmos. Chem. Phys., 8, 3951–3961, 2008.

Martin,~R V., Jacob,~D J., Logan,~J A., Bey,~I., Yantosca,~R M., et al.: Interpretation of TOMS observations of tropical tropospheric ozone with a~global model and in situ observations, J Geophys. Res.-Atmos., 107, 4351, doi:10.1029/2001JD001480, 2002.

Nedelec,~P., Cammas,~J P., Thouret,~V., Athier,~G., Cousin,~J M., et al.: An improved infrared carbon monoxide analyser for routine measurements aboard commercial Airbus aircraft: technical validation and first scientific results of the MOZAIC III programme, Atmos. Chem. Phys., 3, 1551–1564, 2003.

Nicholson,~S E.: A~revised picture of the structure of the \qutmonsoon and land ITCZ over West Africa, Clim. Dynam., 32, 1155–1171, 2009.

Pickering,~K E., Dickerson,~R R., Huffman,~G J., Boatman,~J F., and Schanot,~A.: Trace Gas-Transport in the Vicinity of Frontal Convective Clouds, J. Geophys. Res., 93(D1), 759–773, 1988.

Poisson,~N., Kanakidou,~M., and Crutzen,~P J.: Impact of non-methane hydrocarbons on tropospheric chemistry and the oxidizing power of the global troposphere: 3-dimensional modelling results, J. Atmos. Chem., 36, 157–230, 2000.

Ray,~E A., Rosenlof,~K H., Richard,~E C., Hudson,~P K., Cziczo,~D J., et al.: Evidence of the effect of summertime midlatitude convection on the subtropical lower stratosphere from CRYSTAL-FACE tracer measurements, J. Geophys. Res.-Atmos., 109, D18304, doi:10.1029/2004JD004655, 2004.

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. Meteor. Soc., 87, 1739–1746, 2006.

Reeves,~C E., Ancellet,~G., Attie,~J.-L., Bechara,~J., Borbon,~A., et al.: Chemical characterisation of the West Africa Monsoon during AMMA, Atmos. Chem. Phys. Discuss., 9, 1585–1619, 2009.

Saxton,~J E., Lewis,~A C., Kettlewell,~J H., Ozel,~M Z., Gogus,~F., et al.: Isoprene and monoterpene measurements in a~secondary forest in northern Benin, Atmos. Chem. Phys., 7, 4095–4106, 2007.

Stevenson,~D S., Dentener,~F J., Schultz,~M G., Ellingsen,~K., van Noije,~T P C., et al.: Multimodel ensemble simulations of present-day and near-future tropospheric ozone, J. Geophys. Res.-Atmos., 111(D8), D08301, doi:10.1029/2005JD006338, 2006.

Stickler,~A., Fischer,~H., Bozem,~H., Gurk,~C., Schiller,~C., et al.: Chemistry, transport and dry deposition of trace gases in the boundary layer over the tropical Atlantic Ocean and the Guyanas during the GABRIEL field campaign, Atmos. Chem. Phys., 7, 3933–3956, 2007.

Stickler,~A., Fischer,~H., Williams,~J., de Reus,~M., Sander,~R., et al.: Influence of summertime deep convection on formaldehyde in the middle and upper troposphere over Europe, J Geophys. Res.-Atmos., 111, D14308, doi:10.1029/2005JD007001, 2006.

Ström,~J., Fischer,~H., Lelieveld,~J., and Schröder,~F.: In situ measurements of microphysical properties and trace gases in two cumulonimbus anvils over western Europe,~J. Geophys. Res., 104, 12221–12226, 1999.

Thompson,~A M., Tao,~W K., Pickering,~K E., Scala,~J R., and Simpson,~J.: Tropical deep convection and ozone formation, B. Am. Meteor. Soc., 78, 1043–1054, 1997.

Warneke,~C., Holzinger,~R., Hansel,~A., Jordan,~A., Lindinger,~W., et al.: Isoprene and its oxidation products methyl vinyl ketone, methacrolein, and isoprene related peroxides measured online over the tropical rain forest of Surinam in March 1998, J. Atmos. Chem., 38, 167–185, 2001.

Zipser,~E J., Cecil,~D J., Liu,~C T., Nesbitt,~S W., and Yorty,~D P.: Where are the most intense thunderstorms on earth?, B. Am. Meteor. Soc., 87, 1057–1071, 2006.