Abstract
<p>Improving the knowledge about the impacts of climate change on extreme drought events at basin scale, is important for decision makers in order to develop drought contingency plans which are the leading edge of adaptive management strategy. Considering high-resolution grids of observed daily rainfall and information provided by latest-generation Regional Climate Models (RCMs), the changes in the spatio-temporal patterns of extreme droughts in peninsular Spain are assessed. The non-stationarity character of time series, due to climate and anthropogenic changes, is represented by probabilistic models considering the time evolution of probability density function (PDF) parameters fitted to annual maximum lengths of dry spells time series. By a PDF ensemble from 17 RCMs, the spatio-temporal variability exhibited by the RCMs is represented. Scoring of models is based in the goodness-of-fit to CDFs (cumulative distribution functions) of observed annual maximum dry spells lengths. The reliability and skills of RCMs are assessed, for building the PDF ensemble, at grid site for the study area. Therefore, by adjusting PDF to series of annual maximum dry spells lengths, applying GAMLSS and bootstrapping techniques, the assessment of regional changes and trends associated to high returns periods (<em>Tr</em> = 25 and 50 yr.) is assessed. In general, an intensification of drought events for 2050 horizon, in contrast with 1990, is expected. By increasing return periods, the length of the annual maximum dry spells rises, albeit with a smaller number of areas with significant differences. The areas prone to extreme droughts in mainland Spain are identified.</p>
Highlights
Europe is regularly affected by severe water scarcity and drought events
The results provided by seventeen latest-generation Regional Climate Models (RCMs) driven by Global climate models (GCMs), from the European ENSEMBLES Project (Christensen, Rummukainen, & Lenderink, 2009) for the time period 1950–2050 under SRES A1B greenhouse gas and ozone recovery forcing scenarios are considered
A This study describes the variability and discontinuities detected in the spatial patterns of annual extreme dry spells in peninsular Spain, by non-stationary modelling and ensemble techniques of RCMs
Summary
Europe is regularly affected by severe water scarcity and drought events. Southern and south-eastern Europe is most prone to an increase in drought hazard, due to high demands of water. In southern Spain, agriculture accounts for more than 80 % of the total national abstraction In this sense, the plausible trends in the frequency and intensity of maximum drought events, and its potential impact on water availability, should be known. Since hydrological systems are affected by several drivers (land-use change, groundwater development, dam building, climate variability and change), today it is no longer possible to consider them as stationary (Milly et al, 2008) Considering these premises for building spatial distribution of annual maximum dry spells lengths associated to Tr, the GAMLSS (Generalized Additive Models for Location, Shape and Scale) tools proposed by Rigby and Stasinopoulos (2005), are applied. From the spatial patterns of plausible annual maximum dry spells lenghts associated with several Tr, and the time frame selected, quantitative predictions of climate change impacts on extreme drought risk at basin scale are assessed
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