The Mediterranean basin has been classified as a hot-spot for climate change. The Mediterranean Sea plays a fundamental regulatory role in the regional climate. We have analyzed the largest available and complete time series (1982–2019) of blended sea surface temperature (SST) data to study its seasonal cycle and look for a possible warming trend in the basin. From the analysis of the Mediterranean mean SST time series, a new temporal seasonal division is derived that differs from the one used in atmospheric climatology. Then, the SST time series were decomposed into their seasonal and trend components, and a consistent warming trend of 0.035 °C/year was obtained. The nature of this trend has been investigated, indicating a higher warming trend for both maximum and high/summer SST values than for the winter/colder ones. This reinforces the consistency of the SST increase since it is not only based on the presence of extreme values, but on a homogeneous basin global increase of high SST records as well. Although warming is found throughout the Mediterranean basin, the spatial variability found leads to the division of the basin into three distinct subareas regarding warming.

Oceans play a key role in energy storage in the global Earth–Ocean–Atmosphere system. Within this framework, the knowledge of past evolution and future trends of sea surface temperature is crucial for the future climate scenarios. Previous studies have highlighted the role of sea surface temperature as an important ingredient for the development and/or intensification of heavy precipitation events in the Western Mediterranean basin but have also highlighted its role in heat waves in Europe. In this study, a consistent warming trend has been found for daily sea surface temperature data series derived from satellites (1982–2016) for the whole Mediterranean region and for different temporal scales, from daily to monthly, seasonal and decadal estimates. Additionally, spatial clustering analysis has been run to look for its spatial structure. Two main distribution modes have been found for sea surface temperature in winter and summer, while spring and fall show transitional regimes. Winter mode shows a north-to-south increasing gradient banded structure while summer regime presents a set of well-differentiated areas.

Mesometeorological information obtained in several research projects in southern Europe has been used to analyze perceived changes in the western Mediterranean summer storm regime. A procedure was developed to disaggregate daily precipitation data into three main components: frontal precipitation, summer storms, and Mediterranean cyclogenesis. Working hypotheses were derived on the likely processes involved. The results indicate that the precipitation regime in this Mediterranean region is very sensitive to variations in surface airmass temperature and moisture. Land-use perturbations that accumulated over historical time and greatly accelerated in the last 30 yr may have induced changes from an open, monsoon-type regime with frequent summer storms over the mountains inland to one dominated by closed vertical recirculations where feedback mechanisms favor the loss of storms over the coastal mountains and additional heating of the sea surface temperature during summer. This, in turn, favors Mediterranean cyclogenesis and torrential rains in autumn–winter. Because these intense rains and floods can occur anywhere in the basin, perturbations to the hydrological cycle in any part of the basin can propagate to the whole basin and adjacent regions. Furthermore, present levels of air pollutants can produce greenhouse heating, amplifying the perturbations and pushing the system over critical threshold levels. The questions raised are relevant for the new European Union (EU) water policies in southern Europe and for other regions dominated by monsoon-type weather systems.

Marine heat waves (MHW), considered as persistent and spatially extensive sea surface temperature (SST) anomalies, have emerged as one of the global change-induced high impact events on the oceans. The study of MHWs received significant progress in recent years, although many unknowns remain. One of the most notable weaknesses is related to the absence of a universally established definition that would allow better intercomparison of results. It is our aim to contribute to this debate by considering the spatial extent to define a MHW. By applying this hypothesis to a relatively small, but complex, basin such as the Mediterranean, MHWs have been characterized and long-term trends assessed from SST satellite data analysis. Our results show that the inclusion of a minimum area threshold, 5 % of the area basin, greatly reduces the population of MHW events by not considering local SST anomalies that do not constitute a MHW event. A trend to more frequent, intense, and longer MHWs is found in the 1982-2021 period in the Mediterranean. In the spatial characterization and long-term trend analysis, regional differences were apparent. Results evidenced variations in MHWs characteristics and trends across the different sub-basins evidencing the fact that, even in a relatively small basin such as the Mediterranean, significant regional differences make it necessary to include a spatial perspective in the studies, beyond purely local analysis at each observation point in a large basin or even in the global ocean. Regarding the characterization of MHWs and trend analysis in the Mediterranean basin, a growing trend has been found in terms of frequency, duration, and intensity that accelerated since 2000 and especially in the last decade, pointing not just to a steady intensification and higher frequency of MHWs but to the emergence of a new set of more intense, long-lasting and spatially extensive MHWs in the recent years.

The number of large fires increased in the 1970s in the Valencia region (eastern Spain), as in most northern Mediterranean countries, owing to the fuel accumulation that affected large areas as a consequence of an intensive land abandonment. The Ayora site (Valencia province) was affected by a large fire in July 1979. We parameterised the fire growth model FARSITE for the 1979 fire conditions using remote sensing-derived fuel cartography. We simulated different fuel scenarios to study the interactions between fuel spatial distribution and fire characteristics (area burned, rate of spread and fireline intensity). We then tested the effectiveness of several firebreak networks on fire spread control. Simulations showed that fire propagation and behaviour were greatly influenced by fuel spatial distribution. The fragmentation of large dense shrubland areas through the introduction of wooded patches strongly reduced fire size, generally slowing fire and limiting fireline intensity. Both the introduction of forest corridors connecting woodlands and the promotion of complex shapes for wooded patches decreased the area burned. Firebreak networks were always very effective in reducing fire size and their effect was enhanced in appropriate fuel-altered scenarios. Most firebreak alternatives, however, did not reduce either rate of fire spread or fireline intensity.

Torrential rains are a frequent meteorological risk in the Mediterranean Basin, and the work reported here is part of a long-term study that includes the analysis of the synoptic conditions involved in their genesis. This paper studies the role of SST in torrential rain development. Two episodes were selected for simulation with the Regional Atmospheric Modeling System. Three runs of each were performed by progressively improving the SST input data sources: from monthly climatological averages, to data from the International Satellite Land Surface Climatology Project, to near-to-real-time data derived from National Oceanic and Atmospheric Administration (NOAA) satellite images. For the first episode, the maximum total precipitations calculated were 242, 301, and 496 mm, respectively, versus more than 550 mm measured. For the second event, the maxima were 316, 349, and 378 mm, respectively, versus more than 450 mm measured. The conclusion is that significant improvements in the modeling of peak pr... Abstract Torrential rains are a frequent meteorological risk in the Mediterranean Basin, and the work reported here is part of a long-term study that includes the analysis of the synoptic conditions involved in their genesis. This paper studies the role of SST in torrential rain development. Two episodes were selected for simulation with the Regional Atmospheric Modeling System. Three runs of each were performed by progressively improving the SST input data sources: from monthly climatological averages, to data from the International Satellite Land Surface Climatology Project, to near-to-real-time data derived from National Oceanic and Atmospheric Administration (NOAA) satellite images. For the first episode, the maximum total precipitations calculated were 242, 301, and 496 mm, respectively, versus more than 550 mm measured. For the second event, the maxima were 316, 349, and 378 mm, respectively, versus more than 450 mm measured. The conclusion is that significant improvements in the modeling of peak pr...