The Quiberon 2006 experiment : description and first results on the sea-breeze local behaviour

In order to investigate the sea-breeze local behavior in complex topographical configurations, a French meteorological experimental campaign took place in the Quiberon bay (Southern Bretagne, France) during 3 weeks (June 13-29, 2006), one of the national training sites for sail racing (National Sailing School). A characteristic of this bay is the peninsula of Quiberon which is perpendicular to the general coast direction and bounds the bay on the west and partly on the south. The Quiberon bay extends over a circle 10 kilometers in diameter whose only the western half has been instrumented. The description of the experimental procedures and the first results analysis is presented here.

Meteorological masts have been installed on five sites, located inland around the bay close to the shone line. The data continuously collected include wind, turbulence, heat and momentum fluxes, temperature and humidity at various altitudes between ground and 30m above mean sea level. The incoming radiation and the daytime wind profiles, measured with a SODAR up to a few hundred meters, supplement these data. Every day, four instrumented light catamarans) were positioned off-shore at selected points according to the weather conditions in order to document the wind 5m above the sea.

This database is analyzed here for the 3 days when large-scale sea-breeze events occurred, with a special focus on the site-specific influences such as the topographical cuts of the coastline, the wind skirting around the peninsula and the enhancement of the breeze in some directions due to the coastline orientation. .

In the very near future, this database will be used to validate and in combination with high resolution simulations performed with the atmospheric model ARPS. Other simulations will then be performed in more extreme conditions not encountered during the campaign in order to better assess the very complex sea-breeze processes of this bay.