El índice NAO y la precipitación mensual en la España peninsular

A detailed analysis in a monthly basis of the correlation between a NAO index and the precipitation for peninsular Spain is made. The NAO index is calculated by means of Lisbon and Reykjavik sea surface pressure series. The monthly series of precipitation of 41 Spanish observatories for the period 1900-1994 are used. The results allow to distinguish four groups of months: (1) From October to March, with high negative correlation between the NAO index and the precipitation in the centre and the Southwest of peninsular Spain ‐this permits to regionalize the country into three regions; (2) April and May with less dependence of precipitation from NAO index; (3) the summer (June, July and August) without NAO signal; and (4) September, a transitional month between the summer and the months with clear NAO signal.