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Propriedades da geoinformação de uso e ocupação do solo na modelação e análise ambiental
Publication . Meneses, Bruno; Reis, Eusébio Joaquim Marques dos; Vale, Maria José Correia Botelho Soares de Oliveira Lucena e
Recent and future changes of precipitation extremes in mainland Portugal
Publication . Santos, Mónica; Fonseca, André; Fragoso, Marcelo; Santos, João A.
Recent and future changes in precipitation extremes over Portugal were studied. Trends in selected precipitation indices were
calculated on a seasonal scale for the period of 1950–2003. Considering the same indices, this study also assessed possible
changes under future climatic conditions (2046–2065). Furthermore, trends and projections for the future were evaluated using a
single/unified index of extreme precipitation susceptibility (EPSI). The results revealed statistically significant drying trends in
spring, mainly in northern and central Portugal, while weak wetting trends were detected in autumn. The EPSI trends also
depicted a decrease of extreme precipitation in spring over central Portugal and a slight increase in autumn over northern Portugal
and nearby Lisbon. On the other hand, climate change projections revealed a decrease in precipitation, mainly over northwestern
Portugal, whereas the contribution of extreme precipitation to total precipitation is expected to increase, mostly in southern
Portugal. The maximum number of consecutive dry days (CDD) is also projected to increase throughout Portugal. EPSI showed
enhanced susceptibility for most Portuguesemunicipalities, which may be associated with increased vulnerability to flash floods.
Climate change projections by municipality for both EPSI and CDD are an important decision support tool for civil protection
and for risk management in Portugal.
A Century and Half of Hydrogeomorphological Disasters in Mainland Portugal
Publication . Zêzere, José Luís; Pereira, Susana; Santos, Pedro P.; Fernandes, F.; Malheiro, A.; Chaminé, Helder
Regional rainfall thresholds for landslide occurrence using a centenary database
Publication . Vaz, Teresa; Zêzere, José; Pereira, Susana; Oliveira, Sérgio Cruz; Garcia, Ricardo A. C.; Quaresma, Ivânia
This work proposes a comprehensive method to assess rainfall thresholds for landslide initiation using a centenary landslide database associated with a single centenary daily rainfall data set. The method is applied to the Lisbon region and includes the rainfall return period analysis that was used to identify the critical rainfall combination (cumulated rainfall duration) related to each landslide event. The spatial representativeness of the reference rain gauge is evaluated and the rainfall thresholds are assessed and calibrated using the receiver operating characteristic (ROC) metrics.
Results show that landslide events located up to 10 km from the rain gauge can be used to calculate the rainfall thresholds in the study area; however, these thresholds may be used with acceptable confidence up to 50 km from the rain gauge. The rainfall thresholds obtained using linear and potential regression perform well in ROC metrics. However, the intermediate thresholds based on the probability of landslide events established in the zone between the lower-limit threshold and the upper-limit threshold are much more informative as they indicate the probability of landslide event occurrence given rainfall exceeding the threshold. This information can be easily included in landslide early warning systems, especially when combined with the probability of rainfall above each threshold.
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
3599-PPCDT
Número da atribuição
PTDC/ATP-GEO/1660/2014