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

Anuncios

9TH HYMEX WORKSHOP, 21-25 SEPTEMBER 2015, MYKONOS, GREECE

General information

The 9th HyMeX workshop will take place from 21 to 25 September 2015, in Mykonos Island, Greece. It will be organized by the National Observatory of Athens at Saint-John hotel.

Objectives

The general objectives of all the HyMeX workshops are to strengthen the links and knowledge exchange, as well as to foster collaborations within the HyMeX community. The 9th HyMeX workshop will occur at mid-term of the programme. It will be the opportunity to assess the achievements of the programme, both in terms of data collected and scientific studies, against the original objectives of the Science Plan. Running over 5 days, the programme will consist of plenary sessions with review solicited talks and Science Teams oral and poster sessions with an open call for contributions to present and discuss recent scientific progresses in the understanding of the Mediterranean water cycle, from multiscale and multidisciplinary approaches. Leer más de esta entrada

The role of different factors related to social impact of heavy rain events: considerations about the intensity thresholds in densely populated areas

ABSTRACT: 

In the assessment of social impact caused by meteorological events, factors of different nature need to be considered. Not only does hazard itself determine the impact that a severe weather event has on society, but also other features related to vulnerability and exposure.

The requests of data related to insurance claims received in Meteorological Services proved to be a good indicator of the social impact that a weather event causes, according to studies carried out by the Social Impact Research Group, created under the frame of the MEDEX project. Taking these requests as proxy data, diverse aspects connected to the impact of heavy rain events have been studied.

The rainfall intensity in conjunction with the population density has demonstrated to be one of the key factors in social impact studies. One of the conclusions we obtained is that various thresholds of rainfall should be applied for differently populated areas. In this study, the role of rainfall intensity has been analysed for a highly populated urban area like Barcelona. A period without significant population changes has been selected for the study to minimise the effects linked to vulnerability and exposure. First, correlations between rainfall recorded in different time intervals and requests have been carried out. Afterwards, a method to include the intensity factor in the social impact index has been suggested, based on return periods given by Intensity-Duration-Frequency (IDF) curves.

Authors: L. Barbería, J. Amaro, M. Aran, and M. C. Llasat

LINK: www.nat-hazards-earth-syst-sci-discuss.net/2/459/2014/nhessd-2-459-2014.html

Flash flood evolution in North-Western Mediterranean

Abstract

The present paper shows an in-depth analysis of the evolution of floods and precipitation in Catalonia for the period 1981–2010. In order to have homogeneous information, and having in mind that not gauge data was available for all the events, neither for all the rivers and stream flows, daily press from a specific newspaper has been systematically analysed for this period. Furthermore a comparison with a longer period starting in 1900 has been done. 219 flood events (mainly flash flood events) have been identified for the period of 30 years (375 starting in 1900), 79 of them were ordinary, 117 of them were extraordinary and 23 of them were catastrophic, being autumn and summer the seasons with the maxima values. 19% of the events caused a total of 110 casualties. 60% of them died when they tried to cross the street or the stream. Factors like the evolution of precipitation, population density and other socio-economical aspects have been considered. The trend analysis shows an increase of 1 flood/decade that probably has been mainly due to inter-annual and intra-annual changes in population density and in land-use and land-cover.

Authors: Maria Carmen Llasat, Raül Marcos, Montserrat Llasat-Botijaa, Joan Gilabert, Marco Turco i Pere Quintana-Seguí.

Podéis descargar el artículo de forma gratuita hasta el 31 de agosto. LINK:  http://authors.elsevier.com/a/1PLdgcd3RmlUW

Climate change impacts on wildfires in a Mediterranean environment

Nou artícle publicat a Climatic Change sobre els impactes del canvi climàtic als incencis del Mediterrani.

 

Abstract

We analyse the observed climate-driven changes in summer wildfires and their future evolution in a typical Mediterranean environment (NE Spain). By analysing observed climate and fire data from 1970 to 2007, we estimate the response of fire number (NF) and burned area (BA) to climate trends, disentangling the drivers responsible for long-term and interannual changes by means of a parsimonious Multi Linear Regression model (MLR). In the last forty years, the observed NF trend was negative. Here we show that, if improvements in fire management were not taken into account, the warming climate forcing alone would have led to a positive trend in NF. On the other hand, for BA, higher fuel flammability is counterbalanced by the indirect climate effects on fuel structure (i.e. less favourable conditions for fine-fuel availability and fuel connectivity), leading to a slightly negative trend. Driving the fire model with A1B climate change scenarios based on a set of Regional Climate Models from the ENSEMBLES project indicates that increasing temperatures promote a positive trend in NF if no further improvements in fire management are introduced.

AUTHORS: Marco Turco, María del Carmen Llasat, Jost von Hardenberg and Antonello Provenzale.

Podeu descarregar-lo clicant AQUÍ.

The snow storm of 8 March 2010 in Catalonia (Spain): a paradigmatic wet-snow event with a high societal impact

Authors.  M. C. Llasat, M. Turco, P. Quintana-Seguí and M. Llasat-Botija

Abstract. 

A heavy precipitation event swept over Catalonia (NE Spain) on 8 March 2010, with a total amount that exceeded 100 mm locally and snowfall of more than 60 cm near the coast. Unusual for this region and at this time of the year, this snowfall event affected mainly the coastal region and was accompanied by thunderstorms and strong wind gusts in some areas. Most of the damage was due to “wet snow”, a kind of snow that favours accretion on power lines and causes line-breaking and subsequent interruption of the electricity supply. This paper conducts an interdisciplinary analysis of the event to show its great societal impact and the role played by the recently developed social networks (it has been called the first “Snowfall 2.0”), as well to analyse the meteorological factors associated with the major damage, and to propose an indicator that could summarise them. With this aim, the paper introduces the event and its societal impact and compares it with other important snowfalls that have affected the Catalan coast, using the PRESSGAMA database. The second part of the paper shows the event’s main meteorological features and analyses the near-surface atmospheric variables responsible for the major damage through the application of the SAFRAN (Système d’analyse fournissant des renseignements atmosphériques à la neige) mesoscale analysis, which, together with the proposed “wind, wet-snow index” (WWSI), allows to estimate the severity of the event. This snow storm provides further evidence of our vulnerability to natural hazards and highlights the importance of a multidisciplinary approach in analysing societal impact and the meteorological factors responsible for this kind of event.

Full article HERE.

 

HyMeX, a 10-year multidisciplinary program on the Mediterranean water cycle

Authors:

P. Drobinski, V. Ducrocq, P. Alpert, E. Anagnostou, K. Béranger, M. Borga, I. Braud, A.Chanzy, S. Davolio, G. Delrieu, C. Estournel, N. Filali Boubrahmi, J. Font, V. Grubisic, S. Gualdi, V. Homar, B. Ivancan- Picek, C. Kottmeier, V. Kotroni, K. Lagouvardos, P. Lionello, M.C. Llasat, W. Ludwig,  C. Lutoff, A. Mariotti, E. Richard, R. Romero, R. Rotunno, O. Roussot, I. Ruin, S. Somot, I. Taupier-Letage, J. Tintore, R.Uijlenhoet, H. Wernli

Abstract:

The Mediterranean countries are experiencing important challenges related to the water cycle including water shortages and floods, extreme winds and ice/snow storms that impact critically the socioeconomic vitality in the area (causing damage to property; threatening lives; affecting the energy and transportation sectors, etc.). There are gaps in our understanding of the Mediterranean water cycle and its dynamics, which include the variability of the Mediterranean Sea water budget and its feedback on the variability of the continental precipitation through air/sea interactions, the impact of precipitation variability on aquifer recharge, river discharge, soil water content and vegetation characteristics specific of the Mediterranean basin and the mechanisms that control the location and intensity of heavy precipitating systems which often produce floods. The HyMeX (Hydrological cycle in the Mediterranean Experiment) programme is a 10-year concerted experimental effort at the international level aiming at advancing the scientific knowledge of the water cycle variability in all compartments (land, sea and atmosphere) and at various time and spatial scales. It also aims at improving the processes-based models needed for forecasting hydro-meteorological extremes and the models of the regional climate system for predicting regional climate variability and evolution. It finally aims at assessing the social and economic vulnerability to hydrometeorological natural hazards in the Mediterranean and the adaptation capacity of the territories and populations therein to provide support to policy makers to cope with water related problems under the influence of climate change, by linking scientific outcomes with related policy requirements. Leer más de esta entrada