Daily rainfall affinity areas in Mediterranean Spain

A subdivision of the Spanish Mediterranean region into daily rainfall affin ity areas was conducted using a pluviometric data base of 410 gauges for th e period 1964-1993. Areas were derived using principal components analysis on the between-site correlation matrix. Two regionalizations defining 12 ar eas are offered: the first, non-overlapping, solution is derived by cluster analysis on the most important unrotated PCs extracted, while the second, with overlapping pluviometric regions, is obtained by mapping the obliquely rotated principal components. Both solutions are similar, and emphasize th e dominant role exerted by the complex topography of the region on the spat ial organization of rainfall through its interaction with the main rain-bea ring airflows and systems. A higher-resolution regionalization comprising 2 0 non-overlapping areas is also included. South and southeast domains, wher e topography is very prominent and complex, as well as the Balearic Islands , contain most of the additional detail offered by this solution. Copyright (C) 1999 Royal Meteorological Society.