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Ann. Geophys., 20, 2077-2085, 2002
www.ann-geophys.net/20/2077/2002/
© European Geosciences Union 2002
NAO influence on extreme winter temperatures in Madrid (Spain)
L. Prieto1, R. Garcia1, J. Diaz2, E. Hernandez1, and T. del Teso1
1Depto. Fisica de la Tierra II, Fac. CC. Fisicas, Univ. Complutense de Madrid, Spain
2Centro Universitario de Salud Publica, Universidad Autonoma de Madrid, Spain
Correspondence to: L. Prieto (luis@6000aire.fis.ucm.es)
Abstract. 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 nonlinear 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.
Key words. Meteorology and
atmospheric dynamics (climatology; synoptic-scale meteorology; general or
miscellaneous)
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