Regionalization Of Droughts In Portugal
Author(s)
J. F. Santos, M. M. Portela & I. Pulido-Calvo
Abstract
Droughts are complex natural hazards that distress large worldwide areas every
year with serious impacts on society, environment and economy. Despite their
importance they are still among the least understood extreme weather events.
This paper is focused on the identification of regional patterns of droughts in
Mainland Portugal based on monthly precipitation data, from September 1910 to
October 2004, in 144 rain gages distributed uniformly over the country. The
drought events were described by means of the Standardized Precipitation Index
(SPI) applied to different time scales. To assess the spatial and temporal patterns
of droughts, a principal component analysis (PCA) and K-means clustering
method (KMC) were applied to the SPI series. The study showed that, for the
different times scales, both methods resulted in an equivalent areal zoning, with
three regions with different behaviours: the north, the centre and the south of
Portugal. These three regions are consistent with the precipitation spatial
distribution in Portugal Mainland, which in general terms decrease from North to
South, with the central mountainous region representing the transition between
the wet north and the progressively dry south. As the mean annual precipitation
decreases southwards the hydrological regime becomes more irregular and
consequently more prone to droughts.
Keywords: Standardized Precipitation Index (SPI), principal component analysis
(PCA), clusters analysis.
1 Scope: data base
The present paper addresses the identification of spatial patterns of droughts in
Mainland Portugal by applying two procedures often utilized in regionalization
studies of climatic variables, namely the principal components analysis (PCA)
Keywords
Standardized Precipitation Index (SPI), principal component analysis (PCA), clusters analysis
Related Book
Other papers in this volume
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