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Euro-Cordex regional projection models: what kind of agreement for Europe?

Martins, Ana; Rafael, Sandra; Monteiro, Alexandra; Scotto, Manuel; Gouveia, Sónia

Mathematical Geosciences, 51 (2019), 1021-1035

Euro-Cordex is an international initiative which provides regional climate projections based on multiple dynamical and empirical-statistical downscaling models. The goal of
this work is to analyse the agreement between projections of the CLMCOM-CCLM4-8-17 (CLMCOM) and SMHI-RCA4 (SMHI) models across Europe. The variables temperature, precipitation and solar radiation were considered for the historical period (1971-2005) and for a future scenario (2006-2040). Overall agreement (A) is defined as the normalised area of the magnitude-squared coherence function over the frequency range (averaged over time), being zero for no agreement and one for total agreement between models. Relative mean difference (M) and the difference between the coefficients of variation (V) are also explored as coherence analysis cannot evaluate existing differences in mean and variability. Agreement values on the range 0.32-0.74, 0.28-0.69 and 0.32-0.58 were found for temperature, precipitation and solar radiation, respectively, at the historical period. In all cases, results show that agreement is higher for lower frequencies than for higher frequencies. Overall, time series from both models behave fairly similar for lower frequencies (i.e. the trend of the time series), while for higher frequencies (i.e. rapid changes in the time series), models similarities are less consistent. For temperature, M and V values are smaller than 2.5%, while for precipitation and solar radiation those values can reach values higher than 50% and 35%, respectively. Further analysis, revealed that the contribution of Winter and Summer differs considerably to M and V values. In conclusion, it seems that such models are able to provide fairly similar results when considering large periods of time.