Recent and future changes of precipitation extremes in mainland Portugal

Abstract

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 Portuguese municipalities, 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.