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Spatial and temporal variability of droughts in Portugal

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Resumo:An analysis 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 is presented. The drought events were characterized by means of the Standardized Precipitation Index (SPI) applied to different time scales (1, 6 and 12 consecutive months and 6 months from April to September and 12 months from October to September). To assess spatial and temporal patterns of droughts, a principal component analysis (PCA) and K means clustering (KMC) were applied to the SPI series. By this way three different and spatially well-defined regions with different temporal evolution of droughts were identified (north, central and south regions of Portugal). A spectral analysis of the SPI patterns obtained with principal component analysis and clusters analysis, using the fast Fourier transform algorithm (FFT), showed that there is a manifest 3.6-years cycle in the SPI pattern in the south of Portugal and evident 2.4-year and 13.4-year cycles in the north of Portugal. The observation of the drought periods supports the occurrence of more frequent cycles of dry events in the south (droughts from moderate to extreme approximately every 3.6 years) than in the north (droughts from severe to extreme approximately every 13.4 years). These results suggest a much stronger immediate influence of the NAO in the south than in the north of Portugal, although these relations remain a challenging task.
Autores principais:Pulido-Calvo, Inmaculada
Outros Autores:Portela, Maria Manuela; Santos, João
Assunto:Standardized Precipitation Index (SPI) Principal component analysis (PCA) Clusters analysis Fast fourier transform (FFT)
Ano:2010
País:Portugal
Tipo de documento:artigo
Tipo de acesso:acesso aberto
Instituição associada:Instituto Politécnico de Beja
Idioma:inglês
Origem:Repositório Institucional do IPBeja

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