On the corrections of ERA-40 surface flux products consistent with the Mediterranean heat and water budgets and the connection between basin surface total heat flux and NAO

This is a study of heat fluxes and heat budget of the Mediterranean Sea using the European Centre for Medium-Range Weather Forecasts (ECMWF) 45 year reanalysis data set ERA-40. The simple use of the ERA-40 surface flux components fails to close the budget and, in particular, the shortwave radiation flux is found to be underestimated with respect to observed data by about 10%. The heat flux terms are recomputed and corrected in order to close the heat and freshwater budgets of the Mediterranean basin over the period 1958 to 2001, thus producing a corrected ERA-40 surface flux data set. Various satellite and in situ observational data are used to construct spatially varying corrections to the ERA-40 products needed to compute the air-sea fluxes. The corrected interannual and climatological net surface heat and freshwater fluxes are and , respectively, which are regarded as satisfactorily closing the Mediterranean heat and water budgets. It is also argued that there is an important contribution from large heat losses associated with a few severe winters over the Mediterranean Sea. This is shown to be related to wind regime anomalies, which strongly affect the latent heat of evaporation that is the main responsible for the interannual modulation of the total heat flux. Furthermore, the surface total heat flux anomaly time series is compared with the North Atlantic Oscillation (NAO) index, and the result is a positive correlation with ocean warming for positive NAO index and cooling associated to negative index periods

On the corrections of ERA-40 surface flux products consistent with the Mediterranean heat and water budgets and the connection between basin surface total heat flux and NAO

This is a study of heat fluxes and heat budget of the Mediterranean Sea using the European Centre for Medium␣Range Weather Forecasts (ECMWF) 45 year reanalysis data set ERA␣40. The simple use of the ERA␣40 surface flux components fails to close the budget and, in particular, the shortwave radiation flux is found to be underestimated with respect to observed data by about 10%. The heat flux terms are recomputed and corrected in order to close the heat and freshwater budgets of the Mediterranean basin over the period 1958 to 2001, thus producing a corrected ERA␣40 surface flux data set. Various satellite and in situ observational data are used to construct spatially varying corrections to the ERA␣40 products needed to compute the air␣sea fluxes. The corrected interannual and climatological net surface heat and freshwater fluxes are ␣7 W/m2 and ␣0.64 m/yr, respectively, which are regarded as satisfactorily closing the Mediterranean heat and water budgets. It is also argued that there is an important contribution from large heat losses associated with a few severe winters over the Mediterranean Sea. This is shown to be related to wind regime anomalies, which strongly affect the latent heat of evaporation that is mainly responsible for the interannual modulation of the total heat flux. Furthermore, the surface total heat flux anomaly time series is compared with the North Atlantic Oscillation (NAO) index, and the result is a positive correlation with ocean warming for positive NAO index periods and ocean cooling associated with negative index periods.The OI␣SST products used in this paper were jointly produced by ENEA Department of Environment, Global Change and Sustainable Development and Gruppo Oceanografia da Satellite (GOS) of the CNR␣ISAC (Istituto di Scienze dell’Atmosfera e del Clima) as part of the EU project MFSTEP (EVK3␣CT␣2002␣00075). The National Center for Atmospheric Research is sponsored by the National Science Foun- dation. The in situ AGIP data were kindly supplied by ENI␣AGIP division, Milan. This work was supported by the European Commission MyOcean Project (SPA.2007.1.1.01, development of upgrade capabilities for existing GMES fast␣track services and related operational services, grant agreement 218812␣1␣FP7␣SPACE 2007).PublishedC060224.6. Oceanografia operativa per la valutazione dei rischi in aree marineJCR Journalreserve

Turbulence and stratification in Priest Pot, a productive pond in a sheltered environment.

Priest Pot is an example of the abundant ponds which, collectively, contribute crucially to species diversity. Despite extensive biological study, little has been reported about the physical framework which supports its ecological richness. This paper elucidates the physical character of Priest Pot�s water column and thus that of similar waterbodies. Vertical thermal microstructure profiles were recorded during summer 2003, and analysed alongside concurrent meteorological data. During summer stratification, the thermal structure appeared to be dominated by surface heat fluxes. Surface wind stress, limited by sheltering vegetation, caused turbulent overturns once a surface mixed layer was present, but appeared to contribute little to setting up the thermal structure. Variations in full-depth mean stratification occurred pre-dominantly over seasonal and ~5-day time scales, the passage of atmospheric pressure systems being posited as the cause of the latter. In the uppermost ~0.5 m, where the stratification varied at sub-daily time scales, turbulence was active (sensu Ivey and Imberger, 1991) when this layer was mixed, with dissipation values � ~ 10-8 m2s-3 and vertical diffusivity KZ = 10-4-10-6 m2s-1. Where the water column was stratified, turbulence was strongly damped by both buoyancy and viscosity and KZ was an order of magnitude smaller. Vertical transport in the mixed layer occurred via many small overturns (Thorpe scale rms and maximum values typically 0.02m and 0.10m respectively) and seston were fully mixed through the water column

Decomposing rhythm processing: Electroencephalography of perceived and self-imposed rhythmic patterns

Contains fulltext : 99240.pdf (publisher's version ) (Open Access)Perceiving musical rhythms can be considered a process of attentional chunking over time, driven by accent patterns. A rhythmic structure can also be generated internally, by placing a subjective accent pattern on an isochronous stimulus train. Here, we investigate the event-related potential (ERP) signature of actual and subjective accents, thus disentangling low-level perceptual processes from the cognitive aspects of rhythm processing. The results show differences between accented and unaccented events, but also show that different types of unaccented events can be distinguished, revealing additional structure within the rhythmic pattern. This structure is further investigated by decomposing the ERP into subcomponents, using principal component analysis. In this way, the processes that are common for perceiving a pattern and self-generating it are isolated, and can be visualized for the tasks separately. The results suggest that top-down processes have a substantial role in the cerebral mechanisms of rhythm processing, independent of an externally presented stimulus.12 p