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Seasonal assessments of future daily precipitation extremes in the Mediterranean area under consideration of non-stationarities within the predictor-predictand relationships

Christian Merkenschlager*, Elke Hertig

*Corresponding author:

ABSTRACT: Within the context of analyzing daily heavy precipitation events in the Mediterranean under enhanced greenhouse gas forcing in the 21st century a new method considering non-stationarities within the relationships of large-scale circulation predictors and regional precipitation extremes was applied. The Mediterranean area was split into up to 22 precipitation regions and analysis were performed for three different seasons (autumn, winter and spring) and quantiles (90th, 95th and 99th quantile), separately. Estimations are based on a Three-Step Censored Quantile Regression. Future estimations are performed by means of three model runs of the Earth System Model of the Max-Planck-Institute with Low Resolution (MPI-ESM-LR) for the representative concentration pathways (RCP) 4.5 and 8.5. Overall, the Mediterranean is mainly characterized by decreasing quantile values. Especially the regions in the southeast exhibit significant declines with up to 71.7% (-1.65mm) in the Levante region (autumn) and over 16mm (-38.2%) on Crete (winter). Increased precipitation quantiles were only assessed for a more or less extended region in the northern parts of the Central Mediterranean (winter and spring), for the northeastern coast of the Iberian Peninsula (autumn) and for the northern parts of Spain (spring). Overall, analysis have shown that non-stationarities seriously affect precipitation behavior in most parts of the Mediterranean. It turned out that two different regimes (western and eastern regime) inducing non-stationarities are predominant within the Mediterranean area. In autumn (winter), the western (eastern) regime is limited to the Iberian Peninsula (Levante) whereas in spring the area of influence of both regimes is rather of equal size.