Heatwaves in Europe: areas of homogeneous variability and links with the regional to large-scale atmospheric and SSTs anomalies
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This work presents a methodology to study the interannual variability associated with summertime months in which extremely hot temperatures are frequent. Daily time series of maximum and minimum temperature fields (T max and T min, respectively) are used to define indexes of extreme months based on the number of days crossing thresholds. An empirical orthogonal function (EOF) analysis is applied to the monthly indexes. EOF loadings give information about the geographical areas where the number of days per month with extreme temperatures has the largest variability. Correlations between the EOF principal components and the time series of other fields allow plotting maps highlighting the anomalies in the large scale circulation and in the SSTs that are associated with the occurrence of extreme events. The methodology is used to construct the “climatology” of the extremely hot summertime months over Europe. In terms of both interannual and intraseasonal variability, there are three regions in which the frequency of the extremely hot days per month homogeneously varies: north-west Europe, Euro-Mediterranean and Eurasia region. Although extremes over those regions occur during the whole summer (June to August), the anomalous climatic conditions associated with frequent heatwaves present some intraseasonal variability. Extreme climate events over the north-west Europe and Eurasia are typically related to the occurrence of blocking situations. The intraseasonal variability of those patterns is related to the amplitude of the blocking, the relative location of the action centre and the wavetrain of anomalies downstream or upstream of the blocking. During June and July, blocking situations which give extremely hot climate conditions over north-west Europe are also associated with cold conditions over the eastern Mediterranean sector. The Euro-Mediterranean region is a transition area in which extratropical and tropical systems compete, influencing the occurrence of climate events: blockings tend to be related to extremely hot months during June while baroclinic anomalies dominate the variability of the climate events in July and August. We highlight that our method could be easily applied to other regions of the world, to other fields as well as to model outputs to assess, e.g. the potential change of extreme climate events in a warmer climate.
KeywordsExtreme events Heatwaves Temperature variability Climate variability
First author was partially supported by MERSEA (SIP3-CT-2003-502885) and ENSEMBLES (GOCE-CT-2003-505539) European funding projects.
- Beniston M (2004) The 2003 heatwave in Europe: a shape of things to come? An analysis based on Swiss climatological data and model simulations. Geophys Res Lett 31:L02202. doi:10.1029/2003GL018857Google Scholar
- Black E, Blackburn M, Harrison RG, Hoskins BJ, Methven J (2004) Factors contributing to the summer 2003. Eur Heatwave Weather 59(8):217–223. doi:10.1256/wea.74.04Google Scholar
- Bolle HJ (2002) Climate, climate variability and impacts in the Mediterranean area: an overview. In: Bolle HJ (ed) Chapter 2 in mediterranean climate. Springer, BerlinGoogle Scholar
- Della-Marta PM, Luterbacher J, von Weissenflush H, Xoplaki E, Brunet M, Wanner H (2007) Summer heat waves over western Europe 1880–2003, their relationship to large scale forcings and predictability. Clim Dyn (in press). doi: 10.1007/s00382-007-0233-1
- Grazzini F, Viterbo P (2003) Record-breaking warm sea surface temperature of the Mediterranean Sea. ECMWF Newsl 98:30–31Google Scholar
- IPCC (2001) Climate change. The IPCC 3rd assessment report. Volumes I (Science), II (Impacts and Adaptation) and III (Mitigation Strategies). Cambridge University Press, CambridgeGoogle Scholar
- Liebmann B, Smith CA (1996) Description of a complete (interpolated) outgoing longwave radiation data set. Bull Am Met Soc 77:1275–1277Google Scholar
- Nakamura M, Enomoto T, Yamane S (2005) A simulation study of the 2003 heatwave in Europe. J Earth Simulator 2:55–69Google Scholar
- Spiegel MR, Stephens LJ (1961) Theory and problems of statistics. Schaum’s outlines of, McGraw Hill, New YorkGoogle Scholar
- Xoplaki E, Gonzalez-Rouco JF, Gylistras D, Luterbacher J, Rickli R, Wanner H (2003a) Interannual summer air temperature variability over Greece and its connection to the large-scale atmospheric circulation and Mediterranean SSTs 1950–1999. Clim Dyn 20:537–554Google Scholar
- Xoplaki E, Gonzalez-Rouco JF, Luterbacher J, Wanner H (2003b) Mediterranean summer air temperature variability and its connection to the large-scale atmospheric circulation and SSTs. Clim Dyn 20:723–739Google Scholar