Trends in warm days and cold nights over the Iberian Peninsula: relationships to large-scale variables

This work analyzes the effects of high temperature days on large wildland fires during 1978–2010 in Aragón (NE Spain). A high temperature day was established when air temperature was higher than 20 °C at 850 hPa. Temperature at 850 hPa was chosen because it properly characterizes the low troposphere state, and some of the problems that affect surface reanalysis do not occur. High temperature days were analyzed from April to October in the study period, and the number of these extreme days increased significantly. This temporal trend implied more frequent adverse weather conditions in later years that could facilitate extreme fire behavior. The effects of those high temperatures days in large wildland fire patterns have been increasingly important in the last years of the series

Section: Discussionsupporting

confidence: 77%

Trends in adverse weather patterns and large wildland fires in Aragón (NE Spain) from 1978 to 2010

Cardíl

Molina

Ramírez

et al. 2013

“…The reported influence of circulation patterns varies across the Mediterranean Basin. Over the Iberian Peninsula, cold extremes have been found to be associated with the East Atlantic (EA) pattern, whereas warm extremes have been associated with the Scandinavia (SCAND) teleconnection pattern (Rodríguez-Puebla et al, 2010). In the Western Mediterranean, blocking conditions favour high summer temperatures (Xoplaki et al, 2003b).…”

Section: Temperature and Atmospheric Circulation Data And Indicesmentioning

confidence: 99%

“…Moreover, the changes are not always steady or monotonic. Thus, other studies have focused on particular subregions of the Mediterranean such as Spain (Brunet et al, 2007;Rodríguez-Puebla et al, 2010), Italy (Baldi et al, 2006;Bartolini et al, 2008;Toreti and Desiato, 2008), Eastern Mediterranean (Founda et al, 2004;Kostopoulou and Jones, 2005;Kuglitsch et al, 2010), and the Levant and northern parts of Egypt and Libya (Domroes and El-Tantawi, 2005;Zhang et al, 2005;Sensoy et al, 2007;El Kenawy et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Trends in Mediterranean gridded temperature extremes and large-scale circulation influences

Efthymiadis

Goodess

Jones

2011

110

Abstract. Two recently-available daily gridded datasets are used to investigate trends in Mediterranean temperature extremes since the mid-20th century. The underlying trends are found to be generally consistent with global trends of temperature and their extremes: cold extremes decrease and warm/hot extremes increase. This consistency is better manifested in the western part of the Mediterranean where changes are most pronounced since the mid-1970s. In the eastern part, a cooling is observed, with a near reversal in the last two decades. This inter-basin discrepancy is clearer in winter, while in summer changes are more uniform and the west-east difference is restricted to the rate of increase of warm/hot extremes, which is higher in central and eastern parts of the Mediterranean over recent decades. Linear regression and correlation analysis reveals some influence of major large-scale atmospheric circulation patterns on the occurrence of these extremes -both in terms of trend and interannual variability. These relationships are not, however, able to account for the most striking features of the observations -in particular the intensification of the increasing trend in warm/hot extremes, which is most evident over the last 15-20 yr in the Central and Eastern Mediterranean.

“…In particular, the relationship between temperature extremes in Europe and large-scale circulation patterns has been widely studied (Yiou and Nogaj, 2004;Cassou et al, 2005;Santos and Corte-Real, 2006;Della-Marta et al, 2007;Jacobeit et al, 2009;Rodriguez-Puebla et al, 2010;Andrade et al, 2012). These studies highlighted the important role of the North Atlantic Oscillation (NAO) for temperature extremes in winter.…”

Section: Introductionmentioning

confidence: 99%

Characterising the relationship between weather extremes in Europe and synoptic circulation features

Pfahl

2014

138

132

Abstract. Extreme weather events in Europe are closely linked to anomalies of the atmospheric circulation and in particular to circulation features like cyclones and atmospheric blocking. In this study, this linkage is systematically characterised with the help of conditional cyclone and blocking frequencies during precipitation, wind gust and temperature extremes at various locations in Europe. Such conditional frequency fields can serve as a dynamical fingerprint of the extreme events and yield insights into their most important physical driving mechanisms. Precipitation extremes over the ocean and over flat terrain are shown to be closely related to cyclones in the vicinity and the associated dynamical lifting. For extreme precipitation over complex terrain, cyclone anomalies are found at more remote locations, favouring the flow of moist air towards the topography. Wind gust extremes are associated with cyclone and blocking anomalies in opposite directions, with the cyclones occurring mostly over the North and Baltic seas for extreme events in central Europe. This setting is associated with pronounced surface pressure gradients and thus high near-surface wind velocities. Hot temperature extremes in northern and central Europe typically occur in the vicinity of a blocking anticyclone, where subsidence and radiative forcing are strong. Over southern Europe, blocking anomalies are shifted more to the north or northeast, indicating a more important role of warm air advection. Large-scale flow conditions for cold extremes are similar at many locations in Europe, with blocking anomalies over the North Atlantic and northern Europe and cyclone anomalies southeast of the cold extreme, both contributing to the advection of cold air masses. This characterisation of synoptic-scale forcing mechanisms can be helpful for better understanding and anticipating weather extremes and their long-term changes.