Spatial–temporal dynamics of precipitation extremes in southern Portugal: a geostatistical assessment study

Abstract

Most of the recent studies and projections of precipitation patterns, based on records observed in the past and climate change scenarios for the Mediterranean basin, suggest a relatively slow decrease in rainfall amounts over the years but an increase in the frequency of extreme precipitation events. These are key factors in desertification processes and these will cause social and environmental impacts in the short term, mainly because changes in heavy rainfall events may have severe implications and impacts on soil erosion, resulting in increased risk of soil degradation.The main objective of the present work is to evaluate the spatial-temporal dynamics of extreme precipitation events in southern Portugal, using a direct sequential simulation algorithm (DSS models) in order to assess the relationships between spatial and temporal extreme rainfall patterns. Local probability density functions (pdfs) and spatial uncertainty are evaluated by a set of equiprobable simulated images of the chosen extreme precipitation indices.The used dataset in this work comprises a set of 105 station records of observed daily precipitation within the period 1961-2000. Two indices of extreme precipitation were selected: one representing the frequency of extremely heavy precipitation events (R30) and another characterizing the occurrence of dry events (RL10), both obtained from observed daily precipitation series.Results show that the spatial continuity of extreme precipitation events has increased in the last 40 years in southern Portugal. It also demonstrates a decrease in spatial variability, implying that extreme precipitation events tend to be more spatially homogeneous, which may have a severe impact on water resources, agriculture and soil erosion, particularly when associated with desertification risks.

Damaging Hydrogeological Events: A Procedure for the Assessment of Severity Levels and an Application to Calabria (Southern Italy)

“…In Calabria (southern Italy), some authors (e.g., [23]), considering an observation period of 100 years, have shown a negative trend in the heavy precipitation events, and an opposite trend in the low precipitation events. Generally, daily precipitation is studied using approaches based on indices, percentiles, thresholds, and extreme values [21,[24][25][26]. Two approaches are available when focusing on changes in extreme rainfall.…”

Recent trends in daily temperature extremes over southern Montenegro (1951–2010)

“…There has been considerable interest in the study of temperature and precipitation extremes at different scales (Zolina, 2008;Durao et al, 2010;Ceasar et al, 2011) due to their great impact on agriculture, water resources, industry, environment, and society. Since temperature records show an increase in the global mean temperature between 0.4 and 0.8 • C in the last 100 yr (IPCC, 2007), studies of extreme temperature events have raised the interest of the scientific community.…”

Daily precipitation concentration across Europe 1971–2010

“…A great deal of research has been carried out on daily precipitation, focusing on extreme events by means of a very heterogeneous spectrum of analysis methods, such as indices, percentiles, thresholds, and extreme value theory (Groisman et al, 2005), and it is not easy to compare different results (see discussions in Reiser and Kutie, 2010;Toreti et al, 2010;and Durao et al, 2010 among others for definitions and concepts). However, little information is available on the daily concentration of precipitation, mainly because of lack of high quality daily precipitation datasets (Brunetti et al, 2000(Brunetti et al, , 2001(Brunetti et al, , 2004Brugnara et al, 2012;Reiser and Kutiel, 2010).…”

“…across the Mediterranean basin (Norrant and Douguedroit, 2006;Moberg et al, 2006;Gallego et al, 2006;Brunet et al, 2007;Rodrigo and Trigo, 2007;Durao et al, 2010;Toreti et al, 2010). Thus, Reiser and Kutiel (2010) concluded that no generalized temporal changes have been detected in the daily rainfall regime across the Mediterranean basin, but the results depend on density of observations, study period, and area analysed; therefore, several trends in the probability of various daily rainfall categories have been suggested (Rodrigo, 2010).…”