Evolution cyclogénétique des perturbations convectives de l'Afrique de l'Ouest et de l'Atlantique tropical

Abstract : The formation of Cape Verde Cyclones is the result of an interaction between several processes: mid-level African easterly wave's troughs and ridges, low-level monsoon flow and trade winds off the West African coast, convective developements, mid-level Saharan anticyclone, low level Saharan heat low, mid-and upper level troughs of mid-latitude origin. These processes are investigated in a climatologic study of five season of European Center for Medium-range Weather Forcast analyses and Meteosat images. This is complemented with two case studies modelled with Méso-NH: the perturbation which spawn Hurricane Helene (2006) and the so-called “Perturbation D”, a non-developing case observed during AMMA / SOP-3 in Dakar in September 2006. The simulated evolutions are quantified with energy and vorticity budgets. The main result of this thesis is that geostrophic adjustment of wind field to a pressure perturbation of convective origin in the Cape Verde Islands area occurs only if there is a production of eddy kinetic energy through barotropic conversion and a horizontal advection of cyclonic vorticity. This confirms the well-known hypothesis that tropical cyclogenesis is the result of an interaction between convective systems and a favourable environement
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Joel Arnault. Evolution cyclogénétique des perturbations convectives de l'Afrique de l'Ouest et de l'Atlantique tropical. Océan, Atmosphère. Université Paul Sabatier - Toulouse III, 2009. Français. ⟨tel-00424219⟩

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