This work is a part of a research program aiming to develop tools allowing to optimize the tactical decision process during onshore sailing races in complex micrometeorological situations. Our goal is to enhance the knowledge of the windshifts in coastal racecourses. A study of the Quiberon bay micrometeorology has been set up, including measurements and numerical simulations. Several meteorological situations have been encountered during the "Quiberon2006" measurement campaign that was carried out from June 16-29, 2006. The analysis of the measurement data, based on a synoptic wind quadrant classification, shows how the breeze behavior is influenced by the gradient wind. High resolution large eddy simulations (1 km to 100 m horizontal meshes) have been performed with the "ARPS" atmospheric numerical model to put in light the influence of a complex coastline (including a peninsula) on the local winds. The local topography and land use have been finely modelled using the Corine Land Cover european database. Lateral boundary conditions for the regional scale simulations were generated using the WRF model. The measurement results are compared to numerical results in view of validating the ability of the numerical models to simulate coastal micrometeorological phenomena in a complex topographical situation. High-resolution numerical simulations provide a quantification of some local small-scale coastal effects at small-scale that would hardly be seen in measurements.
