Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 10 2 2010 10.5194/acpd-10-3053-2010 http://www.atmos-chem-phys-discuss.net/10/3053/2010/ http://www.atmos-chem-phys-discuss.net/10/3053/2010/acpd-10-3053-2010.html http://www.atmos-chem-phys-discuss.net/10/3053/2010/acpd-10-3053-2010.pdf 3053 3086 2010-02-05 Impacts of dust on West African climate during 2005 and 2006 M. Camara moctar1sn@yahoo.fr G. Jenkins A. Konare Département de Physique, Université de Ziguinchor, BP 523, Ziguinchor, Senegal Physics and astronomy department, Howard University, DC, 20059, USA Université de Cocody, Abidjan 22, BP 582, Côte d'Ivoire Laboratoire de Physique de l'atmosphère &ndash; SF, BP 5085 Dakar-Fann, Senegal The aim of this study is to understand the impacts of Saharan dust outbreaks on West African climate using a 3-dimensional, hydrostatic, sigma vertical coordinate regional climate model (RegCM). We performed a simulation with the non aerosol version of the model (control case) followed by another simulation using the desert dust module (dust case) implemented in RegCM which includes emission, transport, gravitational settling, wet and dry removal and calculation of dust optical properties for 2005 and 2006. Dynamic and thermodynamic parameters obtained from both versions of the model are intercompared and validated with NCEP/NCAR reanalysis, African Monsoon Multidisciplinary Analysis (AMMA) program data and the Global Precipitation Climatology Project (GPCP) rainfall products. The spatial and temporal distribution of the Aerosol optical depth derived from the desert dust run is compared to available observed aerosol data such as the Aerosol Robotic Network (AERONET) program and satellites data. <br><br> Using radiosounding data and RegCM outputs, a case study of a strong dust outbreak showed the presence of a stable environment at Dakar, Sal and Nouadhibou stations. Berry,~G J. and Thorncroft,~C D.: Case study of an intense African easterly wave, Mon. Weather Rev., 133, 752–766, 2005. Burpee,~R W.: The origin and structure of easterly waves in the lower troposphere of North Africa, J Atmos Sci., 29, 77–90, 1972. Carlson,~T N.: Some remarks on African disturbances and their progress, Mon. Weather Rev., 97, 716–728, 1969. Dickinson,~R., Henderson-Sellers,~A., and Kennedy,~P.: Biosphere-atmosphere transfer scheme (BATS) version 1e as coupled to the NCAR community climate model. Technical Report NCAR/TN-387+STR, NCAR Boulder, Colorado, 1993. Dunion,~J P. and Velden,~C S.: The impact of the Saharan air layer on Atlantic tropical cyclone activity, B Am. Meteorol. Soc., 85(3), 353–365, 2004. Engelstaedter,~S. and Washington,~R.: Atmospheric control on the annual cycle of North African dust, J Geophys. Res., 112, D03103, \doi10.1029/2006JD007195, 2007. Giorgi,~F., Marinucci,~M., and Bates,~G.: Development of a~second generation regional climate model (RegCM). Part~I: Boundary layer and radiative transfer processes, Mon. Weather Rev., 121, 2794–2813, 1993a. Giorgi,~F., Marinucci,~M., and Bates,~G.: Development of a~second generation regional climate model (RegCM). Part~II: Convective processes and assimilation of lateral boundary conditions, Mon. Weather Rev., 121, 2814–2832, 1993b. Gong,~S L., Zhang,~X Y., Zhao,~T L., McKendry,~I G., Jaffe,~D A., and Lu,~N M.: Characterization of soil dust aerosol in China and its transport and distribution during 2001 ACE-Asia: model simulation and validation, J Geophys. Res., 108(D9), 4262, doi:10.1029/2002JD002633, 2003. Goudie,~A S. and Middleton,~N J.: Saharan dust storms: nature and consequences, Earth Sci.-Rev., 56(1–4), 179–204, 2001. Grell,~G A.: Prognostic evaluation of assumptions used by cumulus parameterizations, Mon. Weather Rev., 121, 764–787, 1993. Janicot,~S.: Variabilité des précipitations en Afrique de l'Ouest et circulations quasi-stationnaires durant une phase de transition climatique, Thèse de doctorat, Paris VI, 600~pp., 1990. Jenkins,~G., Gaye,~A., and Sylla,~B.: Late 20th century attribution of drying trends in the Sahel from the Regional Climate Model (RegCM3), Geophys. Res. Lett., 32, L22705, doi:10.1029/2005GL024225, 2005. Kalnay,~E., Kanamitsu,~M., Kistler,~R., Collins,~W. et~al.: The NCEP/NCAR 40 year reanalysis project, B Am. Meteorol. Soc., 77, 437–471, 1996. Kiehl,~J., Hack,~J., Bonan,~G. et~al.: Description of the NCAR community climate model (ccm3), Technical report, National Center for Atmosheric Research, 1996. Konare,~A., Zakey,~A S., Solmon,~F., Giorgi,~F., Rauscher,~S., Ibrah,~S., and Bi,~X.: A~regional climate modelling study of the effects of desert dust on the West African monsoon, J Geophys. Res., 113, D12206, \doi10.1029/2007JD009322, 2008. Miller,~R L., Tegen,~I., and Perlwitz,~J.: Surface radiative forcing by soil dust aerosols and the hydrologic cycle, J Geophys. Res., 109, D04203, \doi10.1029/2003JD004085, 2004. Miller,~R L. and Tegen,~I.: Climate response to soil dust aerosols, J. Climate, 11, 3247–3267, 1998. Ozer,~P.: Les lithometeores en region sahelienne, Int J. Trop. Ecol. Geogr., 24, 1–317, 2001. Penner, J. E., Andreae, M., Annegarn, H., Barrie, L., Feichter, J., Hegg, D., Jayaraman, A., Leaitch, R., Murphy, D., Nganga,J., Pitari, G., et al.: Aerosol, their direct and indirect effects, in: Climate Change 2001: the Scientific Basis, Contribution of Working Group~I to the Third Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Hougton,~J T., Ding,~Y., Griggs,~D J. et~al., Cambridge University Press, New York, chap. 5, 291–336, 2001. Reed,~R J., Norquist,~D., and Recker,~E E.: The structure and properties of African wave disturbances as observed during Phase~III of GATE, Mon. Weather Rev., 105, 317–333, 1977. Solmon,~F., Mallet,~M., Elguindi,~N., Giorgi,~F., Zakey,~A., and Konare,~A.: Dust aerosol impact on regional precipitation over Western Africa, mechanisms and sensitivity to absorption properties, Geophys. Res. Lett., 35, L24705, \doi10.1029/2008GL035900, 2008. Song,~C H. and Carmichael,~G R.: A~three dimensional modelling investigation of the evolution processes of dust and sea-salt particles in East Asia, J Geophys. Res., 103, 18131–18154, 2001. Sultan,~B. and Janicot,~S.: The West African monsoon dynamics: Part~II: The \squtpreonset and \squtonset of the summer monsoon, J Climate, 16, 3407–1586, 2003. Walsh,~J J. and Steidinger,~K A.: Saharan dust and Florida red tides: the cyanophyte connection, J Geophys. Res., 106(C6), 11597–11612, 2001. Yoshioka M., Mahowald, N., Conley, A., Collins, W., Fillmore, D., Zender, C., and Coleman, D.: Impact of desert dust radiative forcing on Sahel precipitation: relative importance of dust compared to sea surface temperature variations, vegetation changes and greenhouse gaz warming, J Climate, 20, 1445–1467, 2007. Zakey,~A S., Solmon,~F., and Giorgi,~F.: Implementation and testing of a~desert dust module in a~regional climate model, Atmos. Chem. Phys., 6, 4687–4704, 2006.