Suchergebnisse

The increase in the number of tropical nights (TN; minimum temperature ‡20°C) constitutes important evidence of the global warming process throughout the Mediterranean region. A significant increase in the number of these events has been recorded since the second half of the 20th century. From the meteorological observations in the period 1950-2014 in the regions of Valencia and Murcia, in the central sector of the Spanish Mediterranean coast, we analyse the evolution of the number of tropical nights, the length of the episodes and their frequency. Our results indicate that the study regions experienced a significant increase in tropical nights within the last 3 decades due to climate change and the increase in sea surface temperatures (SST) in the central Western Mediterranean. We also discuss the relationship of the number of tropical nights with the increase in the Mediterranean Sea surface temperatures in the neighbouring sectors, as well as the possible implications of the combined effects of this with the urban heat island effect. Tropical nights are a cause of thermal discomfort, and thus there is a need to adapt buildings and manage urban planning to ameliorate this, and to be prepared for more frequent events in the future. ; R.S.N. was funded by a 'Juan de la Cierva' postdoctoral grant FJCI-2017-31595. J.M. thanks the Spanish Ministerio de Economía y Competitividad and the European Regional Development Fund (FEDER) through the project CGL2015-64268-R (MINECO/FEDER, UE). O.M.R. thanks the Climatology Group (2017SGR1362, Catalan Government) and the CLICES Project (CGL2017-83866-C3-2-R).

Wildfires are gaining importance in the Mediterranean regions owing to climatechange and landscape changes due to the increasing closeness between urban areas and forests prone to wildfires. We analysed the dry season wildfire occurrences in the Mediterranean region of Central Chile (32 degrees S-39 degrees 30'S) between 2000 and 2017, using satellite images to detect burned areas, their landscape metrics and the land use and covers (vegetal) pre-wildfire, in order to determine the population living in areas that may be affected by wildfires. The existing regulations in western Mediterranean countries (Portugal, Spain, France, and Italy) were used to identify and define the wildland-urban interface (WUI) areas, quantifying the people inhabiting them and estimating the population affected by burned areas from 2001 to 2017. We used the Google Earth Engine to process MODIS products and extract both burned areas and land covers. We detected that 25% of the urban population inhabits WUI areas (i.e. Biobio, Araucania and Valparaiso regions) where the urban population exposed to burned areas exceeds 40%. Must of the land use and land covers affected by wildfires are anthropogenic land covers, classified as savannas, croplands, evergreen broadleaf forests and woody savannas, representing >70% of the burned areas. Urban areas show only 0.6% of the burned surface from 2001 to 2017. We estimate that 55,680 people are potentially affected by wildfires, and 50% of them are in just one administrative region. These results show the imperative need for public policies as a regulating force for establishing WU1 areas with the purpose of identifying wildfire risk in urban areas, such as establishing prevention methods as firewalls and prescribed fires. ; Climatology Group (Catalan Government) "Juan de la Cierva" postdoctoral grant CLICES Project Comisión Nacional de Investigación Científica y Tecnológica (CONICYT) CONICYT FONDAP

Northern Chile is a region characterised by an extremely dry climate; however, there is a brief rainy season from December to March (austral summer), mainly above 3000 m a.s.l. It is interesting to consider where the humid air masses that generate such rain come from. For this purpose, daily precipitation data from 161 meteorological stations located in this area (18° S–19° S) were considered, and four clusters formed by k-means clustering. For each cluster, days of extreme precipitation (above 90th percentile) were selected to obtain flow strength (F), direction (D), and vorticity (Z) for each event according to the Jenkinson and Collison (JC) method. The back trajectory, for the previous 72 h, of air masses affecting the centroid of each cluster was determined by means of the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. The analyses were carried out at sea level (1013 hPa) and in the middle (500 hPa) and upper (250 hPa) troposphere. Surface circulation was not a determining factor in the occurrence of extreme events, but it did influence circulation at 500 and 250 hPa. For stations located in the northern Altiplano, moisture advection from the Amazon basin is evident due to the configuration of the Bolivian high—an upper level anticyclone that develops over the Bolivian Altiplano during austral summer. For stations located in the southern part of the study area, the main source of moisture is the Pacific Ocean, and the weather is related to the arrival of frontal systems and to the configuration of cut-off low pressure systems in the mid-troposphere. ; The authors want to thank the FONDECYT Project 11160059 of the Chilean Government, the Climatology Group (2017SGR1362, Catalan Government) and the CLICES Project (CGL2017-83866-C3-2-R) for the institutional support. R.S.N. is funded by the Spanish Ministry of Science and Innovation (grant no. FJCI-2017-31595).