THE BODÉLÉ DEPRESSION (CHAD): WHEN THE VENTURI EFFECT PROPELLES DUST FROM THE SAHARA TOWARDS THE AMAZON BASIN

B. REMINI

Abstract


This paper answers the question: How can a region as small as the Bodélé Depression continuously supply large amounts of dust to the Amazon Basin? To answer this question, you must know that millions of tons of dust to fly over more than 4000 km must first be lifted into the upper atmosphere. Such a criterion can only be satisfied by the existence of very violent winds that last several days. This condition was dictated by the geography and geomorphology of the Bodélé region. The adequate layout of the Tibesti and Ennedi mega-obstacles upstream of the Bodélé offers the most beautiful Venturi on the planet. In a very rare case, 3 pass areas participate at the same time to increase the wind speed. These are the passes of Tibesti (south-east), Ennedi (north-west) and Bembéché (under the Venturi effect). The harmattan wind from Libya and Egypt rushes into the Borkou tunnel and escapes from Bembéché (the pass) with much greater speed. The detachment of the air streams from the obstacles takes place in the detachment area (Largeau), which is accompanied by gigantic vortices, thus lifting the dust into the atmosphere. Thus, during the last 20 years, approximately 503 dust uplifts have been recorded at the level of the Bodélé depression, i.e., 58% of the total number of uplifts recorded in the Sahara. The great storms we have called effective upheavals. These are long-lasting dust lifts that exceed 7 days. These storms can send fine particles toward the Amazon. Each year, 2 to 3 effective uprisings per year are recorded in the Bodélé depression.

Keywords


Amazonia, Sahara, Dust rising, Dust plume, Bodélé, Tibesti-Ennedi

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References


ALINE T. (2016). African Sahara nurtures Amazonian vegetation, NASA information. Actua Latino. http://www.actulatino.com, publié le 30 mars 2016.

ALTENDORF D. (2021). A look back at 'Godzilla', the record-breaking dust cloud that crossed the Atlantic in June 2020. SciencePost (Planet and Environment). Posted May 31, 2021. https://sciencepost.fr/retour-sur-godzilla-le-nuage-de-poussiere-record-qui-a-traverse-latlantique-en-juin-2020/

BARTHÉLÉMY P., 2015. The Amazon fertilized by the sand of the Sahara. Passeur de sciences. http://passeurdesciences.blog.lemonde.fr. Publish March 1, 2015.

BING P., QINJIAN J. (2021). A Record-Breaking Trans-Atlantic African Dust Plume Associated with Atmospheric Circulation Extremes in June 2020. Bulletin of the American Meteorological Society. DOI: https://doi.org/10.1175/BAMS-D-21-0014.1 Vol. 102, N°7, pp. 1340-1356.

BORUNDA A. (2020). Sahara dust: precious for the climate harmful to our Health. National Geographic. https://www.nationalgeographic.fr/sciences/2020/07/ poussiere-du-sahara-precieuse-pour-le-climat-novice-pour-notre-sante

BRISTOW C.S., DRAKE N., ARMITAGE S.(2009). Deflation in the dustiest place on Earth: The Bodélé Depression, Chad. Geomorphology. https://doi.org/10.1016/ j.geomorph.2007.12.014. Vol. 105, No 1–2, April, pp. 50-58.

CHAVETNOIR A. (2015). How the Sahara continually fertilizes the Amazon. Futura-Sciences, uploaded March 5, http://www.maxisciences.com/sahara

CHEPIL W.A. (1951). Properties of soil which influence wind erosion. Soil science, No 72, pp. 387-401.

COOK K.H. (1999). Generation of the African Easterly Jet and Its Role in Determining West African Precipitation », Journal of Climate, Vol. 12, No 5, pp. 1165-1184.

DURAND DE CORBIAC H. (1958). "Gone with the wind" or erosion and wind accumulation around Tibesti. Newsletter of the Association of Geographical Engineers, No11, July, pp. 147-155.

GREY E. (2015). NASA: the sand of the Sahara fertilizes the Amazonian forest. Écologie. Ma. https://ecolgie.ma, published on February 28, 2015.

GILES J. (2005). Chad. Stuck in the dustiest place on earth. International mail. Posted August 3.https://www.courrierinternational.com/article/2005/08/04/coinces-dans-l-endroit-le-plus-poussiereux-de-la-planete

HAUG A. (2015). How Saharan sand fertilizes the Amazon rainforest. Futura Planète. Published February 27, 2015. https://www.futura-sciences.com/planete/actualites/ environnement-sable-sahara-fertilise-foret-amazonienne-57312/

KOREN I., KAUFMAN Y.J., WASHINGTON R., TODD M.C., RUDICH Y., MARTINS J.V., ROSENFELD D. (2009). The Bodélé depression: a single spot in the Sahara that provides most of the mineral dust to the Amazon forest. Environmental Research Letters, Vol.1, No1. doi:10.1088/1748-9326/1/1/014005

MAINGUET M. ET CHEMIN M. Ch. (1990). The Tibesti massif in the Sahara wind system. Reflection on the genesis of Lake Chad. Berliner Geographische Studien, N° 30, pp. 261-276.

MAINGUET M., CHEMIN M.CH. ET BORDE J.M. (1983). Study of the role of topographical obstacles in wind circulation based on satellite images and aerial photographs from the continental scale to that of the control mound. Méditerranée Télédétection, No 3, pp. 11-19.

REMINI B., MAINGUET M. ET DUMAY F. (2011). Impact of the parameters of a morphological and morphometric of meg-obstacle on the field schelter. Geographia Technica, No 1, pp. 57 - 71

REMINI B. (2001). Mega obstacles; their influence on wind dynamics and the silting up of oasis areas. Doctoral thesis in Geography. University of Reims Champagne-Ardenne, Reims, France.

REMINI B. (2022). When the sand of the Sahara leaves its territory – mechanism of dust rising. Larhyss Journal, No 49, Mars, pp. 139-164

REMINI B. (2020). Awesome, the dust of the Sahara in the sky of the America continent Godzilla, the biggest dust storm in half a century, Larhyss Journal, No 43, pp. 139- 167.

REMINI B., MAINGUET M., DUMAY F. (2011). Impact of the parameters of a morphological and morphometric of mega-obstacle on the field schelter, Geographia Technica, No 1, pp. 57 – 71.

REMINI B. (2001). Mega-obstacles; their influence on wind dynamics and the silting up of oasis areas, PhD thesis in Geography, University of Reims Champagne - Ardenne, Reims, France.

REMINI B. (2017). When two opposing ecosystems: wet and dry are linked by the phenomenon of erosion? Case of the Sahara desert and the Amazon rainforest. Larhyss Journal, No 31, pp. 259-295.

REMINI B. (2018). Tibesti-Ennedi-Chad Lake: the triangle of dust impact on the fertilization of the Amazonian forest, Larhyss Journal, No 34, pp. 147-182.

RFI (2014). Le Tchad, première «source» de poussière au monde. RFI Afrique. Publié le 16 mars. https://www.rfi.fr/fr/afrique/20140316-le-tchad-premiere-source-poussiere-monde-bodele.

SOUTO E. (2014). Sand and dust: the Sahara feeds the Amazon. ConsoGlobe. www.consoglobe. Published November 24, 2014.

VERSTAPPEN H. Th., VAN ZUIDAM R.A. (1970). Orbital photography and the geosciences. A Geomorphological Example from the central Sahara, Geoforum, No 2, pp.33-47.

WASHINGTON R., TODD M.C. (2005). Atmospheric controls on mineral dust emission from the Bodélé depression Chad: the role of the low level jet, Geophysical Research letters, Vol. 32, L17701. doi:101029/2005 GL 023597

WASHINGTON R., TODD M.C., ENGRLSTAEDTER S., MABAINAGEL S., MITCHELL F. (2006a). Dust and the low-level circulation over the Bodélé depression, Chad: pbservations from BoDEx, Journal of Geophysical Research, Vol. 111, DO3201. doi: 101029/2005JD006502.

WASHINGTON R., TODD M.C., LIZCANO G., TEGEN I., FLAMANT C., KOREN I., GINOUX P., ENGELSTAEDTER S., BRISTOW C.S., ZENDER C.S., GOUDIE A.S., WARREN A., PROSPERO J.M. (2006b). Links between topography, wind, deflation, lakes and dust: The case of the Bodélé ́ Depression, Chad. Geophysical Research Letters, Vol. 33, L09401. doi:10.1029/2006GL025827

YU H., CHIN M., YUAN T., BIAN H., REMER L.A., PROSPERO J.M., OMAR A., WINKER D., YANG Y., ZHANG Y., ZHANG Z., ZHAO Z.C. (2015). The fertilizing role of African dust in the Amazon rainforest: first multiyear assessment based on data from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations, Geophysical. Research Letters, No42, pp. 1984–1991. Doi:10.1002/2015GL063040.


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