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Trapero L.,Institute dEstudis Andorrans CENMA IEA | Bech J.,University of Barcelona | Lorente J.,University of Barcelona
Atmospheric Research | Year: 2013

This study examines the effect of the orography on two heavy precipitation events (HPE1 and HPE2) which exceeded 100mm in 24h and affected the Eastern Pyrenees (Andorra, NE Spain and SE France) in the NW Mediterranean. High resolution simulations (3km) performed with the Weather and Research Forecasting model (WRF) were compared with precipitation observations to assess the ability of the model to reproduce the spatial distribution of the rainfall field in this mountainous area and determine the prominent factors of intense precipitation occurrence. The analysis has been focused on the association of the heavy rainfall to the existing atmospheric disturbance and the presence of orographic induced vertical motions. For both episodes at 3km resolution, on exposed mountain sides, vertical moisture fluxes characterized with the orographic moisture flux index (OMF) yielded values above 7gkg-1ms-1, consistent with previous studies. The spatial distribution of the OMF maximum is in agreement with the observed rainfall maxima over the Eastern Pyrenees according to the combination of two factors, namely the normal orientation of mountain range with respect to the prevailing moisture flows and large wind speeds of the impinging upstream flows (~20m/s). Moreover, the analyses of a triggering term and moist Froude number also reflect the complexity of applying theoretical results obtained in idealized simulations with 2D mountain ridges to numerical simulations with dynamic evolving conditions over areas with complex orography as the Eastern Pyrenees. © 2012 Elsevier B.V. Source

Komac B.,Institute dEstudis Andorrans CENMA IEA | Esteban P.,University of Barcelona | Trapero L.,Institute dEstudis Andorrans CENMA IEA | Caritg R.,Institute dEstudis Andorrans CENMA IEA
PLoS ONE | Year: 2016

Mountain areas are particularly sensitive to climate change. Species distribution models predict important extinctions in these areas whose magnitude will depend on a number of different factors. Here we examine the possible impact of climate change on the Rhododendron ferrugineum (alpenrose) niche in Andorra (Pyrenees). This species currently occupies 14.6 km2 of this country and relies on the protection afforded by snow cover in winter. We used high-resolution climatic data, potential snow accumulation and a combined forecasting method to obtain the realized niche model of this species. Subsequently, we used data from the high-resolution Scampei project climate change projection for the A2, A1B and B1 scenarios to model its future realized niche model. The modelization performed well when predicting the species's distribution, which improved when we considered the potential snow accumulation, the most important variable influencing its distribution. We thus obtained a potential extent of about 70.7 km2 or 15.1% of the country. We observed an elevation lag distribution between the current and potential distribution of the species, probably due to its slow colonization rate and the small-scale survey of seedlings. Under the three climatic scenarios, the realized niche model of the species will be reduced by 37.9-70.1 km2 by the end of the century and it will become confined to what are today screes and rocky hillside habitats. The particular effects of climate change on seedling establishment, as well as on the species' plasticity and sensitivity in the event of a reduction of the snow cover, could worsen these predictions. © 2016 Komac et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source

Pineda N.,Meteorological Service of Catalonia SMC | Esteban P.,Institute dEstudis Andorrans CENMA IEA | Esteban P.,University of Barcelona | Trapero L.,Institute dEstudis Andorrans CENMA IEA | And 3 more authors.
Physics and Chemistry of the Earth | Year: 2010

In the present study, we use a Principal Component Analysis (PCA) to characterize the surface 6-h circulation types related to substantial lightning activity over the Catalonia area (north-eastern Iberia) and the Principality of Andorra (eastern Pyrenees) from January 2003 to December 2007. The gridded data used for classification of the circulation types is the NCEP Final Analyses of the Global Tropospheric Analyses at 1° resolution over the region 35°N-48°N by 5°W-8°E. Lightning information was collected by the SAFIR lightning detection system operated by the Meteorological Service of Catalonia (SMC), which covers the region studied. We determined nine circulation types on the basis of the S-mode orthogonal rotated Principal Component Analysis. The " extreme scores" principle was used previous to the assignation of all cases, to obtain the number of final types and their centroids. The distinct differences identified in the resulting mean Sea Level Pressure (SLP) fields enabled us to group the types into three main patterns, taking into account their scale/dynamical origin. The first group of types shows the different distribution of the centres of action at synoptic scale associated with the occurrence of lightning. The second group is connected to mesoscale dynamics, mainly induced by the relief of the Pyrenees. The third group shows types with low gradient SLP patterns in which the lightning activity is a consequence of thermal dynamics (coastal and mountain breezes).Apart from reinforcing the consistency of the groups obtained, analysis of the resulting classification improves our understanding of the geographical distribution and genesis factors of thunderstorm activity in the study area, and provides complementary information for supporting weather forecasting. Thus, the catalogue obtained will provide advances in different climatological and meteorological applications, such as nowcasting products or detection of climate change trends. © 2010 Elsevier Ltd. Source

Komac B.,Institute dEstudis Andorrans CENMA IEA | Pladevall C.,Institute dEstudis Andorrans CENMA IEA | Domenech M.,Institute dEstudis Andorrans CENMA IEA | Fanlo R.,University of Lleida
Applied Vegetation Science | Year: 2015

Questions: Humans are altering land use and impacting grazing intensities worldwide in alpine and sub-alpine grasslands, and functional diversity (FD) is a useful tool for predicting changes in these grassland communities and for improving biodiversity conservation. We asked: (1) how does functional richness (FRic) differ between the five predominant grassland types in Andorra (2) of these five grassland types, which plant communities are subject to high habitat filtering and which are driven primarily by competitive interactions; (3) are certain grassland communities more prone to degradation than others; and (4) how do grazing intensity and elevation influence variations in FD indices? Locations: Five types of sub-alpine and alpine grassland communities dominated by Festuca airoides, F. eskia, F. gautieri, F. paniculata and Nardus stricta in Andorra, at various elevations and with differing grazing intensities within a grassland type. Methods: We used multiple functional diversity indices and structural equation modelling (SEM) to determine how grazing intensity, elevation, species richness and productivity affect functional diversity in 222 vegetation transects. Results: Both plant diversity and functional richness were higher at higher grazing intensities, with the highest values found in the F. gautieri and F. paniculata grasslands and lowest in the Nardus stricta, F. airoides and F. eskia grasslands. Habitat filtering was observed in F. airoides grasslands. There was a general tendency for higher competitive interactions among plants at higher elevations and/or when species diversity increased. None of the five grassland communities considered appears disturbed, and all present similar functional attributes between dominant species. Conclusions: Our results highlight the fact that grazing is an integral part of Andorran mountain grasslands, acting as a structural component and providing higher functional richness in the most grazed communities. This paper uses a combination of three different functional diversity indices and structural equation modelling in subalpine and alpine grassland communities in Andorra to understand the effects of grazing intensity on functional diversity and improve biodiversity conservation management. Our results highlight that grazing, a structural component of these mountain grasslands, leads to greater functional richness in the most grazed communities. © 2014 International Association for Vegetation Science. Source

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