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Abstract(s)
Grande parte do nordeste de Portugal é composta por zonas áridas, caracterizadas
por uma suscetibilidade de moderada a severa à desertificação e à seca. Foi realizada
uma análise de tendências, tanto individual quanto combinada, da precipitação e do
índice de seca SPI em vinte estações meteorológicas no Distrito de Bragança, em
Portugal, abrangendo um período de quarenta anos (1957-1997). A análise revelou
que, ao longo do período de estudo, à medida que a escala temporal do SPI aumentou
(de 1 para 12 meses), houve um aumento na frequência de meses secos, bem como
na ocorrência de meses com secas severas e extremas. Os resultados indicam uma
redução gradual ao longo da escala temporal, dos meses classificados como
‘’Próximo ao normal’’ na classificação de SPI, passando de 69% no SPI 1 para 65,5%
no SPI 12. Em contrapartida, a percentagem de meses de secas aumentou
gradualmente, com valores passando de 14,3% dos meses de seca no SPI 1 a 17%
no SPI 12. A percentagem de meses de ‘’seca severa’’ e ‘’seca extrema’’ seguiram o
mesmo padrão de aumento dos meses secos, aumentando conforme a escala de
análise de SPI 1 a SPI 12. No geral, as tendências identificadas para precipitação e
seca sugerem uma intensificação gradual na vulnerabilidade à desertificação na
região, embora sem um padrão de variação uniforme na região ao longo das 4
décadas estudadas.
Much of northeastern Portugal is arid, characterized by moderate to severe susceptibility to desertification and drought. An individual and combined trend analysis of precipitation and the SPI drought index was performed at twenty meteorological stations in the Bragança District of Portugal, covering a forty-year period (1957–1997). The analysis revealed that, over the study period, as the SPI time scale increased (from 1 to 12 months), there was an increase in the frequency of dry months, as well as in the occurrence of months with severe and extreme droughts. The results indicate a gradual reduction over the time scale of months classified as ‘’Near normal’’ in the SPI classification, going from 69% in SPI 1 to 65.5% in SPI 12. In contrast, the percentage of drought months increased gradually, with values going from 14.3% of drought months in SPI 1 to 17% in SPI 12. The percentage of months of ‘’severe drought’’ and ‘’extreme drought’’ followed the same pattern of increase as dry months, increasing as the scale of analysis from SPI 1 to SPI 12. Overall, the trends identified for precipitation and drought suggest a gradual intensification in vulnerability to desertification in the region, althoug
Much of northeastern Portugal is arid, characterized by moderate to severe susceptibility to desertification and drought. An individual and combined trend analysis of precipitation and the SPI drought index was performed at twenty meteorological stations in the Bragança District of Portugal, covering a forty-year period (1957–1997). The analysis revealed that, over the study period, as the SPI time scale increased (from 1 to 12 months), there was an increase in the frequency of dry months, as well as in the occurrence of months with severe and extreme droughts. The results indicate a gradual reduction over the time scale of months classified as ‘’Near normal’’ in the SPI classification, going from 69% in SPI 1 to 65.5% in SPI 12. In contrast, the percentage of drought months increased gradually, with values going from 14.3% of drought months in SPI 1 to 17% in SPI 12. The percentage of months of ‘’severe drought’’ and ‘’extreme drought’’ followed the same pattern of increase as dry months, increasing as the scale of analysis from SPI 1 to SPI 12. Overall, the trends identified for precipitation and drought suggest a gradual intensification in vulnerability to desertification in the region, althoug
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Keywords
Variabilidade climática Tendências temporais Seca Desertificação Extremos de precipitação SPI