ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-9-16295-2009 Aerosol vertical distribution and optical properties over M'Bour (16.96° W; 14.39° N), Senegal from 2006 to 2008 Léon J.-F. 1 4 Derimian Y. 1 Chiapello I. 1 Tanré D. 1 Podvin T. 1 Chatenet B. 2 Diallo A. 3 Deroo C. 1 Laboratoire d'Optique Atmosphérique, CNRS-Université de Lille 1, Villeneuve d'Ascq, France Laboratoire Inter-Universitaire des systèmes Atmosphériques, CNRS-Université de Paris 7–12, Créteil, France Institut de Recherche pour le Développement, Dakar, Senegal now at: Laboratoire d'Aérologie, CNRS-Université Paul Sabatier, Toulouse, France 30 07 2009 9 4 16295 16330 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/9/16295/2009/acpd-9-16295-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/9/16295/2009/acpd-9-16295-2009.pdf

We present ground-based measurements of aerosol mass, optical properties and vertical extinction profiles acquired in M'Bour, Senegal (16.96° W; 14.39° N) from January 2006 to September 2008. This place of the word is all year long affected by the export of mineral dust as it moves westward to the north Atlantic ocean. The maximum in the dust activity is observed in summer (June–July), corresponding to a maximum in the aerosol optical thickness (above 0.5) and single scattering albedo (above 0.95). It also corresponds to a maximum in the top altitude of the transported aerosol layer (up to 6 km) and aerosol optical thickness scale height (up to 3.5 km) due to the presence of the Saharan Air Layer located between 2 and 6 km. The late summer shows an additional low level aerosol layer that increases in thickness in autumn. Severe dust storms are also systematically observed in spring (March) but with a lower vertical development and a stronger impact (factor 2 to 3) on the ground-level mass compared to summer. Sporadic events of biomass burning aerosols are observed in winter (January) and particularly in January 2006 when the biomass burning aerosol are advected between 1.5 and 3.5 km high. On average, the seasonal signal in the aerosol optical properties and vertical distribution is very similar from year to year over our 3 year monitoring.

 References Ansmann, A. and Müller, D.: Lidar and atmospheric aerosol particle, in: LIDAR: Range resolved optical remote sensing of the atmosphere, edited by: Weitkamp, C., vol. 102 of Springer series in optical sciences, pp. 105–141, Springer, Geessthacht, Germany, 2005. Cattrall, C., Reagan, J., Thome, K., and Dubovik, O.: Variability of aerosol and spectral lidar and backscatter and extinction ratios of key aerosol types dervied from selected Aerosol Robotic Network locations, J. Geophys. Res., 110, D10S11, doi:10.1029/2004JD005124, 2005. Chiapello, I., Bergametti, G., Gomes, L., Chatenet, B., Dulac, F., Pimenta, J., and Santos~Suares, E.: An additional low layer transport of Sahelian and Saharan dust over the north-eastern tropical Atlantic., Geophys. Res. Lett., 22, 3191–3194, 1995. Chou, C., Formenti, P., Maillé, M., Ausset, P., Helas, G., Osborne, S., and Harrison, M.: Size distribution, shape and composition of dust aerosols collected during the AMMA SOP0 field campaign in the northeast of Niger, January 2006, J. Geophys. Res., 113, D000C10, doi:10.1029/2008JD009897, 2008. D'Almeida, G A.: A model for Saharan dust transport., J. Clim. Appl. Meteor., 25, 903–916, 1986. Derimian, Y., Léon, J.-F., Dubovik, O., Chiapello, I., Tanré, D., Sinyuk, A., Auriol, F., Podvin, T., Brogniez, G., and Holben, B.: Radiative properties of aerosol mixture observed during the dry season 2006 over M'Bour, Senegal (African Monsoon Miltidisciplinary Analysis campaign), J. Geophys. Res., 113, D00C09, doi:10.1029/2008JD009904, 2008. Dubovik, O. and King, M.: A flexible inversion algorithm for retrieval of aerosol optical properties from sun and sky radiance measurements, J. Geophys. Res., 105, 20673–20696, 2000. Dubovik, O., Holben, B., Lapyonok, T., Sinyuk, A., Mishchenko, M., Yang, P., and Slutsker, I.: Non- spherical aerosol retrieval method employing light scattering by spheroids, Geophys. Res. Lett., 29, 10, doi:10.1029/2001GL014506, 2002. Dubovik, O., Sinyuk, A., Lapyonok, T., Holben, B., Mishchenko, M., Yang, P., Eck, T., Volten, H., Munoz, O., Veihelman, B., Van~der Zand, W., Léon, J.-F., Sorokin, M., and Slutsker, I.: The application of spheroid models to account for aerosol particle non sphericity in remote sensing of desert dust, J. Geophys. Res., 111, D11208, doi:10.1029/2005JD006619, 2006. Formenti, P., Elbert, W., Maenhaut, W., Haywood, J., and Andreae, M.: Chemical composition of mineral dust aerosol during the Saharan Dust Experiment (SHADE) airborne campaign in the Cape Verde region, September 2000, J. Geophys. Res., 108, 8576, doi:10.1029/2002JD002648, 2003. Hamonou, E., Chazette, P., Balis, D., Dulac, F., Schneider, X., Galani, E., Ancellet, G., and Papayannis, A.: Characterisation of the vertical structure of Saharan dust export to the Mediterranean bassin, J. Geophys. Res., 104, 22257–22270, 1999. Hand, J. and Malm, W.: Review of aerosol mass scattering efficiencies from ground-based measurements since 1990, J. Geophys. Res., 112, D16203, doi:10.1029/2007JD008484, 2007. Haywood, J., Osborne, S., Francis, P., Keil, A., Formenti, P., Andreae, M., and Kaye, P.: The mean physical and optical properties if regional haze dominated by biomass burning aerosol measured from C-130 aircraft during SAFARI 2000, J. Geophys. Res., 108, 8473, doi:10.1029/2002JD002226, 2003. Haywood, J., Pelon, J., Formenti, P., et~al.: Overview of the dust and biomass burning experiment and African monsoon multidisciplinary analysis special observing period-0, J. Geophys. Res., 113, D00C11, doi:10.1029/2008JD010077, 2008. Heese, B. and Wiegner, M.: Vertical aerosol profiles from Raman polarization lidar observatins during the dry season AMMA field campaign, J. Geophys. Res., 113, D00C11, doi:10.1029/2007JD009487, 2008. Highwood, E., Haywood, J., Silverstone, M., Newman, S., and Taylor, J.: Radiative properties and direct effect of Saharan dust measured by the C-130 aircraft during the Saharan Dust Experiment (SHADE): 2. Terrestrial spectrum, J. Geophys. Res., 108, 8578, doi:10.1029/2002JD002552, 2003. Holben, B., Eck, T., Sluster, I., Tanré, D., Buis, J., Setzer, A., Vermote, E., Reagan, J., Kaufman, Y., Nakajima, T., Lavenu, F., Jankowiak, I., and Smirnov, Z.: AERONET-A federated instrument network and data archive for aerosol characterisation, Rem. Sens. Environ., 66, 1–16, 1998. Holben, B., Tanré, D., Smirnov, A., Eck, T., Slutsker, I., Abuhassan, N., Newcomb, W., Schafer, J., Chatenet, B., Lavenu, F., Kaufman, Y., Vande~Castle, J., Setzer, A., Markham, B., Clark, D., Frouin, R., Halthore, R., Karneli, A., O'Neill, N., Pietras, C., Pinker, R., Voss, K., and Zibordi, G.: An emerging ground-based aerosol climatology: Aerosol optical depth from AERONET, J. Geophys. Res., 106, 12067–12097, 2001. Hooper, W. and Eloranta, E.: Lidar measurements of wind in the planetary boundary layer: the method, accuracy and results from joint measurements with radiosonde and kytoon, J. Clim. Appl. Meteorol., 25, 990–1001, 1986. Jankowiak, I. and Tanré, D.: Satellite climatology of Saharan dust outbreaks: Method and preliminary results, J. Climate, 5, 646–656, 1992. Johnson, B., Osborne, S., Haywood, J., and Harisson, M.: Aircraft measurements of biomass burning aerosol over West Africa during DABEX, J. Geophys. Res., 113, D00C06, doi:10.1029/2007JD009451, 2008. Kalu, A.: The African dust plume: Its characteristics and propagation acress west Africa in winter, SCOPE, 14, 95–118, 1979. Karyampudi, V., Palm, S., Reagen, J., Fang, H., Grant, W., Hoff, R., Moulin, C., Pierce, H., Torres, O., Browell, E., and Melfi, S.: Validation of the saharan dust plume conceptual model using lidar, Meteosat, and ECMWF data, B. Am. Meteorol. Soc., 80, 1045–1075, 1999. Klett, J.: Stable analytical inversion solution for processing lidar return signal, Appl. Optics, 20, 211–220, 1981. Léon, J.-F., Pelon, J., Tanré, D., Kaufman, Y., Goloub, P., Haywood, J., and Chatenet, B.: Profiling of a Saharan dust outbreak based on a synergy between active and passive remote sensing, J. Geophys. Res., 108, 8575, doi:10.1029/2002JD002774, 2003. Li, X., Maring, H., Savoie, D., Voss, K., and Prospero, J.: Dominance of mineral dust in aerosol scattering in the North Atlantic trade winds, Nature, 380, 416–419, 1996. Mallet, M., Pont, V., Liousse, C., et~al.: Aerosol direct radiative forcing on Djougou (northern Benin) during the African Monsoon Multidisciplinary Analysis dry season experiment (SOP-0), J. Geophys. Res., 113, D00C01, doi:10.1029/2007JD009419, 2008. Moulin, C., Lambert, C., Dulac, F., and Dayan, U.: Control of atmospheric export of dust from North Africa by the North Atlantic Oscillation, Nature, 387, 691–694, 1997. Osborne, S., Johnson, B., Haywood, J., Baran, A., Harrison, M., and McConnell, C.: Physical and optical properties of mineral dust aerosol during the Dust and Biomass-burning Experiment, J. Geophys. Res., 113, D00C03, doi:10.1029/2007JD009551, 2008. Pelon, J., Mallet, M., Mariscal, A., Goloub, P., Tanré, D., Bou~Karam, D., Flamant, C., Haywood, J., Pospichal, B., and Victori, S.: Microlidar observations of biomass burning aerosol over Djougou (Benin) during African Monsoon Multidisciplinary Analysis Special Observation Period 0: Dust and Biomass Burning Experiment, J. Geophys. Res., 113, D00C18, doi:10.1029/2008JD009976, 2008. Petit, R H., Legrand, M., Jankowiak, I., Molinié, J., Asselin~de Beauville, C., Marion, G., and Mansot, J.-L.: Transport of Saharan dust over the Caribbean Islands: study of an event, J. Geophys. Res., 110, D18S09, doi:10.1029/2004JD004748, 2005. Prospero, J.: Eolian transport to the world ocean, in: The Sea, edited by: Emiliani, C., vol 7, pp. 801–874, Wiley Interscience, N.Y., 1981. Prospero, J. and Nees, R.: Impact of the North African drought and El Niño on mineral dust in the Barbados trade winds, Nature, 320, 735–738, 1986. Prospero, J M. and Carlson, T N.: Vertical and areal distribution of Saharan dust over the western equatorial north Atlantic Ocean., J. Geophys. Res., 77, 5255–5265, 1972. Rajot, J.-L., Formenti, P., Alfaro, S., et~al.: AMMA dust experiment: An overview of measurements performed during the dry season special observation period (SOP0) at the Banizoumbou (Niger) supersite, J. Geophys. Res., 113, D00C14, doi:10.1029/2008JD009906, 2008. Redelsperger, J.-L., Thorncroft, C., Diedhiou, A., Lebel, T., Parker, D., and Polcher, J.: African monsoon multidisciplinary analysis, B. Am. Meteorol. Soc., pp. 1739–1746, 2006. Schepanski, K., Tegen, I., and Macke, A.: Saharan dust transport and deposition towards the tropical northern Atlantic, Atmos. Chem. Phys., 9, 1173–1189, 2009. Seinfeld, J. and Pandis, S.: From Air Pollution to Climate Change, Atmospheric Chemistry and Physics, John Wiley, New York, 1998. Slingo, T., Ackerman, T., Allan, R., Kassianov, E., McFarlane, S., Barnard, J., Miller, H., Harries, J., Russel, J., and DeWitte, S.: Observation of the impact of a major Saharan dust storm on the atmospheric radiation balance, Geophys. Res. Lett., 33, L24817, doi:10.1029/2006GL027869, 2006. Tanré, D., Haywood, J., Pelon, J., Léon, J.-F., Chatenet, B., Formenti, P., Francis, P., Goloub, P., Highwood, E., and Myhre, G.: Measurement and modeling of the Saharan dust radiative impact: Overview of the Saharan Dust Experiment (SHADE), J. Geophys. Res., 108, 8574, doi:10.1029/2002JD003273, 2003. Tulet, P., Mallet, M., Pont, V., Pelon, J., and Boone, A.: The 7–13 March 2006 dust storm over West Africa: Generation, transport, and vertical stratification, J. Geophys. Res., 113, D00C08, doi:10.1029/2008JD009871, 2008. Turner, D., Ferrare, R., and Brasseur, L.: Average aerosol extinction and water vapor profiles over the southern great plains, Geophys. Res. Lett., 28, 4441–4444, 2001.