Vagues sur la côte aquitaine : régionalisation dynamique de 1958 à 2002

National audienceUn système de modélisation de vagues, forcé uniquement par des champs de vent a été mis en place avec le code WAVEWATCH IIITM sur une période de 44 ans (1958 à 2002) en vue d'étudier l'impact de la variabilité climatique passée sur les états de mer et sur l'érosion de la côte aquitaine. Les emboîtements hauturiers forcés par les champs de vent de la réanalyse ERA-40 ont été calibrés sur la période 1998-2002 sur 8 points de mesures. Les résultats sur 44 ans ont ensuite été validés sur 11 bouée

The Pirata Program : history, accomplishments, and future directions

Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 89 (2008): 1111–1125, doi:10.1175/2008BAMS2462.1.The Pilot Research Moored Array in the tropical Atlantic (PIRATA) was developed as a multinational observation network to improve our knowledge and understanding of ocean–atmosphere variability in the tropical Atlantic. PIRATA was motivated by fundamental scientific issues and by societal needs for improved prediction of climate variability and its impact on the economies of West Africa, northeastern Brazil, the West Indies, and the United States. In this paper the implementation of this network is described, noteworthy accomplishments are highlighted, and the future of PIRATA in the framework of a sustainable tropical Atlantic observing system is discussed. We demonstrate that PIRATA has advanced beyond a “Pilot” program and, as such, we have redefined the PIRATA acronym to be “Prediction and Research Moored Array in the Tropical Atlantic.

Improving sea level simulation in Mediterranean regional climate models

For now, the question about future sea level change in the Mediterranean remains a challenge. Previous climate modelling attempts to estimate future sea level change in the Mediterranean did not meet a consensus. The low resolution of CMIP-type models prevents an accurate representation of important small scales processes acting over the Mediterranean region. For this reason among others, the use of high resolution regional ocean modelling has been recommended in literature to address the question of ongoing and future Mediterranean sea level change in response to climate change or greenhouse gases emissions. Also, it has been shown that east Atlantic sea level variability is the dominant driver of the Mediterranean variability at interannual and interdecadal scales. However, up to now, long-term regional simulations of the Mediterranean Sea do not integrate the full sea level information from the Atlantic, which is a substantial shortcoming when analysing Mediterranean sea level response. In the present study we analyse different approaches followed by state-of-the-art regional climate models to simulate Mediterranean sea level variability. Additionally we present a new simulation which incorporates improved information of Atlantic sea level forcing at the lateral boundary. We evaluate the skills of the different simulations in the frame of long-term hindcast simulations spanning from 1980 to 2012 analysing sea level variability from seasonal to multidecadal scales. Results from the new simulation show a substantial improvement in the modelled Mediterranean sea level signal. This confirms that Mediterranean mean sea level is strongly influenced by the Atlantic conditions, and thus suggests that the quality of the information in the lateral boundary conditions (LBCs) is crucial for the good modelling of Mediterranean sea level. We also found that the regional differences inside the basin, that are induced by circulation changes, are model-dependent and thus not affected by the LBCs. Finally, we argue that a correct configuration of LBCs in the Atlantic should be used for future Mediterranean simulations, which cover hindcast period, but also for scenarios

2. Bilan énergétique et propriétés radiatives

Le système climatique* reçoit l’essentiel de son énergie du Soleil, les autres sources énergétiques, (géothermie, gravité…), étant d’un apport négligeable. Cette énergie reçue sous forme de rayonnement électromagnétique* correspond sensiblement au rayonnement d’un corps noir* d’une température de 5 800 K, donc principalement dans le domaine du visible avec une part non négligeable dans l’ultraviolet et le proche infrarouge. À sa traversée dans l’atmosphère, ce rayonnement est pour partie réfl..

Comment estimer le changement climatique ?

National audienceDétecte-t-on dans les observations un signal de changement climatique non explicable par la seule variabilité interne du climat ? Que deviendra le climat dans les décennies et siècles à venir