Abstract
This study analyses spatial variability and trends in annual and monthly precipitation (amount and concentration) based on data from 42 stations in mainland Portugal during the period 1960–2011. Relationships between certain geographic variables (elevation, latitude and longitude) and precipitation variability were also determined in order to check for specific dependencies and spatial patterns in precipitation distribution, concentration and changing trends. Trends and relationships have been analysed using both parametric and non-parametric tests.The results showed that annual precipitation had decreased in all stations and that this trend is statistically significant for most of the time series (70% of the stations showed negative trends with at least a 0.1 significance level). The Annual Precipitation Concentration Index revealed an opposite behaviour pattern, suggesting that even though the annual trend for precipitation amount was negative overall, more than half of the udometric stations registered a more marked seasonality for precipitation during the period 1960–2011. However, only one station showed statistical significant time trend. Regarding the influence of geographical features, latitude is the most important variable, governing spatial distribution and variations in annual precipitation as well as its intra-annual changeability. These important changes in precipitation, involving both amount and concentration, may have severe consequences for ecosystems and societies.
Highlights
Changes in the amount and intra-annual distribution of precipitation can have important environmental and economic effects
The altimetric gradient varies from 2 m to 1018 m. As these 42 rain gauges are used for monitoring precipitation on a national scale, the data were complied with important quality criteria, namely: (i) a limited number of gaps in the monthly time series, generally less than 1% of the total observation record longevity, (ii) the fact of being spatially representative of the distribution irregularity for precipiFigure 1 Location of the gauging stations used in this study tation in mainland Portugal, and (iii) normality and homogeneity requirements
In general the mean annual precipitation decreased from north to south and from the coastal region to inland Portugal, this behaviour was more evident in the north and centre of the country
Summary
Changes in the amount and intra-annual distribution of precipitation can have important environmental and economic effects. Variations in precipitation can limit ecosystem productivity, affect soil erosion In Portugal, as well as in the Mediterranean region in general, there is a complex pattern for spatial and seasonal variability in precipitation, aggravated by the inconstancy of rainfall from year to year and during the year. This inter-annual variability makes it difficult to assess trends in precipitation distribution patterns and the impact of potential climate change (Ramos and Martínez-Casasnovas, 2006)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
