EUCLIPSE First Period Report

Figure 4. Evaluation and analysis of the occurrence of temperature extremes during summer
predicted by the IPSL-CM5A-LR climate model over Europe: the difference between the
frequency of temperature extremes predicted by the model and that derived from observations
(E-OBS) is shown for four predominant weather regimes (Blocking or BL, NAO-, Atlantic Ridge
or AR, and Atlantic Low -or AL), and decomposed in two main contributions: one related to
differences in the occurrence of the weather regimes themselves (“Inter”), one related to
differences in the physical conditions associated with each regime (“Intra”). The second-order
residuals are indicated by “Res”. The figure shows that the model tends to overestimate the
severity of heat waves over central Europe and to underestimate it elsewhere, and that most
of the difference with observations comes from the physical conditions (e.g. the cloud cover)
predicted by the model under specified weather regimes rather than from differences in the
occurrence of the weather regimes themselves. Preliminary study from Cattiaux et al.
(personal communication).
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