Interannual variability of precipitation distribution patterns in Southern Portugal

Abstract

Southern Portugal is characterized by an irregular distribution of precipitation which is highly variable from year to year, requiring a clear ascertaining if the pattern of the precipitation is changing due to climate variability or climate change.In this paper, the authors applied several statistical methods to annual and seasonal time series of precipitation during the period 1931-2006, in order to detect trends and evaluate the variability in the frequencies of occurrence of dry and wet periods and also to assess spatial distribution patterns.The statistical methods include homogeneity tests, Mann-Kendall test, simple moving averages and cluster analysis. In spring, the authors detected a lack of homogeneity in the precipitation time series and a significant decreasing trend of precipitation was identified, by using simple moving averages and the Mann-Kendall test.Cluster analyses also confirmed the results and identified significant trends in the interannual and spatial distributions of dry, normal and wet years. It is concluded that the annual precipitation regime in the North interior sector is becoming drier, as the winter and spring also become drier. The only season in which a precipitation increase is observed is at fall and near the sea, but even for that region springs are also becoming drier.

Drought impact on carbon and water cycling in a Mediterranean <i>Quercus suber</i> L. woodland during the extreme drought event in 2012

“…In the recent past, precipitation shows a significant decrease in rain amount in February and March as well as a decrease in total annual rainfall on the Iberian Peninsula (Guerreiro et al, 2013;García-Barrón et al, 2013;Mourato et al, 2010;Paredes et al, 2006). A trend towards extreme events in the form of droughts is observed due to a more heterogeneous distribution of precipitation throughout the year (Zeppel et al, 2014;García-Barrón et al, 2013).…”

Water Availability in Southern Portugal for Different Climate Change Scenarios Subjected to Bias Correction

“…It clearly shows a generalised projected runoff reduction relative to the "Reference" simulation. The severe reduction in March may be a consequence of the severe decline in precipitation already observed in this particular month and referred by Mourato et al (2010). The largest range of results occurs in winter, the season is characterised by a higher runoff values.…”

“…The 35 udometric stations with daily precipitation records used in this paper are selected according to Mourato et al (2010). Average daily temperature records are obtained from 22 meteorological stations.…”

A Historical Analysis of Rainfall Trend in the Olifants Basin in South Africa

“…The non-parametric Mann-Kendall (MK) test which is based on the null hypothesis (H 0 ) of the absence of a trend as opposed to the alternative hypothesis (H 1 ) of the presence of a trend was used in the trend detection analysis. This method is preferred and highly recommended by the World Meteorological Organisation (WMO) for trend detection analysis (Mourato et al, 2010) due to the advantage it offers in its applicability irrespective of the data distribution function present in the time series data (Smith, 2000;Mourato et al, 2010). The MK test is briefly discussed herein but one is referred to Mann (1945) and Kendall (1948) for further details on the method.…”