NAO influence on extreme winter temperatures in Madrid (Spain)

• Published in: Annales Geophysicae
• Main Authors: Prieto, L., García Herrera, Ricardo, Díaz, J., Hernández Martín, Emiliano, Teso, T. del
• Format: Article in Journal/Newspaper
• Language: English
• Published: European Geophysical Society 2002
• Subjects: Astrofísica; Astronomía; North Atlantic; North Atlantic oscillation
• Online Access: https://eprints.ucm.es/id/eprint/34825/; https://eprints.ucm.es/id/eprint/34825/1/garciaherrera79libre.pdf; https://doi.org/10.5194/angeo-20-2077-2002

Extremely cold days (ECDs), with minimum temperatures lower than -4.6°C, have been analysed for Madrid. This threshold corresponds to the 5th percentile of the period 1963-1999. Adopting a case analysis approach, five synoptic patterns have been identified that produce these extremely low temperatures. Three of them are associated with cold air flows over the Iberian Peninsula, and the other two with a lack of significant circulation over the region. A non-linear association with the North Atlantic Oscillation (NAO) has been identified using log-linear models. The NAO positive phase leads to an increase in the winter frequency of those synoptic patterns associated with stagnant air flow over Iberia, while those characterised by cold, northern flows do not appear to be similarly influenced.