This study explores the long-term frequency variability of high-surge events (HSEs) in the North Adriatic, the so-called acqua alta, which, particularly during autumn, cause flooding of the historical city center of Venice. The period 1948–2008, when hourly observations of sea level are available, is considered. The frequency of HSEs is correlated with the 11 year solar cycle, solar maxima being associated with a significant increase in the October-November-December HSE frequency. The seasonal geopotential height pattern at 1000 hPa (storm surge pattern; SSP) associated with the increased frequency of HSEs is identified for the whole time period and found to be similar to the positive phase of the main variability mode of the regional atmospheric circulation (empirical orthogonal function 1; EOF1). However, further analysis indicates that solar activity modulates the spatial patterns of the atmospheric circulation (EOF) and the favorable conditions for HSE occurrence (SSP). Under solar maxima, the occurrence of HSEs is enhanced by the main mode of regional atmospheric variability, namely, a large-scale wave train pattern that is symptomatic of storm track paths over northern Europe. Solar minima reveal a substantially different and less robust SSP, consisting of a meridionally oriented dipole with a preferred southward path of storm track activity, which is not associated with any dominant mode of atmospheric variability during low-solar periods. It is concluded that solar activity plays an indirect role in the frequency of HSEs by modulating the spatial patterns of the main modes of atmospheric regional variability, the favorable patterns for HSE occurrence, and their mutual relationships, so that constructive interaction between them is enhanced during solar maxima and inhibited in solar minima.

The potential impact of climate change on port operations and infrastructures has received much less attention than the corresponding impact for beach systems. However, ports have always been vulnerable to weather extremes and climate change could enhance such occurrences at timescales comparable to the design lifetime of harbour engineering structures. The analysis in this paper starts with the main climatic variables affecting harbour engineering and exploitation. It continues with a review of the available projections for such variables first at global scale and then at a regional scale (Catalan coast in the western Mediterranean) as a study case for similar environments in the planet. The detailed assessment of impacts starts from downscaled projections for mean sea level and wave storms (wind not considered in the paper). This is followed by an analysis of the port operations and infrastructure performance that are relevant from a climate perspective. The key climatic factors here considered are relative sea level, wave storm features (height, period, direction and duration) and their combined effect, which is expected to produce the highest impacts. The paper ends with a discussion and some examples of analyses aiming at port adaptation to future climate change

The evolution of the upper water column in the Mediterranean Sea during more than 60 years is reconstructed in terms of few parameters describing the mixed layer and the seasonal thermocline. The analysis covers the period 1945–2011 using data from three public sources: MEDAR-MEDATLAS, World Ocean Database, MFS-VOS program. Five procedures for estimating the mixed layer depth are described, discussed and compared using the 20-year long time series of temperature profiles of the DYFAMED station in the Ligurian Sea. On this basis the so-called three segments profile model (which approximates the upper water column with three segments representing mixed layer, thermocline and deep layer) has been selected for a systematic analysis at Mediterranean scale. A widespread increase of the thickness and temperature of the mixed layer, increase of the depth and decrease of the temperature of the thermocline base have been observed in summer and autumn during the recent decades. It is shown that positive temperature extremes of the mixed layer and of its thickness are potential drivers of the mass mortalities of benthic invertebrates documented since 1983. Hotspots of mixed layer anomalies have been also identified. These results refine previous analyses showing that ongoing and future warming of upper Mediterranean is likely to increase mass mortalities by producing environmental conditions beyond the limit of tolerance of some benthic species.

For Northern Hemisphere extra-tropical cyclone activity, the dependency of a potential anthropogenic climate change signal on the identification method applied is analysed. This study investigates the impact of the used algorithm on the changing signal, not the robustness of the climate change signal itself. Using one single transientAOGCMsimulation as standard input for eleven state-of-the-art identification methods, the patterns of model simulated present day climatologies are found to be close to those computed from re-analysis, independent of the method applied. Although differences in the total number of cyclones identified exist, the climate change signals (IPCC SRES A1B) in the model run considered are largely similar between methods for all cyclones. Taking into account all tracks, decreasing numbers are found in the Mediterranean, the Arctic in the Barents and Greenland Seas, the mid-latitude Pacific and North America. Changing patterns are even more similar, if only the most severe systems are considered: the methods reveal a coherent statistically significant increase in frequency over the eastern North Atlantic and North Pacific.We found that the differences between the methods considered are largely due to the different role of weaker systems in the specific methods.

This study analyzes large positive and negative storm surges along the Mediterranean coast in a 7-member climate model ensemble covering the period 1951-2050 under the A1B emission scenario. A hydro-dynamical shallow water model (HYPSE, Hydrostatic Padua Sea Elevation model) is driven by 6-hourly meteorological fields produced by the state-of-the-art global and regional climate models that have been used in the CIRCE fp6 project (Climate Change and Impact Research: the Mediterranean Environment). Model validation is based on the comparison of a model hindcast (1958-2001) and climate simulations with observed sea level (SL) values at 21 tide gauges. The accuracy of the models in reproducing large positive and negative storm surges appears to depend primarily on the quality of the atmospheric forcing (which is mainly related to their space resolution). Also the resolution of the hydro-dynamical model is somehow relevant along some stretches of the coastline. Climate signal is computed as the difference between the surge statistics in the 2021-2050 and 1971-2000 periods. The choice of the global climate simulation, which is used for the boundary conditions of the regional climate models, is shown to be the largest source of uncertainty for the assessment of the climate change signal. Other, less relevant, sources of uncertainty are the choice of the regional climate model and that of the hydro-dynamical model resolution. In spite of these uncertainties, the model ensemble mean shows a modest (about -. 5%), but clear and widespread decrease of the amplitude of both positive and negative large storm surges along the coast of the Mediterranean Sea. However, increase of mean SL and land subsidence (which are not considered in this study) might increase significantly the hazard posed by coastal floods in spite of the likely attenuation of storminess that is caused by climate change in the Mediterranean Sea

This chapter aims at introducing the main topics in the Mediterranean circulation research and a general description on the Mediterranean Sea variability. Its scope is to provide information that is important for a comprehensive view of the most relevant issues concerning climate, which is composed by a coupling between atmosphere and sea. The chapter describes data, research results and key findings that have been reported in the most recent literature about the Mediterranenan Sea circulation. The issue about sea level is considered in chapter 4. The chapter includes also discussion of the main open issues in the Mediterranean Sea research in the concluding secion.

In this chapter regional climate conditions are described in terms of the properties and behavior of the atmospheric circulation over and around the Mediterranean region (MR). The aim is to study the relationships between the atmospheric circulation and the surface environment and identify key dynamical interactions that are involved. In this sense the content of this chapter belongs to the general topic of synoptic climatology (see Huth et al. 2009 for a short discussion). Specifically this chapters describes the teleconnection patterns influencing the MR (section 1), the characteristics of the cyclones in the MR and their links to large-scale patterns (section 2), and the synoptic circulation conditions leading to temperature and precipitation extremes (section 3 and 4, respectively). Finally, local winds, wind extremes and some specific effects they induce (dust storms, storm surges, waves) are discussed.

This study concerns the analysis of a 37-year long directional wave time series recorded since 1979 at the CNR-ISMAR oceanographic research tower, located in the Northern Adriatic Sea. The length of the time series allows to describe the wave climate in the North Adriatic and to identify trends and links with large-scale climate patterns. The northern part of the Adriatic Sea is characterized by two main wind and correspondingly wave regimes, strongly forced by the regional orography: the long-fetch south-easterly ‘sirocco’ and the short-fetch strong north-easterly ‘bora’ wind generated waves, blowing along the major and minor axis of the basin, respectively. Bora is the most frequent regime, but high waves are mostly associated to sirocco. A clear decrease of the significant wave height 99th percentile is evident, paralleled by a smaller, but distributed along the annual cycle, increase of the 50th and 75th ones. The estimated trend of the frequency of events above a certain threshold confirms an increase of the average storm frequency, with a shift from both the lower and the higher to the central part of the distribution, paralleled by a decrease of the maximum Hs values. In particular, a distributed decrease of the bora significant wave height is recognized. For sirocco the tendency is less pronounced, but with an evident increase of the frequency of the mean values. The high sensitivity of this particular area to even small variations of large-scale climate allows to explore possible links of the local wave, hence wind, activity with large-scale Northern Hemisphere circulation patterns or weather regimes. Our main interest is on the storm tracks and jet stream location/intensity over vast areas, which led us to choose four reference patterns: the North Atlantic Oscillation and the East Atlantic (EA), EA/Western Russia and Scandinavian patterns.

Soreq (Israel) and Corchia (central Italy) Caves are located 2500km far apart along the Mediterranean winter-storm track and are ideally suited for investigating past variations of winter rainfall in the Mediterranean region. Analyses of speleothem δ18O records from both caves for the period between ca. 7 to 4 ka BP show some striking similarities for the ca. 6 and 4ka interval, but lack agreement between ca. 7 to 6kaBP. Two prominent isotopic excursions, argued to reflect relatively drier conditions, are centred at ca. 5.6 and ca. 5.2 ka. The 5.2 ka event lasts less than a century, whereas the 5.6ka event extends from ca. 5.7 to 5.4 ka. A period of progressive drying is also apparent from ca. 5 to 4ka. Another prominent event, reflecting wetter conditions, is recorded in both records at ca. 5.8ka and seems to last several decades. The 5.6 and 5.2ka events occurred within a period of higher deposition of haematite-stained grains in cores of the sub-polar North Atlantic, and correlation with the wind strength proxy record from Hólmsá loess profile in Iceland suggests that rainfall reduction was related to a reduced vapour advection from Atlantic towards the Mediterranean connected to northward shift in the Westerlies. A comparison with Alpine records, including the Spannagel Cave isotope record, suggests that dry events recorded at Soreq and Corchia caves may correspond to wetter (lake high stands) and cooler (glacier expansion) conditions in the Alpine region, indicating complex regional climate re-organization

This study describes characteristics and evolution of the residual of the Earth energy budget (EB) individual components and the implied meridional transports during the twentieth century. This analysis considers two ensembles of AMIP-like experiments (Atmospheric Model Intercomparison Project) with prescribed evolution of sea surface temperature and sea ice concentration (SST-SIC), greenhouse gases (GHG), anthropogenic and volcanic aerosols over the entire twentieth century: ERA-20CM and ECHAM5-HAM model simulations. With the latter, additional sensitivity experiments are carried out by constraining either SST-SIC or aerosols to climatological values. The two models provide compatible estimates of the EBs and implied transport absolute values in recent decades. They are not in agreement in terms of global scale evolution: in the 1970s ERA-20CM shows a fast transition from negative to positive EBs at top of atmosphere (TOA) that is not found in ECHAM5-HAM. Climatological SST-SIC sensitivity experiments evidence that the aerosol forcing affects TOA and surface EBs by setting up an inter-hemispheric gradient after 1960. This is also reflected by an increased total transport in the Northern Hemisphere, while decreased in the Southern Hemisphere. ERA-20CM shows no evidence of a similar aerosol forcing. Sensitivity experiments with fixed pre-industrial aerosols show that transient SST are responsible for irregular spatio-temporal anomalies of surface and atmospheric EBs and transports. Surface and atmospheric anomalies oppose each other, and transient SSTs do not influence the EB changes at TOA. Impact of transient SST and GHG forcing on EBs and implied transports are robust across the two models.

This study analyzes the evolution of the Hadley Circulation (HC) during the twentieth century in ERA-20CM (AMIP-experiment) and ERA-20C (reanalysis). These two recent ECMWF products provide the opportunity for a new analysis of the HC trends and of their uncertainties. Further, the effect of sea surface temperature forcing (including its uncertainty) and data assimilation are investigated. Also the ECMWF reanalysis ERA-Interim, for the period 1979–2010, is considered for a complementary analysis. Datasets present important differences in characteristics and trends of the HC. In ERA-20C HC is weaker (especially the Southern Hemisphere HC) and the whole Northern Hemisphere HC is located more southward than in ERA-20CM (especially in the boreal summer). In ERA-Interim HC is stronger and wider than both other simulations. In general, the magnitude of trends is larger and more statistically significant in ERA-20C than in ERA-20CM. The presence of large multidecadal variability across twentieth century raises doubts on the interpretation of recent behavior, such as the onset of sustained long term trends, particularly for the HC strength. In spite of this, the southward shift of the Southern Edge and widening of the Southern Hemisphere HC appear robust features in all datasets, and their trends have accelerated in the last three decades, but actual expansion rates remain affected by considerable uncertainty. Inconsistencies between datasets are attributed to the different reproduction of the links between the HC width and factors affecting it (such as mean global temperature, tropopause height, meridional temperature contrast and planetary waves), which appear more robust in ERA-20CM than in ERA-20C, particularly for the two latter factors. Further, in ERA-Interim these correlations are not statistically significant. These outcomes suggest that data assimilation degrades the links between the HC and features influencing its dynamics.

Scenario climate projections for extreme marine storms producing storm surges and wind waves are very important for the northern flat coast of the Adriatic Sea, where the area at risk includes a unique cultural and environmental heritage, and important economic activities. This study uses a shallow water model and a spectral wave model for computing the storm surge and the wind wave field, respectively, from the sea level pressure and wind fields that have been computed by the RegCM regional climate model. Simulations cover the period 1961–1990 for the present climate (control simulations) and the period 2071–2100 for the A2 and B2 scenarios. Generalized Extreme Value analysis is used for estimating values for the 10 and 100 year return times. The adequacy of these modeling tools for a reliable estimation of the climate change signal, without needing further downscaling is shown. However, this study has mainly a methodological value, because issues such as interdecadal variability and intermodel variability cannot be addressed, since the analysis is based on single model 30-year long simulations. The control simulation looks reasonably accurate for extreme value analysis, though it overestimates/underestimates the frequency of high/low surge and wind wave events with respect to observations. Scenario simulations suggest higher frequency of intense storms for the B2 scenario, but not for the A2. Likely, these differences are not the effect of climate change, but of climate multidecadal variability. Extreme storms are stronger in future scenarios, but differences are not statistically significant. Therefore this study does not provide convincing evidence for more stormy conditions in future scenarios.

The Hadley circulation (HC) extent and strength are analyzed in a wide range of simulated climates from the Last Glacial Maximum to global warming scenarios. Motivated by HC theories, we analyze how the HC is influenced by the subtropical stability, the near-surface meridional potential temperature gradient, and the tropical tropopause level. The subtropical static stability accounts for the bulk of the HC changes across the simulations. However, since it correlates strongly with global mean surface temperature, most HC changes can be attributed to global mean surface temperature changes. The HC widens as the climate warms, and it also weakens, but only robustly so in the Northern Hemisphere. On the other hand, the Southern Hemisphere strength response is uncertain, in part because subtropical static stability changes counteract meridional potential temperature gradient changes to various degrees in different models, with no consensus on the response of the latter to global warming.

This study aims at discussing evolution of Sea Level (SL) in the Northern Adriatic Sea for the 20th and 21st century. A Linear Regression Model (LRM) which aims at describing the effect of regional processes, is built and validated. This LRM computes the North Adriatic mean SL variations using three predictors: the Mean Sea Level Pressure (MSLP) in the Gulf of Venice, the mean Sea Temperature (ST) of the water column in the South Adriatic and the Upper Level Salinity (ULS) in the central part of the basin. SL data are provided by monthly values recorded at 7 tide gauges distributed along the Italian and Croatian coasts (available at the PSMSL, Permanent Service of Mean Sea Level). MSLP data are provided by the EMULATE data set. Mediterranean ST and ULS data are extracted from the MEDATLAS/2002 database. The study shows that annual SL variations at Northern Adriatic stations are very coherent, so that the Northern Adriatic SL can be reconstructed since 1905 on the basis of only two stations: Venice and Trieste. The LRM is found to be robust, very successful at explaining interannual SL variations and consistent with the physical mechanisms responsible for SL evolution. Results show that observed SL in the 20th century has a large trend, which cannot be explained by this LRM, and it is interpreted as the superposition of land movement and a remote cause (such as polar ice melting). When the LRM is used with the MSLP, ST and ULS from climate model projections for the end of the 21st century (A1B scenario), it produces an SL rise in the range from 2.3 to 14.1. cm, with a best estimate of 8.9. cm. However, results show that the behavior of the remotely forced SL rise is the main source of future SL uncertainty and extrapolating its present trend to the future would expand the range of SL uncertainty from 14 to 49. cm.

Satellite data show a steady increase, in the last decades, of the surface temperature (upper few millimetres of the water surface) of the Mediterranean Sea. Reports of mass mortalities of benthic marine invertebrates increased in the same period. Some local studies interpreted the two phenomena in a cause-effect fashion. However, a basin-wide picture of temperature changes combined with a systematic assessment on invertebrate mass mortalities was still lacking. Both the thermal structure of the water column in the Mediterranean Sea over the period 1945-2011 and all documented invertebrate mass mortality events in the basin are analysed to ascertain if: 1- documented mass mortalities occurred under conditions of positive temperature trends at basin scale, and 2- atypical thermal conditions were registered at the smaller spatial and temporal scale of mass mortality events. The thermal structure of the shallow water column over the last 67 years was reconstructed using data from three public sources: MEDAR-MEDATLAS, World Ocean Database, MFS-VOS programme. A review of the mass mortality events of benthic invertebrates at Mediterranean scale was also carried out. The analysis of in situ temperature profiles shows that the Mediterranean Sea changed in a non-homogeneous fashion. The frequency of mass mortalities is increasing. The areas subjected to these events correspond to positive thermal anomalies. Statistically significant temperature trends in the upper layers of the Mediterranean Sea show an increase of up to 0.07°C/yr for a large fraction of the basin. Mass mortalities are consistent with both the temperature increase at basin scale and the thermal changes at local scale, up to 5.2°C. Our research supports the existence of a causal link between positive thermal anomalies and observed invertebrate mass mortalities in the Mediterranean Sea, invoking focused mitigation initiatives in sensitive areas.

Climate change impact on storm surge regime is of great importance for the safety and maintenance of Venice. In this study a future storm surge scenario is evaluated using new high resolution sea level pressure and wind data recently produced by EC-Earth, an Earth System Model based on the operational seasonal forecast system of the European Centre for Medium-Range Weather Forecasts (ECMWF). The study considers an ensemble of six 5 yr long simulations of the rcp45 scenario at 0.25 resolution and compares the 2094-2098 to the 2004-2008 period. EC-Earth sea level pressure and surface wind fields are used as input for a shallow water hydrodynamic model (HYPSE) which computes sea level and barotropic currents in the Adriatic Sea. Results show that a high resolution climate model is needed for producing realistic values of storm surge statistics and confirm previous studies in that they show little sensitivity of storm surge levels to climate change. However, some climate change signals are detected, such as increased persistence of high pressure conditions, an increased frequency of windless hour, and a decreased number of moderate windstorms

The Mediterranean countries are experiencing important challenges related to the water cycle including water shortages and floods, extreme winds and ice/snow storms that impact critically the socioeconomic vitality in the area (causing damage to property; threatening lives; affecting the energy and transportation sectors, etc.). There are gaps in our understanding of the Mediterranean water cycle and its dynamics, which include the variability of the Mediterranean Sea water budget and its feedback on the variability of the continental precipitation through air/sea interactions, the impact of precipitation variability on aquifer recharge, river discharge, soil water content and vegetation characteristics specific of the Mediterranean basin and the mechanisms that control the location and intensity of heavy precipitating systems which often produce floods. The HyMeX (Hydrological cycle in the Mediterranean Experiment) programme is a 10-year concerted experimental effort at the international level aiming at advancing the scientific knowledge of the water cycle variability in all compartments (land, sea and atmosphere) and at various time and spatial scales. It also aims at improving the processes-based models needed for forecasting hydro-meteorological extremes and the models of the regional climate system needed for predicting and planning adaptation strategies against the impacts of climate variability and change and human activity on the frequency and severity of hydro-meteorological hazards in the Mediterranean basin.

The IMILAST intercomparison experiment was initiated involving 15 commonly used detection and tracking algorithms for extratropical cyclones reveals those cyclone characteristics that were robust between different schemes and those that differed considerably. All participating groups computed cyclone tracks for the same period using the same input, such as the European Center for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim) dataset on whose results the first activity of the experiment was based. Space-time resolution of the input data had a significant impact on cyclone statistics. The experiment also revealed that high resolution was essential to help capture the full life cycles of cyclones and to ensure that small cyclonic windstorms were identified. Researchers used 1.5° spatial resolution and 6-hourly temporal resolution except for one method that used 12-hourly data for a 20-yr period ranging from January 1, 1989 to March 31, 2009.

The Mediterranean basin is the largest world area having specific climatic conditions suitable for olive cultivation, which has a great socio-economic importance in the region. However, the Mediterranean might be particularly affected by climate change, which could have extensive impacts on ecosystems and agricultural production. This work focussed on the climate change impact on olive growing in the Mediterranean region considering the possible alterations of cultivable areas, phenological dates, crop evapotranspiration and irrigation requirements. Monthly climate data, with a spatial resolution of 0.25°×0.25° (latitude by longitude), have been derived from Regional Climate Models driven by ECHAM5 for the A1B scenario of the Special Report on Emissions Scenarios (SRES). The data used in the analysis represented two time periods: (i) present, called year 2000 (average values for the period 1991-2010), and (ii) future, called year 2050 (average values for the period 2036-2065). The areas suitable for olive cultivation were determined using the temperature requirements approach known as the Agro Ecological Zoning method. Crop evapotranspiration and irrigation requirements were estimated following the standard procedure described in the FAO Irrigation and Drainage Paper 56. Results showed that the potentially cultivable areas for olive growing are expected to extend northward and at higher altitudes and to increase by 25% in 50 years. The olive flowering is likely to be anticipated by 11±3 days and crop evapotranspiration is expected to increase on average by 8% (51±17mmseason-1). Net irrigation requirements are predicted to increase by 18.5% (70±28mmseason-1), up to 140mm in Southern Spain and some areas of Algeria and Morocco. Differently, effective evapotranspiration of rainfed olives could decrease in most areas due to expected reduction of precipitation and increase of evapotranspirative demand, thus making it not possible to keep rainfed olives' production as it is at present

This introductory chapter of The Mediterranean Sea: Temporal Variability and Spatial Patterns, Geophysical Monograph 202 provides a general outline of the book. The book collects eight original research articles describing new results in the study of the Mediterranean Sea physical properties. It is meant to be an important and original contribution to the knowledge of the phenomena that regulate the oceanography of the basin. Furthermore, the book is a valuable tool for those not directly involved in Mediterranean studies who want to use the Mediterranean as a basin for processes of interest for the global ocean and climate. The studies in the book can be regarded individually or as parts of an integrated dissertation on spatial patterns and temporal variability of the Mediterranean Sea.

This chapter introduces the main topics in current Mediterranean climate research and contains a general description of the Mediterranean Climate. Its aim is to provide essential information and a comprehensive view. It also anticipates the data, research results and key findings that are presented in much more detail in the book chapters, to which the reader is directed for extensive discussion. In this chapter the regional climate system is introduced considering different time scales, from paleo-climate to centennial climate projection, attempting a seamless approach to the description of the evolution from past to future climate, and including not just the atmospheric variables but also the oceanic and land components. This chapter includes a discussion of the main open issues in the Mediterranean climate research and also briefly presents social-economic problems and vulnerabilities that are specific to the Mediterranean region.

The Mediterranean is expected to be one of the most prominent and vulnerable climate change "hotspots" of the twenty-first century, and the physical mechanisms underlying this finding are still not clear. Furthermore, complex interactions and feedbacks involving ocean-atmosphere-land-biogeochemical processes play a prominent role in modulating the climate and environment of the Mediterranean region on a range of spatial and temporal scales. Therefore, it is critical to provide robust climate change information for use in vulnerability-impact-adaptation assessment studies considering the Mediterranean as a fully coupled environmental system. The Mediterranean Coordinated Regional Downscaling Experiment (Med-CORDEX) initiative aims at coordinating the Mediterranean climate modeling community toward the development of fully coupled regional climate simulations, improving all relevant components of the system from atmosphere and ocean dynamics to land surface, hydrology, and biogeochemical processes. The primary goals of Med-CORDEX are to improve understanding of past climate variability and trends and to provide more accurate and reliable future projections, assessing in a quantitative and robust way the added value of using high-resolution and coupled regional climate models. The coordination activities and the scientific outcomes of Med-CORDEX can produce an important framework to foster the development of regional Earth system models in several key regions worldwide. ©2016 American Meteorological Society.

The objective of this chapter is to make a review on the state of the art of regional climate modeling over the Mediterranean. Two main parts are developed. The first one is devoted to atmospheric parameters and the basic performance of both global and regional climate models in simulating the Mediterranean climate. We focus on the added-value that high-resolution models can bring in terms of surface winds, surface hydrology and intense rainfall events. The second part deals with the general circulation of the Mediterranean Sea. We make a general review on the performance of current oceanic models of both coarse resolution (about 1 to 2 degrees) and high resolution (about 1/8 to 1/16 degrees). A comparison among a few coupled models gives a good assessment about our current skill in modeling the Mediterranean climate.

Harbours are essential infrastructures for economic activity that are susceptible to impacts from climate change driven processes, like sea level rise (SLR), or alterations in wave patterns. In this paper, the impact of climate change on wave agitation in ports (oscillations due to wind waves) and, therefore, on port operability is analyzed. This is carried out through a numerical model suite, considering the RCP8.5 scenario to project changes in wave fields, and three values of SLR. The study is particularized for the port of Barcelona (NW Mediterranean), but the used methodology can be applied to other harbours. Results suggest that changes due only to waves will be minimal and with a general trend to slightly decrease wave agitation. On the contrary, the effect of SLR and the associated increase of water depth will favor the penetration of waves within the harbour, leading to a certain reduction of port operability, the magnitude of which will depend on the SLR value. However, the complexity of wave patterns within the harbours, due to multiple reflections of waves on port structures, implies that the reduction of operability strongly varies according to the position and orientation of the berthing zones inside the

Extreme events, such as wave-storms, need to be characterized for coastal infrastructure design purposes. Such description should contain information on both the univariate behaviour and the joint-dependence of storm-variables. These two aspects have been here addressed through generalized Pareto distributions and hierarchical Archimedean copulas. A non-stationary model has been used to highlight the relationship between these extreme events and non-stationary climate. It has been applied to a Representative Concentration Pathway 8.5 Climate-Change scenario, for a fetch-limited environment (Catalan Coast). In the non-stationary model, all considered variables decrease in time, except for storm-duration at the northern part of the Catalan Coast. The joint distribution of storm variables presents cyclical fluctuations, with a stronger influence of climate dynamics than of climate itself.

The Mediterranean storm track constitutes a well-defined branch of the North Hemisphere storm track and is characterised by small but intense features and frequent cyclogenesis. The goal of this study is to assess the level of consensus among cyclone detection and tracking methods (CDTMs), to identify robust features and to explore sources of disagreement. A set of 14 CDTMs has been applied for computing the climatology of cyclones crossing the Mediterranean region using the ERA-Interim dataset for the period 1979-2008 as common testbed. Results show large differences in actual cyclone numbers identified by different methods, but a good level of consensus on the interpretation of results regarding location, annual cycle and trends of cyclone tracks. Cyclogenesis areas such as the north-western Mediterranean, North Africa, north shore of the Levantine basin, as well as the seasonality of their maxima are robust features on which methods show a substantial agreement. Differences among methods are greatly reduced if cyclone numbers are transformed to a dimensionless index, which, in spite of disagreement on mean values and interannual variances of cyclone numbers, reveals a consensus on variability, sign and significance of trends. Further, excluding 'weak' and 'slow' cyclones from the computation of cyclone statistics improves the agreement among CDTMs. Results show significant negative trends of cyclone frequency in spring and positive trends in summer, whose contrasting effects compensate each other at annual scale, so that there is no significant long-term trend in total cyclone numbers in the Mediterranean basin in the 1979-2008 period

Providing a reliable, accurate, and fully informative storm surge forecast is of paramount importance for managing the hazards threatening coastal environments. Specifically, a reliable probabilistic forecast is crucial for the management of the movable barriers that are planned to become operational in 2018 for the protection of Venice and its lagoon. However, a probabilistic forecast requires multiple simulations and a considerable computational time, which makes it expensive in real-time applications. This paper describes the ensemble dressing method, a cheap operational flood prediction system that includes information about the uncertainty of the ensemble members by computing it directly from the meteorological input and the local spread distribution, without requiring multiple forecasts. Here, a sophisticated error distribution form is developed, which includes the superposition of the uncertainty caused by inaccuracies of the ensemble prediction system, which depends on surge level and lead time, and the uncertainty of the meteorological forcing, which is described using a combination of cross-basin pressure gradients. The ensemble dressing is validated over a 3-month-long period in the year 2010, during which an exceptional sequence of storm surges occurred. Results demonstrate that this computationally cheap method can provide an acceptably realistic estimate of the uncertainty

An analysis of the climate change signal for seasonal temperature and precipitation over the Northern Adriatic region is presented here. We collected 43 regional climate simulations covering the target area, including experiments produced in the context of the PRUDENCE and ENSEMBLES projects, and additional experiments produced by the Swedish Meteorological and Hydrological Institute. The ability of the models to simulate the present climate in terms of mean and interannual variability is discussed and the insufficient reproduction of some features, such as the intensity of summer precipitation, are shown. The contribution to the variance associated with the intermodel spread is computed. The changes of mean and interannual variability are analyzed for the period 2071–2100 in the PRUDENCE runs (A2 scenario) and the periods 2021–2050 and 2071–2100 (A1B scenario) for the other runs. Ensemble results show a major warming at the end of the 21st century. Warming will be larger in the A2 scenario (about 5.5 K in summer and 4 K in winter) than in the A1B. Precipitation is projected to increase in winter and decrease in summer by 20% (+0.5 mm/day and 1 mm/day over the Alps, respectively). The climate change signal for scenario A1B in the period 2021–2050 is significant for temperature, but not yet for precipitation. In summer, interannual variability is projected to increase for temperature and for precipitation. Winter interannual variability change is different among scenarios. A reduction of precipitation is found for A2, while for A1B a reduction of temperature interannual variability is observed.

The region of Apulia, which is located in the south-east tip of the Italian Peninsula, has a typical Mediterranean climate with mild winters and hot-dry summers. Agriculture, an important sector of its economy, is potentially threatened by future climate change. This study describes the evolution of seasonal temperature and precipitation from the recent past to the next decades and estimates future potential impacts of climate change on three main agricultural products: wine, wheat and olives. Analysis is based on instrumental data, on an ensemble of climate projections and on a linear regression model linking these three agricultural products to seasonal values of temperature and precipitation. In Apulia, precipitation and temperature time series show trends toward warmer and marginally drier conditions during the whole analyzed (1951–2005) period: 0.18 °C/decade in mean annual minimum temperature and −14.9 mm/decade in the annual total precipitation. Temperature trends have been progressively increasing and rates of change have become noticeably more intense during the last 25 years of the twentieth century. Model simulations are consistent with observed trends for the period 1951–2000 and show a large acceleration of the warming rate in the period 2001–2050 with respect to the period 1951–2000. Further, in the period 2001–2050, simulations show a decrease in precipitation, which was not present in the previous 50 years. Wine production, wheat and olive harvest records show large inter-annual variability with statistically significant links to seasonal temperature and precipitation, whose strength, however, strongly depends on the considered variables. Linear regression analysis shows that seasonal temperature and precipitation variability explains a small, but not negligible, fraction of the inter-annual variability of these crops (40, 18, 9 % for wine, olives and wheat, respectively). Results (which consider no adaptation of crops and no fertilization effect of CO2) suggest that evolution of these seasonal climate variables in the first half of the twenty-first century could decrease all considered variables. The most affected is wine production (−20 ÷ −26 %). The effect is relevant also on harvested olives (−8 ÷ −19 %) and negligible on harvested wheat (−4 ÷ −1 %).

This paper discusses present characteristics and trends of marine storminess in the Northern Adriatic. It merges oceanographic and meteorological aspects, by considering storm surges, wind waves and the atmospheric cyclones that cause them. The paper describes the dynamics of these three processes, the different role of south-easterly (Sirocco) and easterly (Bora) wind regimes. The specific characteristics of cyclones producing severe marine storms in terms of location where cyclogenesis occurs, trajectories and intensity, are compared with those of generic cyclones crossing northern Italy. It is shown that cyclones producing high waves and surges have different characteristics and their lists overlap only partially. However, both high wave and surge events have a similar annual cycle, with maximum activity in November and hardly any event in summer (June-July-August). The trends of severe high wave and surge events are discussed (various thresholds are considered) and they are shown to be consistent. Timeseries, which show large interannual variability and very little overall tendencies on multi-decadal time scale, are suggestive of progressively milder storms during the second half of the 20th century.

The link between winter (December-January-February) precipitation events at 15 Mediterranean coastal locations and synoptic features (cyclones and Northern Hemisphere teleconnection patterns) is analyzed. A list of precipitation events has been produced; q percentile thresholds (Thq) and corresponding frequency Nq (for q equal to 25, 50, 90 and 98) have been considered. A negative trend has been detected in total precipitation and N50 at many locations, while no significant trend in N25, N90 and N98 has been found. The negative phase of the North Atlantic Oscillation (NAO) and the East Atlantic/West Russia pattern (EAWR) compete for exerting the largest influence on the frequency of the 25th, 50th and 90th percentiles, with EAWR and NAO exerting their largest influence in the central and western Mediterranean areas, respectively. All percentiles show a similar behavior except for the 98th percentile, which shows no convincing link to any teleconnection pattern. The cyclone tracks that are associated with precipitation events have been selected using the ERA-40 reanalysis data, and a strong link between intense precipitation and cyclones is shown for all stations. In general, the probability of detecting a cyclone within a distance of 20 from each station increases with the intensity of the precipitation event and decreases with the duration of a dry period. The origin and track of cyclones producing intense precipitation differ among different areas. When precipitation occurs in the northwestern Mediterranean, cyclones are generally either of Atlantic origin or secondary cyclones associated with the passage of major cyclones north of the Mediterranean Basin, while they are mostly generated inside the region itself for events at the eastern Mediterranean coast. An important fraction of intense events in the southern areas is produced by cyclones that are generated over northern Africa. The analysis of sea level pressure and geopotential height at 500 hPa highlights the important role of cyclone depth, circulation strength, surrounding synoptic condition, and of slow speed of the cyclone center for producing intense precipitation events

The Mediterranean region contains a diverse and interesting climate ranging from areas with permanent glaciers to areas of subtropical, semiarid regions. The region is potentially sensitive to climate change and its progress has environmental, social, and economic implications within and beyond the region. Produced by the Mediterranean Climate Variability and Predictability Research Networking Project, this book reviews the evolution of the Mediterranean climate over the past two millennia with projections further into the twenty-first century as well as examining in detail various aspects of the Mediterranean region’s climate including evolution, atmospheric variables, and oceanic and land elements. Integrated with this, the book also considers the social and economic problems or vulnerabilities associated with the region. Written and reviewed by multiple researchers to ensure a high level of information presented clearly, Mediterranean Climate Variables will be an invaluable source of information for geologists, oceanographers, and anyone interested in learning more about the Mediterranean climate.

Future climate change over the Mediterranean area is investigated by means of climate model simulations covering the 21st century that take into account different anthopogenic greenhouse gases emission scenarios. This chapter first gives some new insights on these projections coming from the use of new methodologies including the coupling at the regional scale of the atmospheric component to a Mediterranean sea component. A synthesis of the expected changes on key aspects of the Mediterranean regional climate, obtained with a wide range of models and downscaling methodologies, is then presented. This includes an overview of expected changes in the mean climate and climate extremes, but also possible changes in Mediterranean sea temperature, salinity, circulation, water and heat budgets, and sea level. The chapter ends with some advanced results on the way to deal with uncertainties on climate projections and some discussion on the confidence that we can attribute to these projections.

This editorial analyzes the evolution of the climate of the Venetian region on the basis of the contributions presented at a workshop that was organized in Venice (27-29 October 2008) by CORILA (COnsorzio RIcerche LAguna) and published in this special issue. The workshop has considered past and future evolution of the regional climate, sea level, storminess, and has allowed to widely discuss important scientific results and to identify existing gaps in the present knowledge. In the Venetian plane an unprecedented warming (3.2oC/century) and a moderate decrease of annual precipitation (-3%/century) are expected, with no analogy in the past 250 years during which there was no sustained centennial trend. The understanding of past sea level evolution is in part problematic. The analysis of tide gauges in Venice and Trieste suggests a centennial trend of relative sea level rise (about 1.1mm/year) comparable to, but smaller than, the global sea level trend. However, past relative sea level in Venice has been strongly affected by tectonic motions and isostatic adjustment. If their estimated effects are subtracted from the tide gauge observation, the sea surface height in Venice would show a centennial trend (0.3mm/year) that is much smaller than the global value. Unless a physical explanation for this low value is found, estimates of vertical land motions for this century need to be reconsidered. Future evolution of sea level is uncertain. Glaciers and ice sheet melting, its regional implications, regional steric effects associated with changes of temperature and salinity are all expected to be important in future and are not adequately known. A large future halosteric contribution is peculiar of the Mediterranean Sea, where future increased salinity and consequent contraction of the water column could compensate for water mass addition and thermosteric expansion. The time series of storminess is dominated by large interannual and interdecadal variability and there is no evidence of its past or future changes on centennial time scale. Relative sea level trends are very likely to be the main cause of future changes of flood frequency and height, which will, anyway, continue being strongly affected by interannual and interdecadal fluctuations.

In the Adriatic Sea, storm surges present a significant threat to Venice and to the flat coastal areas of the northern coast of the basin. Sea level forecast is of paramount importance for the management of daily activities and for operating the movable barriers that are presently being built for the protection of the city. In this paper, an EPS (ensemble prediction system) for operational forecasting of storm surge in the northern Adriatic Sea is presented and applied to a 3-month-long period (October–December 2010). The sea level EPS is based on the HYPSE (hydrostatic Padua Sea elevation) model, which is a standard single-layer nonlinear shallow water model, whose forcings (mean sea level pressure and surface wind fields) are provided by the ensemble members of the ECMWF (European Center for Medium-Range Weather Forecasts) EPS. Results are verified against observations at five tide gauges located along the Croatian and Italian coasts of the Adriatic Sea. Forecast uncertainty increases with the predicted value of the storm surge and with the forecast lead time. The EMF (ensemble mean forecast) provided by the EPS has a rms (root mean square) error lower than the DF (deterministic forecast), especially for short (up to 3 days) lead times. Uncertainty for short lead times of the forecast and for small storm surges is mainly caused by uncertainty of the initial condition of the hydrodynamical model. Uncertainty for large lead times and large storm surges is mainly caused by uncertainty in the meteorological forcings. The EPS spread increases with the rms error of the forecast. For large lead times the EPS spread and the forecast error substantially coincide. However, the EPS spread in this study, which does not account for uncertainty in the initial condition, underestimates the error during the early part of the forecast and for small storm surge values. On the contrary, it overestimates the rms error for large surge values. The PF (probability forecast) of the EPS has a clear skill in predicting the actual probability distribution of sea level, and it outperforms simple “dressed” PF methods. A probability estimate based on the single DF is shown to be inadequate. However, a PF obtained with a prescribed Gaussian distribution and centered on the DF value performs very similarly to the EPS-based PF