Water in Celtic Countries: Quantity, Quality and Climate Variability (Proceedings of the Fourth InterCeltic Colloquium on Hydrology and Management of Water Resources, Guimarães, Portugal, July 2005). IAHS Publ. 310, 2007, 94-102.

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Precipitation trends in mainland Portugal in the period 1941–2000

M. ISABEL P. DE LIMA^1,2, ANA C. P. MARQUES¹, JOÃO L. M. P. DE LIMA^1,3 & M. FÁTIMA E. S. COELHO⁴

1 Institute of Marine Research/IMAR-Sea, Environment and Territory Research Centre, Portugal

2 Forestry Department, ESAC/Polytechnic Institute of Coimbra, Bencanta, 3040-316 Coimbra, Portugal

iplima@esac.pt

3 Department of Civil Engineering, FCTUC, University of Coimbra, Pólo II, 3030-290 Coimbra, Portugal

4 Institute of Meteorology, Rua C ao Aeroporto, 1749-077 Lisboa, Portugal

Abstract The presence of a trend in hydrological parameters can result from the highly variable nature of hydrological processes or be related to climate variations. The purpose of this work is to contribute to a better understanding of the variability of precipitation by investigating recent trends in the temporal structure of this process in mainland Portugal. The study uses annual and monthly precipitation data from 107 locations scattered over the territory. The time span of the records is 60 years, from 1941 to 2000. The data are analysed using statistical methods (e.g. Mann-Kendall trend test). In order to take into account seasonality and serial correlation, the months of the year were analysed separately. The analyses of both annual and monthly data led to a characterization of changes in the distribution of precipitation over mainland Portugal and within the year.

Key words climate change; mainland Portugal; precipitation; seasonality; trend

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