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

Abstract

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.

Spatial and temporal variability of climate extremes in Romania and associated large‐scale mechanisms

“…The same shift was identified in winter ( Figure 3), but in this season the linear trend is more appropriate. This result is in agreement with those presented by Efthymiadis et al (2011) for the Mediterranean temperature extremes. This finding also suggests that for summertime a multidecadal variability of the temperature extremes could be noted, which is in agreement with the conclusion found by Ionita et al (2013) from the analysis of the summer temperature in Romania at 14 stations over a longer period, as well as by Della-Marta et al (2007) for the summer heat waves over western Europe.…”

“…In wintertime, the increasing trend is higher over the extra-Carpathian regions (more pronounced in southern and southeastern regions) and is not significant over some small intra-Carpathian regions. In summer, the trend is significant over the entire country, showing an almost homogeneous magnitude, the results are in agreement with those presented by Efthymiadis et al (2011). A multidecadal variability can be revealed, especially in summertime, when longer time series are examined (e.g.…”

“…For example, Domonkos et al (2003) analysed the frequency of winter and summer temperature extremes at 11 sites in central and southern Europe (1901Europe ( -1998 and found large long-term fluctuations, with a slight warming trend, statistically significant only at a few stations. For the Mediterranean basin, based on the analysis of 15 different indices of temperature extremes, Efthymiadis et al (2011) found that the underlying trends are generally consistent with global trends of the temperature and its extremes: cold extremes decrease and warm/hot extremes increase. This consistency is better manifested in the western part of the Mediterranean where changes are the most enhanced since the mid-1970s.…”

“…Tomozeiu et al, 2002;Efthymiadis et al, 2011). The most recent circulation types developed by Philipp et al (2007), using a more stable statistical scheme, have also been used to justify the trends in extremes on European regions (Jones and Lister, 2009;Ionita et al, 2013).…”

“…In most cases, the relationship between circulation patterns and climate extremes have been detected through the simple correlation between the two data sets (e.g. Efthymiadis et al, 2011;Ionita et al, 2011), composite maps (e.g. Tomozeiu et al, 2002;Ionita et al, 2013) or through multivariate techniques such as the canonical correlation analysis (CCA) (Haylock and Goodess, 2004;Xoplaki et al, 2004;Della-Marta et al, 2007).…”