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Dust emissions over the Sahel associated with the West African monsoon intertropical discontinuity region: A representative case-study

Bou Karam, D. and Flamant, C. and Knippertz, P. and Reitebuch, O. and Pelon, J. and Chong, M. and Dabas, A. (2008) Dust emissions over the Sahel associated with the West African monsoon intertropical discontinuity region: A representative case-study. Quarterly Journal of the Royal Meteorological Society, 134, pp. 621-634. DOI: 10.1002/QJ.244.

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Official URL: http://www3.interscience.wiley.com/journal/113388514/home

Abstract

Near-dawn airborne lidar and dropsonde observations acquired on 7 July 2006, during the African Monsoon Multidisciplinary Analysis (AMMA) Special Observing Period 2a1, were used to investigate dust mobilization, lifting and transport in the intertropical discontinuity (ITD) region over western Niger. Atmospheric reflectivity data from the LEANDRE 2 lidar system enabled us to analyse the structure of dust plumes in the context of wind and thermodynamic information provided by the WIND lidar system and dropsondes. Dust mobilization was mainly observed in two locations: (a) within the monsoon flow as the result of the passage of a density current originating from a mesoscale convective system over southwest Niger, and (b) at the leading edge of the monsoon flow where the near-surface winds and turbulence were strong, because the monsoon flow was behaving as an intrusive density current. The circulation in the head of the monsoon density current lifted the mobilized dust towards the wake, along an isentropic surface. Behind and away from the leading edge, some of the mobilized dust was observed to mix across the monsoon-harmattan interface, due to the existence of mechanical shear above the monsoon layer. The dust thus becomes available for long-range transport by the harmattan. Because dust sources are widespread over the Sahel and presumably active on many days when the ITD is located in this region during summer, dust emissions associated with the described mechanism may influence the radiation budget over West Africa.

Document Type:Article
Title:Dust emissions over the Sahel associated with the West African monsoon intertropical discontinuity region: A representative case-study
Authors:
AuthorsInstitution or Email of Authors
Bou Karam, D.Univ. Pierre et Marie Curie, Paris, F
Flamant, C.Univ. Pierre et Marie Curie, Paris, F
Knippertz, P.Johannes Gutenberg-Univ. Mainz
Reitebuch, O.UNSPECIFIED
Pelon, J.Univ. Pierre et Marie Curie, Paris, F
Chong, M.Univ. de Toulouse, Toulouse, F
Dabas, A.Meteo-France, Toulouse, F
Date:2008
Journal or Publication Title:Quarterly Journal of the Royal Meteorological Society
Volume:134
DOI:10.1002/QJ.244
Page Range:pp. 621-634
Status:Published
Keywords:AMMA, Wind Lidar, Dust
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EO - Erdbeobachtung
DLR - Research area:Space
DLR - Program:W EO - Erdbeobachtung
DLR - Research theme (Project):W - Projekt ADM II (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Lidar
Deposited By: Oliver Reitebuch
Deposited On:08 Dec 2008
Last Modified:12 Dec 2013 20:34

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