Sahelian dust lifting in the inter-tropical discontinuity region: Lidar observations and mesoscale modelling - Archive ouverte HAL Access content directly
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Sahelian dust lifting in the inter-tropical discontinuity region: Lidar observations and mesoscale modelling

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Diana Bou Karam
  • Function : Author
  • PersonId : 937799
Cyrille Flamant
Pierre Tulet
Jean-Pierre Chaboureau
  • Function : Author
  • PersonId : 975044
Oliver Reitebuch
  • Function : Author
  • PersonId : 850264

Abstract

Airbone lidar observations acquired with the LEANDRE 2 system during 3 flights of the SAFIRE Falcon 20 in the framework of the AMMA Special Observing Period (SOP) 2a1 (July 2006) over western Niger, revealed the existence of desert dust uptakes in the region of the inter-tropical discontinuity (ITD) in the morning hours. Complementary observations provided by dropsondes released from the same platform as well as airborne wind measurements made from another platform (the DLR Falcon 20, flying in coordination with the SAFIRE Falcon 20) evidenced that the lifting was associated with the leading edge of the monsoon low level jet, and to be transported southward by the harmattan, above the monsoon layer. A 10-day numerical simulation, using the mesoscale model Meso-NH (including the dust emission box Dust Entrainment And Deposition model), was conducted to assess the representativity of the observed phenomenon as well as the mechanisms associated with the Sahelian dust emissions. The Meso-NH simulation (initialized by and nudged with ECMWF analyses) was carried out on a 2000 km x 2000 km domain (20-km horizontal resolution) centered at 20°N and 7°E, that included the Falcons flight track, as well as numerous AMMA-related ground-based measurement sites (Tamanrasset, Agadez, Niamey/Banizoumbou, etc..) for validation purposes. In the simulation, large dust uptakes associated with the leading edge of the monsoon flow, with a dust concentration reaching 2000μg/m3, and to be transported southward by the harmattan, above the monsoon layer, were well reproduced. On the other hand, the simulation suggested the existence of dust emissions associated with the harmattan flow which were not observed by airborne lidar measurements. The reason for the discrepancy between the model results and the lidar observations is investigated.
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Dates and versions

hal-00268040 , version 1 (22-06-2021)

Licence

Attribution - CC BY 4.0

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Cite

Diana Bou Karam, Cyrille Flamant, Pierre Tulet, Jean-Pierre Chaboureau, A. Dabas, et al.. Sahelian dust lifting in the inter-tropical discontinuity region: Lidar observations and mesoscale modelling. American Geophysical Union, Dec 2007, San Francisco, United States. ⟨hal-00268040⟩
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