• winter warm events;
  • climatic indices;
  • trends;
  • regional climate models;
  • Ebro basin;
  • Iberian Peninsula


In this study we analyze the observed trends for the period 1950–2006 in a number of climate indices related to the occurrence of winter warm events in the Ebro basin, northeast Iberian Peninsula. Climatic simulations using 12 regional climate models (RCMs) from the ENSEMBLES database enable calculation of the multi-model means for the projected evolution of these climatic indices for the time periods 2021–2050 and 2051–2080. The results based on observations indicate a significant increase in occurrence of warm and very warm days and nights, melting events at 2000 m a.s.l. and the duration of warm spells across most of the study area. The number of warm spells comprising at least five consecutive warm days or nights also tends to increase, although the trend is not statistically significant for many of the observatories involved in the study. The RCMs project that the trends observed during the observation period will continue, and that the occurrence of warm day and night events and spells are very likely to increase during this century. In some cases the occurrence of warm events is projected to double during the period 2021–2050, and continue increasing for the period 2051–2080. For both the observed and projected periods, most of the indices show a greater increase in the occurrence of these events in the mountain areas of the basin (the Pyrenees and the Iberian mountains). Copyright © 2013 Royal Meteorological Society