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Highlights • Evaluation of the role of aerosols in the spatiotemporal variability of photovoltaic productivity in a large area. • Evaluation of regional climate model simulations for photovoltaic energy modeling. • Different tracking systems for the photovoltaic generators are considered. • The results show a non-negligible effect of aerosols in photovoltaic production. Abstract The increase in the photovoltaic energy installed capacity over the world leads to the need of a better understanding of solar resource and its variability. The aim of this work is to assess the influence of aerosols on photovoltaic energy production from seasonal to multi-decadal time scales. For this purpose we use various coupled aerosol-climate simulations that take into account the complex spatial and temporal patterns of natural and anthropogenic aerosols over the Euro-Mediterranean domain. The results show that aerosols strongly influence the spatial pattern, seasonal cycle and long-term trend of PV production. The most affected area is Central Europe where sensitivity of PV production to aerosols is higher. The annual production loss due to aerosols ranges from no impact to - 16 % in The Netherlands, with variation depending on the area and on the typology of the tracking system. The summer production loss can even reach - 20 % over regions of Africa and Syria-Iraq. We conclude that aerosols cannot be neglected in the assessment of PV production at large time scales over the Euro-Mediterranean area. Besides, the potential increase in energy due to reduction in the anthropogenic aerosols is shown in the simulation of the brightening period over Europe, with an increase of 2000 kW h kWp in a PV lifetime for the most affected areas. It illustrates the evolution that PV potential could follow in highly polluted areas through the effective implementation of pollution control measures. [ABSTRACT FROM AUTHOR]

Abstract: Sea level trends and inter-annual variability in the Mediterranean Sea for the period 1960–2000 is explored by comparing observations from tide gauges with sea level hindcasts from a barotropic 2D circulation model, and two full primitive equation 3D ocean circulation models, a regional one and the Mediterranean component of a global one,. In the 2D model, 50% of the sea level variance was found to result from the wind and atmospheric pressure forcing. In the 3D models, 20% of the sea level variance was explained by the steric effects. The sea level residuals at the tide gauges locations, calculated by subtraction of the 2D model output from the sea level observations are significantly correlated (r =0.4) with the steric signals from the 3D models. After the removal of the atmospheric and the steric contributions the tide-gauge sea level records indicate a period where sea level was stable (1960–1975) and a period where sea level was rising (1975–2000) with rates in the range 1.1–1.8 mm/yr. A part of the residual trend can be explained by the contribution of local land movements (0.3 mm/yr) while its major part indicates a global signal, probably mass addition, appearing after 1975. [Copyright &y& Elsevier]

Abstract: An Atmosphere-Ocean Regional Climate Model coupled over the Mediterranean basin and forced by river runoff and influxes from the Atlantic Ocean and the Black Sea is used to obtain estimates of sea level rise in the region during the 21st century. Changes in temperature and salinity under the A2 emission scenario, which corresponds to a high level of anthropogenic gas concentration in the atmosphere, are investigated in the different sub-basins and are used to compute the steric sea level change in the region. Significant spatial variability is observed. This model projects a maximum steric sea level rise of 25 cm. The mean steric sea level rise value predicted is around 13 cm with lower values in the eastern Mediterranean and higher values at the western Mediterranean. Coastal sea level rise values are found to be smaller, although this is partly due to the smaller range of vertical integration in the computation of sea level changes. Warming and salinification of the intermediate waters are also predicted to occur simultaneously thus partly compensating each other. The effects of atmospheric pressure changes are added to the steric sea level obtained from the model giving up to 2 mbars and thus also compensating some of the thermal expansion. Circulation changes will in certain areas also add up to 6 cm of sea level rise. There is no predicted seasonal bias in the sea level rise indicating that the seasonal cycles will remain unaffected. These results are derived from a single model and therefore can only been seen as part of a methodological study. Similar investigations should be applied to a range of models and scenarios in order to obtain a range of the future sea level change in the Mediterranean basin and its associated uncertainties. [Copyright &y& Elsevier]

Highlights • Seven multi-decadal ocean simulations have been assessed for the Adriatic Sea. • Analysed simulations differ in resolution, forcing and coupling strategies. • Thermohaline properties and dynamic processes of the Adriatic Sea are better reproduced by coupled models. • All analysed models underrepresent dense water formation on the shelf. • Ocean model resolution and river forcing play a second-order role. Abstract A performance study of seven regional ocean configurations based on NEMO has been carried out for the Adriatic Sea over a common period (1980–2012). Assessed models differ in resolution, model physics, atmospheric forcing (forced vs. coupled models) and river discharges imposed within the Adriatic Sea. Models have been evaluated on the long-term temperature and salinity measurements in all of the Adriatic sub-basins, in particular within dense water collectors (Jabuka Pit and South Adriatic Pit) and dense water formation sites (northern and southern Adriatic). Adriatic-wide salinity content is mostly linked to the proper introduction of the overall water budget, rather than to the local river forcing. Forced models mostly overestimate temperature and salinity values. On average, coupled models better reproduce the thermohaline properties and processes, in particular the Adriatic-Ionian Bimodal Oscillating System (BiOS) reversals and its decadal variability. Wintertime heat losses are playing major role in defining the Adriatic Deep Water (ADW) transport rates in coupled models, while in forced models preconditioning in salinity is the most important factor. Further on, increase of resolution of the atmospheric forcing results in more realistic ocean behaviour, including dense water formation (DWF) in the complex coastal northern Adriatic. However, all models have large temperature biases and lower deep stratification at the dense water collector sites, indicating overall underrepresentation of the Adriatic DWF. Consequently, mixed-layer depth in the southern Adriatic is overestimated, reaching the bottom during some years. Ocean model resolution and river forcing seem to play a second-order role in defining the overall Adriatic-Ionian thermohaline properties, while inclusion of aerosol trend only slightly modified the BiOS reproduction. [ABSTRACT FROM AUTHOR]

The Strait of Gibraltar is a narrow and shallow channel that controls the Mediterranean Sea thermohaline and biogeochemical balances. Strong tidal currents significantly modulate exchanges across this strait and induce an intense vertical mixing, impacting both the Mediterranean Sea and the Atlantic Ocean on a climatic scale. However, the turbulent processes controlling the tidal mixing location, timing, and magnitude remain unclear. To fill this gap, we investigate tidal mixing at the Strait of Gibraltar in yearly twin tidal and non-tidal simulations from a regional configuration of the three-dimensional numerical model MITgcm, using a high spatial resolution around the Strait of Gibraltar (1/200°, 100 vertical levels). More specifically, we investigate the model turbulence closure scheme, based on a turbulent kinetic energy budget, and illustrate that vertical buoyancy fluxes should be preferred to diapycnal diffusivities as mixing indicators. In agreement with previous literature, we find that tides strongly intensify vertical mixing and motions within the Strait of Gibraltar. We then demonstrate that tidal mixing relies on two main ingredients: a sustained vertical shear of horizontal velocities and a local weakening of stratification. In the Mediterranean layer, the former drives diapycnal mixing near the seafloor and the latter in shallower areas above the prominent sills of the strait. We also evidence the frequent but irregular occurrences of static instabilities in the vicinity of these sills. In the Atlantic layer, both vertical shear and stratification are involved in diapycnal mixing that develops along the trail of the eastward internal bore released at the Camarinal sill. At high frequency, the local weakening of stratification results from convergence and divergence patterns in the vicinity of the Camarinal and Espartel sills, feeding recirculation cells between the Atlantic and Mediterranean layers. In addition, we highlight that diapycnal mixing mainly develops during the westward tidal phase in the Mediterranean layer and the eastward tidal phase in the Atlantic layer. We conclude by proposing a revised conceptual view of tidal mixing at the Strait of Gibraltar, where tidally-induced recirculation cells play an instrumental role in transforming the exchanged water masses. Overall, this study emphasizes the relevance of a realistic representation of both tides and abrupt topography to simulate the exchanges through the Strait of Gibraltar and argues for the use of a specific tidal mixing parameterization otherwise. • Tidal mixing mechanisms are investigated in a highresolution simulation of the Strait of Gibraltar. • Tidal convergence and divergence patterns, that feed recirculation cells, play an instrumental role in enhanced mixing at the Strait of Gibraltar. • Tides drive diapycnal mixing by enhancing vertical shear and weakening vertical stratification. • Accurate representation of both tides and abrupt topography is key for representing exchanges through the Strait of Gibraltar. [ABSTRACT FROM AUTHOR]

Abstract: A hindcast simulation in the Aegean–Levantine basins for the years 1960–2000 is performed, using an eddy resolving ocean model (1°/30). The model incorporates a 6-h atmospheric forcing provided by the ARPERA and captures the observed variability of the 40-years. The Eastern Mediterranean Transient (EMT) is the most prominent climatic event of the period. We investigate the impact of the atmospheric versus lateral forcing on the buoyancy content of the Aegean–Levantine basins. During the pre-EMT period, the basins’ buoyancy content is lowered by surface fluxes by about 1.5×10−8 m2 s−3 in the Aegean Sea, mostly related to surface heat loss, and lateral fluxes by about 0.9×10−8 m2 s−3, mostly related to salt flux, with the Levantine changes leading those of the Aegean. Furthermore, while long-term trends of surface and lateral inputs are preconditioning the changes in the Aegean stratification, it is the extreme heat loss pulses, related to the variability of the wind field that is controlling the formation processes by abruptly lowering the buoyancy content. Those events are possibly linked to an eastern Mediterranean bimodal atmospheric oscillation, with the anomalous surface heat fluxes shifting from the Levantine in the 1960s to the Aegean in the 1990s. The central Aegean due to its topography and thermohaline properties trigger events of excessive formation and producing the Aegean’s densest waters. During the EMT winters the central Aegean lower layers contain very dense waters, with σ Θ larger than 29.3kgm−3. These waters form the core of the water mass outflowing in the Eastern Mediterranean, after being mixed with ambient waters along their southward flow. The outflowing layer is characterized by density of 29.21kgm−3. The deepest parts of the NW Levantine is initially filled with the new water mass, which later spreads to the SE parts of the basin, flowing over the Eastern Mediterranean Ridge. [Copyright &y& Elsevier]

Abstract: This work proposes a new method to reconstruct and forecast surface Chlorophyll (Chl) from remotely sensed (SeaWiFS) data in the Alboran Sea, based on the correlation between zonal wind velocities and satellite Chl concentrations. First, the spatial and temporal variability of Chl and zonal wind have been characterized using standard statistics. Second, the annual cycle and trends are removed from the original time series and the residuals submitted to an EOF computation scheme. Then, the correlations between the amplitudes of the first temporal modes of Chl-wind couple have been quantified. Using the most highly correlated pair (Chl-zonal wind, with r=0.63), a simple linear relationship is proposed to reconstruct and forecast the Chl field. This forecasting method is more efficient than persistence for forecast horizons longer than 100days, with a mean correlation between original and predicted field of 0.73 as compared to 0.5 for persistence for all the year round. In partic\ular, this new method gives a 0.95 mean correlation for periods from 100 to 290days (while persistence gives 0.5). However, for a constant 8-days prediction horizon the persistence performs marginally better than the proposed method (0.79 vs. 0.68), giving some insight into the temporal scales of the features studied. These results may have significant implications for both short-term operational applications and seasonal forecasts. [Copyright &y& Elsevier]

Abstract: The contribution of atmospheric pressure and wind to the XXI century sea level variability in Southern Europe is explored under different climate change scenarios. The barotropic version of the HAMSOM model is forced with the output of the atmospheric ARPEGE model run under scenarios B1, A1B and A2. Additionally, a control simulation forced by observed SST, GHGs and aerosols concentrations for the period 1950–2000 and a hindcast forced by a dynamical downscalling of ERA40 for the period 1958–2001 are also run using the same models. The hindcast results have been validated against tide gauge observations showing good agreement with correlations around 0.8 and root mean square error of 3.2cm. A careful comparison between the control simulation and the hindcast shows a reasonably good agreement between both runs in statistical terms, which points towards the reliability of the modelling system when it is forced only by GHG and aerosols concentrations. The results for the XXI century indicate a sea level decrease that would be especially strong in winter, with trends of up to −0.8±0.1mm/year in the central Mediterranean under the A2 scenario. Trends in summer are small but positive (~0.05±0.04mm/yr), then leading to an increase in the amplitude of the seasonal cycle. The interannual variability also shows some changes, the most important being a widespread standard deviation increase of up to 40%. An increase in the frequency of positive phases of the NAO explains part of the winter negative trends. Also, an increase in the NAO variability would be responsible for the projected increase of the interannual variability of the atmospheric component of sea level. Conversely, the intra-annual variability (1–12months excluding the seasonal cycle) does not show significant changes. [Copyright &y& Elsevier]

Abstract: The sea level rise in the 1990s at the Mediterranean Sea as evidenced by satellite altimetry is studied with the aid of ocean models. Two barotropic two dimensional (2d) models and one three dimensional (3d) model are used. Both 2d models indicate that the contribution of direct atmospheric forcing causes localised trends of up to 2 mm/yr. The 3d model successfully describes the evolution in temperature of the upper and intermediate waters. However the salinity changes are not well described. The steric contribution of sea level rise during this period is in places in excess of 10 mm/yr. Notably oceanic circulation is also found to contribute to sea level trends by up to −3 mm/yr. Thus the observed sea level changes in the 1990s are better understood. The exceptional nature of the sea level behaviour in 1990s, especially in the eastern basin, when compared with previous decades is confirmed on the basis of both the 2d and the 3d models. [Copyright &y& Elsevier]

Abstract: Dense water formed over the continental shelf and cascading down the slope is responsible for shelf-slope exchanges in many parts of the world ocean, and transports large amounts of sediment and organic matter into the deep ocean. Here we perform numerical modeling experiments to investigate the impact of atmospheric interannual variability and climate change on dense water formation over the Gulf of Lions shelf, in the Northwestern Mediterranean Sea. Results obtained for a 140 years eddy-permitting simulation (1960–2100) performed over the whole Mediterranean Sea under IPCC A2 scenario forcings are used to force a regional eddy-resolving model of the Northwestern Mediterranean Sea. For the years selected in the present period, the quantity of dense water formed over and exported from the shelf is well correlated with atmospheric conditions, and dense water cascading is in agreement with available observations. During years colder than the average, most of the dense water formed over the shelf sinks into the deep ocean by cascading. During warmer years, dense water is mainly consumed by mixing with lighter surrounding water, and only a small quantity escapes the shelf, flowing along the coast without sinking. For the years selected in the future period, dense water formation over the shelf is strongly reduced, due to the stronger stratification of the water column. Most of the dense water formed is consumed over the shelf by mixing. A very small part escapes the shelf, flowing mainly in the surface layer: cascading practically disappears. The extrapolation of the results obtained for the selected years to the whole present and future periods suggests that volumes of dense water annually formed on the shelf, exported and cascading from the shelf are reduced by, respectively, 50%, 90% and 90% between the 20th century and the end of the 21st century. Uncertainties regarding our results are evaluated: the uncertainty due to the choice of the atmospheric forcing model is the most important, however, a decrease of cascading of at least 60% for the end of the 21st century compared to the present climate is obtained for every atmospheric model examined. [Copyright &y& Elsevier]