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Low-level cloud life cycle in West Africa during the DACCIWA campaign
Jun. 26, 2018, 16:45 - 18:15
CS, IMK-TRO, Geb. 30.23, 13.OG, Seminarraum

During the monsoon season, low level clouds develop over Guinean coast and further inland at night and last until midday. These clouds have a significant radiative impact and influence the atmospheric boundary layer vertical development and therefore the daily convection. The formation of these clouds is extremely sensitive to many physical and chemical processes such as dust concentration in the atmosphere as well as dynamic and thermodynamic processes. One of the objectives of the DACCIWA project is to increase observations of low clouds in West Africa to better understand their life cycle and determine the processes that drive their formation and dissipation.

From the very good data set acquired at Savè (Benin) during the summer 2016, a conceptual model of low level cloud life cycle was developed. Gathering the results of (i) a study of an intensive day of observation, (ii) the estimation of the heat budget for several days and (iii) the statistical characteristics of the processes involved (monsoon flow, Atlantic inflow, nocturnal low-level jet and low clouds) allows to point out the important parameters for the formation of low-level clouds. The saturation is initiated by air mass cooling due to the Atlantic inflow arrival at Savè in the evening. This cooling is amplified by the low-level jet occurence which mixes up the surface air radiatively cooled with the layers above. This dynamic coupling of the layers under the clouds is also important for the dissipation of the low clouds. The experimental approach is completed by Large Eddy Simulation idealized runs involving in turn the main processes that play a role in the maintenance of low clouds: wind shear at the cloud top and at the surface, entrainment, radiative cooling, surface fluxes,...

This event is part of the eventgroup Meteorology Colloquium Karlsruhe
Dr. Fabienne Lohou

University Toulouse
Scientific Staff

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