Recherche sur les types de temps associes aux brises de mer

Les circulations de brise de mer favorisent l’apparition de types de temps relativement frais et humides mais le plus souvent ensoleillés sur les espaces côtiers par rapport aux régions intérieures. Une méthode d’identification des fronts de brise par télédétection a été appliquée à l’Europe de l’Ouest et au nord-est du Brésil, afin d’en calculer la fréquence d’apparition et la distance préférentielle de pénétration dans les terres aux heures chaudes de la journée. Le suivi des fronts de brise a été effectué durant la saison chaude en Europe occidentale (mai à septembre 2000) et la moins arrosée dans le Nord-Est du Brésil (septembre à décembre 2000). La distance de pénétration des fronts de brise varie en fonction de l’exposition de la côte aux vents dominants, en Europe comme au Brésil. Cependant, la succession de situations météorologiques variées impose des configurations diverses d’un mois à l’autre en Europe de l’Ouest, tandis de la régularité des alizés fait ressortir une plus grande permanence, dans l’espace et dans le temps, de la localisation des fronts de brise au nord-est du Brésil.The sea breeze circulations involve cool and damp but sunny weather types over coastal fringes compared to inland areas. A method of identification of the sea breeze fronts was performed and applied to Western Europe and North-eastern Brazil, in order to calculate the occurrence of sea breeze fronts during the warmest period of the day and to calculate the most frequent distance of inland penetration. The sea breeze front monitoring was carried out during the warm season in Western Europe (May-September 2000) and during the less rainy season in North-eastern Brazil (September-December 2000). In Europe and Brazil, the inland penetration of sea breeze fronts varied according to the exposure of the coast to the prevailing wind. The succession of varied meteorological situations involved varied spatial organisation of the sea breeze fronts in Western Europe, while the more regular trade winds circulation allowed a less variable space and time organisation of the sea breeze fronts in the northeast of Brazil

Utilisation de données SPOT5 pour la cartographie des habitats benthiques littoraux. Application à l’archipel des îles Chausey (golfe normand-breton, France)

Cette étude présente l’intérêt et les limites des données de télédétection à Haute Résolution Spatiale issues du capteur SPOT5 pour la cartographie des habitats benthiques médiolittoraux. Le site d’étude, l’archipel des îles Chausey (golfe normand-breton, France) se caractérise par un très vaste estran parsemé d’une multitude d’îlots. Par ses contraintes physiques, il constitue un site de recherche privilégié pour répondre aux problèmes actuels de cartographies des habitats littoraux, par ailleurs en cours de réalisation (programme REBENT-IFREMER) et initiées par les instances publiques (services délocalisés de l’État) suite aux nombreuses pollutions côtières. Des méthodes de traitement d’images traditionnelles et couramment utilisées ont été testées et validées à l’échelle de l’archipel par des photographies aériennes récentes et des campagnes d’échantillonnages faites sur le terrain. La classification retenue est très proche de celle de la nomenclature NATURA 2000 en ce qui concerne les habitats naturels de l’estran. Les traitements apportés permettent d’explorer quelques potentialités de SPOT5 et d’afficher ainsi une première évaluation de ces données pour la caractérisation, l’inventaire et le suivi des habitats naturels littoraux.Recent coastal pollutions have induced local and national authorities (research institutes – IFREMER, CNES, IFEN –, decentralised state agencies) to evaluate present mapping techniques and to assess their ability to map coastal benthic habitats. Within these research programs a test site has been choosen to evaluate data from the High Spatial Resolution Satelite SPOT5. It is the Chausey archipelago, in the English Channel which is characterized by a very wide macro tidal shore line with many skerries and very small islands. Such a rugged inter-and sub-tidal topography makes it a very demanding site for cartography. SPOT5 data has been classified (using usual routines of image processing), compared to photos, cross checked with field evidences. This has allowed to point out SPOT5 potential : the classification is very similar to the Natura 2000 check list and shows a good ability to map this type of shore. This preliminary test is a begining to a wider program of coastal monitoring by SPOT5

Submarine geomorphology and submarine landscapes of rocky platforms preceding cliffs in Brittany (France)

This paper presents a comparison between different types of submerged abrasion platforms situated on the northern and southern coasts of Brittany (France). The aim of this comparison is to understand the spatial repartition of land forms in order to produce a tool for a later mapping of these submarine forms. The main sites for this comparison are St-Malo in the North (with a 13 m tidal range) and Belle-Ile in the South (with a 8 m tidal range), though many other sites have been explored during divinf field work. The first part of this paper is an inventory of land forms at a definite scale, depending on the observation technique. The observed forms are quite variable in size and frequency. Potholes are frequent; ridges and furrows are carved by differential erosion; submarine falls create field of blocks or submarine cones of clasts; ravine are infilled with coarse material or with sand. True erosional horizontal platforms, with a smooth surface are not quite common and are only observed in the North coast, close to the surface. We infer from this observation that true wave-cut abrasion platforms can only be localised close to the surface (in this case mean tide level) and are eroded or buried if they are submerged by more than a few meters of water. This implies that geomorphological heritages play a very important role, but in some locations only. The second part tries to explain the cause of the location os submarine land forms. If all forms, beside one, are found every where, they are not located whithout an order. Their spatial combination are very peculiar and reflect conditions of exposition, of sediment availability and of structural constraint. We try to present the spatial logic of the land form repartition. To achieve this understanding we have to determine which scale is efficient to explain which dynamics. This may lead to a better understanding of sedimentary movements. The last part presents a cartography of these submarine landscape. We include algal cover as an important element for the definition of this landscape. Some maps, at different scales, are shown and commented

Segmentation et petit parcellaire: Application à des images LANDSAT TM et SPOT sur la région de l'estuaire de la Rance

International audienc

Submarine geomorphology and submarine landscapes of rocky platforms preceding cliffs in Brittany (France)

This paper presents a comparison between different types of submerged abrasion platforms situated on the northern and southern coasts of Brittany (France). The aim of this comparison is to understand the spatial repartition of land forms in order to produce a tool for a later mapping of these submarine forms. The main sites for this comparison are St-Malo in the North (with a 13 m tidal range) and Belle-Ile in the South (with a 8 m tidal range), though many other sites have been explored during divinf field work. The first part of this paper is an inventory of land forms at a definite scale, depending on the observation technique. The observed forms are quite variable in size and frequency. Potholes are frequent; ridges and furrows are carved by differential erosion; submarine falls create field of blocks or submarine cones of clasts; ravine are infilled with coarse material or with sand. True erosional horizontal platforms, with a smooth surface are not quite common and are only observed in the North coast, close to the surface. We infer from this observation that true wave-cut abrasion platforms can only be localised close to the surface (in this case mean tide level) and are eroded or buried if they are submerged by more than a few meters of water. This implies that geomorphological heritages play a very important role, but in some locations only. The second part tries to explain the cause of the location os submarine land forms. If all forms, beside one, are found every where, they are not located whithout an order. Their spatial combination are very peculiar and reflect conditions of exposition, of sediment availability and of structural constraint. We try to present the spatial logic of the land form repartition. To achieve this understanding we have to determine which scale is efficient to explain which dynamics. This may lead to a better understanding of sedimentary movements. The last part presents a cartography of these submarine landscape. We include algal cover as an important element for the definition of this landscape. Some maps, at different scales, are shown and commented

Extraction du réseau bocager à l'aide de données satellitaires Landsat Thematic Mapper. Application à un bassin versant en Bretagne Centrale

International audienc

A method of identifying and locating sea breeze fronts in north-eastern Brazil by remote sensing.

A method of identifying sea-breeze fronts by remote sensing (visible and infrared data from the GOES-8 satellite) was applied to north-eastern Brazil. The aim of the study was to estimate the frequency of observed sea-breeze fronts and the average distance they penetrate inland at 1800 UTC. During the dry season (between September and December) in 2000, the highest frequency of sea-breeze fronts was recorded on the northern fringe of the study area. The sea-breeze fronts penetrated furthest inland between September and November, with a maximum distance from the coast at Ceara of 100 km