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dc.contributor.authorCanut, Guylaine
dc.contributor.authorCouvreux, Fleur
dc.contributor.authorLothon, Marie
dc.contributor.authorPino González, David
dc.contributor.authorSaïd, Frédérique
dc.contributor.otherUniversitat Politècnica de Catalunya. Departament de Física Aplicada
dc.identifier.citationCanut, G. [et al.]. Observations and large-eddy simulations of entrainment in the sheared sahelian boundary layer. "Boundary-layer meteorology", 16 Octubre 2011, vol. 142, núm. 1, p. 79-101.
dc.description.abstractAt the top of the planetary boundary layer, the entrainment of air, which incorporates dry and warm air from the free troposphere into the boundary layer, is a key process for exchanges with the free troposphere since it controls the growth of the boundary layer. Here, we focus on the semi-arid boundary layer where the entrainment process is analyzed using aircraft observations collected during the African Monsoon Multidisciplinary Analysis experiment and large-eddy simulations. The role of the entrainment is specifically enhanced in this region where very large gradients at the planetary boundary-layer top can be found due to the presence of the moist, cold monsoon flow on which the dry, warm Harmattan flow is superimposed. A first large-eddy simulation is designed based on aircraft observations of 5 June 2006 during the transition period between dry conditions and the activemonsoon phase. The simulation reproduces the boundary-layer development and dynamics observed on this day. From this specific case, sensitivity tests are carried out to cover a range of conditions observed during seven other flightsmade in the same transition period in order to describe the entrainment processes in detail. The combination of large-eddy simulations and observations allows us to test the parametrization of entrainment in a mixed-layer model with zero-order and first-order approximations for the entrainment zone. The latter representation of the entrainment zone gives a better fit with the conditions encountered in the Sahelian boundary layer during the transition period because large entrainment thicknesses are observed. The sensitivity study also provides an opportunity to highlight the contribution of shear stress and scalar jumps at the top of the boundary layer in the entrainment process, and to test a relevant parametrization published in the recent literature for a mixed-layer model.
dc.format.extent23 p.
dc.rightsAttribution-NonCommercial-NoDerivs 3.0 Spain
dc.subjectÀrees temàtiques de la UPC::Física
dc.subject.lcshBoundary layer (Meteorology)
dc.subject.otherLarge eddy simulation
dc.subject.otherSahelian boundary layer
dc.subject.otherSheared boundary layer
dc.titleObservations and large-eddy simulations of entrainment in the sheared sahelian boundary layer
dc.subject.lemacCapa límit (Meteorologia)
dc.contributor.groupUniversitat Politècnica de Catalunya. DF - Dinàmica No Lineal de Fluids
dc.description.peerreviewedPeer Reviewed
dc.rights.accessRestricted access - publisher's policy
local.citation.authorCanut, G.; Couvreux, F.; Lothon, M.; Pino, D.; Saïd, F.
local.citation.publicationNameBoundary-layer meteorology

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Attribution-NonCommercial-NoDerivs 3.0 Spain
Salvo que se indique lo contrario, los contenidos de esta obra estan sujetos a la licencia de Creative Commons : Reconocimiento-NoComercial-SinObraDerivada 3.0 España