EL BLOG DE GAMA

GAMA (Grupo de Análisis de situaciones Meteorológicas Adversas) es un grupo de investigación interdisciplinario del Departament d’Astronomia i meteorología de la Universitat de Barcelona. Sus principales lineas de investigación son: el estudio de fenómenos meteorológicos adversos y riesgos naturales (episodios de precipitaciones extremas, inundaciones, riadas, tormentas, sequías, incendios forestales,…); Cambio climático (análisis de series meteorológicas, tendencias y anomalías, impacto del cambio climático en los riesgos naturales); Previsión hidrometeorológica (nowcasting, estacional); Análisis del impacto social, percepción y comunicación social de los riesgos naturales.

Con el fin de poder difundir información relacionada con las líneas de estudio, nos hemos propuesto empezar un blog con el título de Riesgos Naturales, un espacio de divulgación meteorológica, así como de comunicación y sensibilización frente a los riesgos naturales y el cambio climático.

3 nous artícles

On the key role of droughts in the dynamics of summer fires in Mediterranean Europe

 

Marco Turco, Jost von Hardenberg, Amir AghaKouchak, Maria Carmen Llasat, Antonello Provenzale, Ricardo M. Trigo

 

Summer fires frequently rage across Mediterranean Europe, often intensified by high temperatures and droughts. According to the state-of-the-art regional fire risk projections, in forthcoming decades climate effects are expected to become stronger and possibly overcome fire prevention efforts. However, significant uncertainties exist and the direct effect of climate change in regulating fuel moisture (e.g. warmer conditions increasing fuel dryness) could be counterbalanced by the indirect effects on fuel structure (e.g. warmer conditions limiting fuel amount), affecting the transition between climate-driven and fuel-limited fire regimes as temperatures increase. Here we analyse and model the impact of coincident drought and antecedent wet conditions (proxy for the climatic factor influencing total fuel and fine fuel structure) on the summer Burned Area (BA) across all eco-regions in Mediterranean Europe. This approach allows BA to be linked to the key drivers of fire in the region. We show a statistically significant relationship between fire and same-summer droughts in most regions, while antecedent climate conditions play a relatively minor role, except in few specific eco-regions. The presented models for individual eco-regions provide insights on the impacts of climate variability on BA, and appear to be promising for developing a seasonal forecast system supporting fire management strategies.

Article: http://www.nature.com/articles/s41598-017-00116-9

Analysis of geographic and orographic influence in Spanish monthly precipitation

J. Álvarez-Rodríguez, M. C. Llasat, T. Estrela

Precipitation is a major concern in water resources studies. Being a main variable, the inefficiency of historical ground network, particularly at higher altitudes where precipitation and runoff augmentations are expected, constitutes a major drawback. This work analyses the competence of Spanish historical precipitation network and explores the physiographic influence of elevation and orientation at a national scale. The usefulness of slopes is also explored. Nearly 12 000 monthly precipitation series recorded from the 19th century until the hydrological year 2004/2005 over a high-resolution topographic map (200 m) of Spanish territory are used. Comparable statistics and precipitation lapse rates are managed once a completion of gaps is accomplished. Then, Spanish yearly rates range from 0.3 to 1.2 mm m−1, reaching 1.5 mm m−1 in Northern Iberian Peninsula, diminishing at highest altitudes.

Article: http://onlinelibrary.wiley.com/doi/10.1002/joc.5007/full

Bias correction and downscaling of future RCM precipitation projections using a MOS-Analog technique

M. Turco, M.C. Llasat, S. Herrera, J.M Gutiérrez

In this study we assess the suitability of a recently introduced analog-based Model Output Statistics (MOS) downscaling method (referred to as MOS-Analog) for climate change studies and compare the results with a quantile mapping bias correction method. To this aim, we focus on Spain and consider daily precipitation output from an ensemble of Regional Climate Models provided by the ENSEMBLES project. The reanalysis-driven Regional Climate Model (RCM) data provide the historical data (with day-to-day correspondence with observations induced by the forcing boundary conditions) to conduct the analog search of the control (20C3M) and future (A1B) global climate model (GCM)-driven RCM values. First, we show that the MOS-Analog method outperforms the raw RCM output in the control 20C3M scenario (period 1971–2000) for all considered regions and precipitation indices, although for the worst-performing models the method is less effective. Second, we show that the MOS-Analog method broadly preserves the original RCM climate change signal for different future periods (2011–2040, 2041–2070, 2071–2100), except for those indices related to extreme precipitation. This could be explained by the limitation of the analog method to extrapolate unobserved precipitation records. These results suggest that the MOS-Analog is a spatially consistent alternative to standard bias correction methods, although the limitation for extreme values should be taken with caution in cases where this aspect is relevant for the problem.

Article: http://onlinelibrary.wiley.com/doi/10.1002/2016JD025724/abstract

10th HyMeX Workshop, 4-7 July 2017, Barcelona, Spain

Barcelona, Spain

The 10th HyMeX workshop will take place from 4 to 7 July 2017, in Barcelona, Spain.
It will be organized by the Water Research Institute (IdRA) and the Faculty of Physics from the University of Barcelona.

  • 2d circular in pdf format
  • Short abstracts for oral or poster presentations are invited related to the Mediterranean water cycle.
    Themes of particular interest are: heavy precipitation, flash-flood and vulnerabilities, Mediterranean cyclones, ocean circulation and dense water formation, droughts and water resources. Contributions on recent advances in prediction and management of the water cycle, its link with renewable energy, its related hazards and their impacts, from nowcasting to climate scales, are also welcome.
    Short abstracts can be submitted online here (Submission deadline is extended to 17 March 2017)
  • Registration form
Scientific committee
    M.C. Llasat (Chair, U. Barcelona, Es), V. Ducrocq (Co-chair, CNRM, Fr), P. Alpert (TAU, Is), M. Borga (U. Padova, It), I. Braud (IRSTEA, Fr), S. Coquillat (LA, Fr), Ph. Drobinski (LMD-IPSL, Fr), C. Estournel (LA, Fr), E. Flaounas (NOA, Gr), N. Fourrie (CNRM, Fr), V. Homar (UIB, Es), S. Khodayar (KIT, De), V. Kotroni (NOA, Gr), P. Quintana (O. Ebre, Es), S. Somot (CNRM, Fr), A. Turiel (ICM, Es)
Organizing committee
    M.C. Llasat, J. Martin-Vide, J. Bech, N. Casals, P. Guitchev (IdRA, U. Barcelona), M. Llasat-Botija, A. del Moral, M. Cortes, J. Gilabert, (U. Barcelona), P. Quintana (O. Ebre), L. Labatut, O. Roussot (CNRM, Fr)

ACCOMMODATION:

Inundacions 1-3 novembre 2015

Fa un any, entre els dies 1 i 3 de novembre va tenir lloc un fort temporal que va produir nombroses inundacions en el territori. A Catalunya, les comarques més afectades van ser: Segrià, La Segarra, Barcelonès, Tarragonès, Baix Llobregat, Ribera d’Ebre, Baix Ebre, Urgell, Vallès Occidental, Baix Camp, Alt Penedès, Conca de Barberà.

Les quantitats de precipitació acumulada van ser superiors als 100 mm en molt punts, destacant els 220,7 mm del Parc Nacional dels Ports o els 189,9 mm del municipi de Viladrau entre els 3 dies que va durar l’episodi. Alguns rius es van desbordar provocant greus inundacions sobretot de baixos i soterranis. A Agramunt, la matinada del 3/11, es van produir 4 víctimes mortals degut al desbordament del riu Sió.

El pase de diapositivas requiere JavaScript.

(Fotos de A. Cangròs, J.J. Raventós, O. Rodríguez, compartides amb l’App FLOODUP).

El temporal de llevant va provocar altres conseqüències com un fort temporal de mar que va produir afectacions a les platges de gran part del Mediterrani espanyol, com a les de les províncies d’Alacant o Màlaga, produint inundacions de carrers i locals prop de la franja marítima i destrosses en alguns passeigs marítims. Al municipi de Mont-Roig del Camp es va produir un tornado que va malmetre teulades, arbres i faroles.

 

Ofertes de postdoc

POSTDOC 1:

cnrm

POSTDOC 2:

med-climate-modelling

More information in: HYMEX

13 COLLOQUE GÉORISQUE

colloque-georisque

Trends in flash flood events versus convective precipitation in the Mediterranean region: The case of Catalonia

Maria Carmen Llasat, Raul Marcos, Marco Turco, Joan Gilabert, Montserrat Llasat-Botija

ABSTRACT

The aim of this paper is to analyse the potential relationship between flash flood events and convective precipitation in Catalonia, as well as any related trends. The paper starts with an overview of flash floods and their trends in the Mediterranean region, along with their associated factors, followed by the definition of, identification of, and trends in convective precipitation. After this introduction the paper focuses on the north-eastern Iberian Peninsula, for which there is a long-term precipitation series (since 1928) of 1-min precipitation from the Fabra Observatory, as well as a shorter (1996–2011) but more extensive precipitation series (43 rain gauges) of 5-min precipitation. Both series have been used to characterise the degree of convective contribution to rainfall, introducing the β parameter as the ratio between convective precipitation versus total precipitation in any period. Information about flood events was obtained from the INUNGAMA database (a flood database created by the GAMA team), with the aim of finding any potential links to convective precipitation. These flood data were gathered using information on damage where flood is treated as a multifactorial risk, and where any trend or anomaly might have been caused by one or more factors affecting hazard, vulnerability or exposure. Trend analysis has shown an increase in flash flood events. The fact that no trends were detected in terms of extreme values of precipitation on a daily scale, nor on the associated ETCCDI (Expert Team on Climate Change Detection and Indices) extreme index, could point to an increase in vulnerability, an increase in exposure, or changes in land use. However, the summer increase in convective precipitation was concentrated in less torrential events, which could partially explain this positive trend in flash flood events. The β parameter has been also used to characterise the type of flood event according to the features of the precipitation. The highest values correspond to short and local events, usually with daily β values above 0.5, while the minimum threshold of daily β for catastrophic flash floods is 0.31

Keywords

  • Flash floods;
  • Convective precipitation;
  • β parameter;
  • Trend analysis;
  • Mediterranean

You can download here: http://www.sciencedirect.com/science/article/pii/S0022169416303079

Regional differential behaviour of maximum temperatures in the Iberian Peninsula regarding the Summer NAO in the second half of the twentieth century

V. Favà, J.J. CurtoM.C. Llasat

Abstract

The relationship between atmospheric circulation in northern Europe in summer and the maximum temperatures (Tx) of the Iberian Peninsula (IP) have received little attention. In this article we explore which synoptic structures related to high absolute values of SNAO (Summer North Atlantic Oscillation) are linked to significant anomalies in the maximum temperatures of the IP on a regional scale. Furthermore, we examine how the frequency of these structures has contributed to the differential evolution of maximum temperature trends in the IP and modulated the relationship between the SNAO and the maximum temperatures of the IP in the second half of the twentieth century.

Four basic synoptic structures were identified and their time series were calculated. Thus, we can explain why significant positive correlations between the SNAO and the maximum temperatures for the north of the IP are found for the 1951–1967 period, while in the 1962–1978 period these correlations are negative and affect the eastern part of the IP.

We found that, for the 1951–1967 period, the negative SNAO contributed to a lowering of the maximum temperatures in the NW and north IP and to a strengthening of the north-south IP maximum temperature gradient. During the 1970s and the start of the 1980s, owing to the much higher values of SNAO, the more negative anomalies in the coldest days shifted towards the east of the IP.

Keywords

  • Summer NAO;
  • Maximum temperatures;
  • Regional trends;
  • Temperature gradient;
  • Pressure gradient;
  • Iberian Peninsula

You can download here: http://www.sciencedirect.com/science/article/pii/S0169809516302319