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The Baltic Sea coasts hold huge potential for summer beaching in the 21st century. The appropriate temperature and precipitation regime are prior to Mediterranean Sea climatic conditions which become too hot with regular heat waves in summer. The originally designed method allows to evaluate more "precise" UTCI values (in °C) using averaged monthly data of meteorological variables (air temperature, humidity, wind velocity, cloudiness, and atmospheric pressure) instead of daily values. The evaluation in this paper covers the period from 1980 to 2009. Only the summer beaching period (May–September) was analysed. The initial data was taken from the European Climate Assessment & Dataset project database. The monthly reanalysis fields of meteorological variables were used for covering the Baltic Sea coasts and adjacent territories (180 grid points). The UTCI values were obtained using BioKlima version 2.6 software. The UTCI values were visualized using ArcGIS 10.2 version software. The evaluation period was divided into two parts (1980–1994 and 1995–2009). The results showed that the temporal and spatial changes are already happening on the coastline. The UTCI values became higher in almost the entire perimeter of the Baltic Sea coastline and the warming process included every summer month. The whole Baltic Sea coastline corresponds to comfortable conditions (UTCI >9°C) of the UTCI categorization from May to August. Only in September did conditions become less comfortable. However, the real "thermal comfort zone" conditions (UTCI >17.5°C) on the Baltic Sea coasts last from the middle of June until the middle of August. The southern part is significantly warmer compared to other parts in May and September, while the UTCI values are more similar over the other summer months. [ABSTRACT FROM AUTHOR]

In coastal catchments, rainfall events primarily drive bacterial inputs to the sea by causing land runoff, surface leaching and sewer overflow. Under semi-arid climate, extensive dry periods are interspersed with extreme precipitation. This paper aims to assess the impact of intense summer rainstorms events on Fecal Indicator Bacteria loadings to Mediterranean seawaters. Firstly, explanatory relationships were derived between an Antecedent Precipitation Index and the loads of thermo-tolerant coliforms and intestinal enterococci measured at three catchment outlets in the Gulf of Aigues-Mortes (southern France). Secondly, fecal bacterial loadings were simulated during summer season from 2006–2016, with a confidence interval arising from measurements uncertainties. On average, more than two rainstorms per summer season elevate bacterial loads at least by one order of magnitude, potentially leading to the degradation of bathing and fishing water quality observed in regulatory monitoring data. The results highlight the crucial importance of considering hydrological conditions in coastal water quality management. [ABSTRACT FROM AUTHOR]

This paper analyses current precipitation rates (PRs) and trends over the Mediterranean Sea region and their response to global climate change scenarios. The analysis uses 0.25° gridded PRs dataset over a 13-year period (1998-2010) based on remote sensing data from the Tropical Rainfall Measuring Mission. Future scenarios use the results of six global climate models (GCMs) under four representative concentration pathway scenarios (i.e., RCP26, RCP45, RCP60, and RCP85). Results indicate that the Mediterranean Sea region displays a seasonally significant (insignificant) wetter trend during cold (hot) seasons, and exhibits annual spatial variation ranging from under 15 to over 100 mm month -1 over the period 1998-2010. Sea level pressure has two different effects on precipitation over the northern (inversely related to precipitation) versus southern (directly related to precipitation) Mediterranean Sea. However, sea surface temperature is anti-correlated with precipitation. The GCMs that describe the current Mediterranean Sea precipitation most realistically are GFDL-CM3-1, MIROC-ESM-CHEM, and HadGEM2-AO, which are used to calculate the ensemble mean for each representative concentration pathway scenario. The ensemble means realizations indicate that the study area will experience substantial drought in the 21st century. Uncertainty in the projected precipitation over the Mediterranean Sea was partitioned into four sources, of which the used scenario dominates. [ABSTRACT FROM AUTHOR]

Abstract: The Arctic Oscillation (AO) has been found in previous studies to be a major synoptic factor affecting the climate of many regions in the high and mid-latitudes. This paper demonstrates the physical process by which the AO affects the climate of the Eastern Mediterranean basin, with a focus on precipitation in Israel as a case study. It is shown that a trend of increasing AO is associated with a substantial decrease of winter precipitation from the Iberian Peninsula, though Italy, Greece, Turkey and Cyprus, as well as Lebanon, Syria and also the northern parts of Israel. Winter rain is slightly increased in the southern coast of the eastern half of the Mediterranean Sea. The immediate meteorological causes are shown to be a larger northerly component of the flow over the Mediterranean Sea, associated with a decreasing relative humidity and stability, except over the southern coast, where the air mass has the longest track over the relatively warm water. We suggest here that the observed changes in air flow that drives the precipitation trends can be explained by shifts in the AO that can be partially explained by increasing greenhouses gases. Results from the IPCC multi climate models show that the AO will continue to increase during the 21st century. This increase may lead to a continuation of the trends discussed here. The importance of the analysis provided here is in pointing out the possibility that processes that have been predicted by global warming and changes in global circulation have already started to affect precipitation and major water resources in the Mediterranean basin. [Copyright &y& Elsevier]

Within the CIRCE project 'Climate change and Impact Research: the Mediterranean Environment', an ensemble of high resolution coupled atmosphere-ocean regional climate models (AORCMs) are used to simulate the Mediterranean climate for the period 1950-2050. For the first time, realistic net surface air-sea fluxes are obtained. The sea surface temperature (SST) variability is consistent with the atmospheric forcing above it and oceanic constraints. The surface fluxes respond to external forcing under a warming climate and show an equivalent trend in all models. This study focuses on the present day and on the evolution of the heat and water budget over the Mediterranean Sea under the SRES-A1B scenario. On the contrary to previous studies, the net total heat budget is negative over the present period in all AORCMs and satisfies the heat closure budget controlled by a net positive heat gain at the strait of Gibraltar in the present climate. Under climate change scenario, some models predict a warming of the Mediterranean Sea from the ocean surface (positive net heat flux) in addition to the positive flux at the strait of Gibraltar for the 2021-2050 period. The shortwave and latent flux are increasing and the longwave and sensible fluxes are decreasing compared to the 1961-1990 period due to a reduction of the cloud cover and an increase in greenhouse gases (GHGs) and SSTs over the 2021-2050 period. The AORCMs provide a good estimates of the water budget with a drying of the region during the twenty-first century. For the ensemble mean, he decrease in precipitation and runoff is about 10 and 15% respectively and the increase in evaporation is much weaker, about 2% compared to the 1961-1990 period which confirm results obtained in recent studies. Despite a clear consistency in the trends and results between the models, this study also underlines important differences in the model set-ups, methodology and choices of some physical parameters inducing some difference in the various air-sea fluxes. An evaluation of the uncertainty sources and possible improvement for future generation of AORCMs highlights the importance of the parameterisation of the ocean albedo, rivers and cloud cover. [ABSTRACT FROM AUTHOR]

The land area surrounding the Mediterranean Sea has experienced 10 of the 12 driest winters since 1902 in just the last 20 years. A change in wintertime Mediterranean precipitation toward drier conditions has likely occurred over 1902-2010 whose magnitude cannot be reconciled with internal variability alone. Anthropogenic greenhouse gas and aerosol forcing are key attributable factors for this increased drying, though the external signal explains only half of the drying magnitude. Furthermore, sea surface temperature (SST) forcing during 1902-2010 likely played an important role in the observed Mediterranean drying, and the externally forced drying signal likely also occurs through an SST change signal. The observed wintertime Mediterranean drying over the last century can be understood in a simple framework of the region's sensitivity to a uniform global ocean warming and to modest changes in the ocean's zonal and meridional SST gradients. Climate models subjected to a uniform ++0.5°C warming of the world oceans induce eastern Mediterranean drying but fail to generate the observed widespread Mediterranean drying pattern. For a ++0.5°C SST warming confined to tropical latitudes only, a dry signal spanning the entire Mediterranean region occurs. The simulated Mediterranean drying intensifies further when the Indian Ocean is warmed ++0.5°C more than the remaining tropical oceans, an enhanced drying signal attributable to a distinctive atmospheric circulation response resembling the positive phase of the North Atlantic Oscillation. The extent to which these mechanisms and the region's overall drying since 1902 reflect similar mechanisms operating in association with external radiative forcing are discussed. [ABSTRACT FROM AUTHOR]

Gridded monthly evaporation data for 1958-2006 from the Woods Hole Oceanographic Institution data set are used to investigate interannual variability of Mediterranean evaporation during cold and hot seasons and its relation to regional atmospheric dynamics, sea surface temperature and atmospheric elements of the hydrological cycle. The first EOF mode of Mediterranean evaporation, explaining more than 50% of its total variance, is characterized by the monopole pattern both in winter and summer. However, despite structural similarity, the EOF-1 of Mediterranean evaporation is affected by different climate signals in cold and hot seasons. During winter the EOF-1 is associated with the East Atlantic teleconnection pattern. In summer, there is indication of tropical influence on the EOF-1 of Mediterranean evaporation (presumably from Asian monsoon). Both in winter and summer, principal components of EOF-1 demonstrate clear interdecadal signals (with a stronger signature in summer) associated with large sea surface temperature anomalies. The results of a sensitivity analysis suggest that in winter both the meridional wind and the vertical gradient of saturation specific humidity (GSSH) near the sea surface contribute to the interdecadal evaporation signal. In summer, however, it is likely that the signal is more related to GSSH. Our analysis did not reveal significant links between the Mediterranean evaporation and the North Atlantic Oscillation in any season. The EOF-2 of evaporation accounts for 20% (11%) of its total variance in winter (in summer). Both in winter and summer the EOF-2 is characterized by a zonal dipole with opposite variations of evaporation in western and eastern parts of the Mediterranean Sea. This mode is associated presumably with smaller scale (i.e., local) effects of atmospheric dynamics. Seasonality of the leading modes of the Mediterranean evaporation is also clearly seen in the character of their links to atmospheric elements of the regional hydrological cycle. In particular, significant links to precipitation in some regions have been found in winter, but not in summer. [ABSTRACT FROM AUTHOR]

An observational analysis of Mediterranean Sea water cycle variability based on recently available datasets provides new insights on the long-term changes that affected the region since the 1960s. Results indicate an overall increase in evaporation during 1958–2006, with a decrease up until the mid-1970s and an increase thereafter. Precipitation variability is characterized by substantial interdecadal variations and a negative long-term trend. Evaporation increase, primarily driven by SST variability, together with precipitation decrease resulted in a substantial increase in the loss of freshwater from the Mediterranean Sea toward the overlying atmosphere. An increase in the freshwater deficit is consistent with observed Mediterranean Sea salinity tendencies and has broad implications for the Mediterranean water cycle and connected systems. These observational results are in qualitative agreement with simulated Mediterranean Sea water cycle behavior from a large ensemble of models from the Coupled Model Intercomparison Project Phase 3 (CMIP3). However, simulated anomalies are about one order of magnitude smaller than those observed. This inconsistency and the large uncertainties associated with the observational rates of change highlight the need for more research to better characterize and understand Mediterranean water cycle variations in recent decades, and to better simulate the crucial underlying processes in global models. [ABSTRACT FROM AUTHOR]