Atmospheric Dynamics Leading to West European Summer Hot Temperatures Since 1851

Figure 1

Summer SLP weather regimes over the North-Atlantic region and their dominance in the twenty warmest summers during 1871–2011 in Western Europe. (a)–(d) Summer SLP (hPa anomalies) weather regimes. (a) North-Atlantic oscillation in its negative phase (NAO−). (b) Atlantic Ridge (AR). (c) Blocking (BLO). (d) Atlantic Low (AL) weather regime. (e) Probability to find a dominant weather regime in all the warmest summers (EM and 56 members). (f) 24 warmest summers in Western Europe (colored region in (a)–(d)) with their dominant weather regime (20CRv2c EM). Circle size depends on temperature (anomalies), the largest the warmest. Colors represent the dominant weather regime for each summer based on the highest anomalous frequency. (g)–(j) Boxplots of daily weather regimes during the 24 warmest summers of 20CRv2c EM (as in (f)) in Western Europe separated by groups of 6 summers per 40 years: (g) shows group G1, (h) group G2, (i) group G3, and (j) group G4 1.