Analysis of the exceptionally warm December 2015 in France using flow analogues
Résumé
Capsule December 2015 in France was an extreme of circulation and temperature. Both circulation and climate change partly explain the 4°C anomaly. We found no link between climate change and circulation. The event The December 2015 average temperature broke a record in France, with an anomaly of +4.1°C (Fig. 1a) with respect to the 1949-2015 climatology. The linear trend of average December temperature (in red in Fig. 1a) is not significant (p-value > 0.05), as regional temperature variability is high in winter. Such a positive temperature anomaly has impacts on the vegetation cycle (the French press covered this topic in the daily newspaper Le Monde 1). It also affects local economies, e.g. tourism in ski resorts. The temperature anomaly was concomitant with a zonal atmospheric circulation over Western Europe (Fig. 1b), directing mild subtropical air masses towards France. We found that the mean monthly SLP (sea level pressure) anomaly over the black box of Fig.1b is also a record high for the NCEP reanalysis. Such a circulation type generally leads to warm temperatures overs France (Yiou and Nogaj, 2004). In this paper we seek to address three questions: How much does the circulation anomaly explain the temperature anomaly during December 2015 in France? What is the influence of climate change on the occurrence of the circulation anomaly? How does the distribution of temperature conditional to the atmospheric circulation evolve with climate change?
Domaines
Sciences de l'environnement
Origine : Fichiers produits par l'(les) auteur(s)
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