Anomalous Extreme Rainfall Variability Over Europe - Interaction Between Climate Variability and Climate Change

Climate variability and change are expected to alter the frequency, intensity and duration of extreme rainfall and urban flooding, which in turn will pose challenges to the urban drainage systems and management. This study analyses the decadal variability of daily extreme rainfall at 263 European stations and its connection with North Atlantic Oscillation (NAO), Western Mediterranean Oscillation (WeMO) and Southern Oscillation Index (SOI) over a roughly centennial period (1925-2015). The impact of climate change on the linkage between the anomalies of extreme rainfall and atmospheric circulations is also investigated. The results show a strong imprint of winter NAO and summer WeMO on extreme rainfall variability in Europe, with significant relationships (alpha = 0.05) at 70% and 45% of the stations, respectively. About 10-15% of the significant relationships is because of the underlying trend in the anomaly series due to climate change. Further investigation of climate change impact on the linkage reveals that the significant positive trend (alpha = 0.05) in winter NAO and summer WeMO anomaly series is accompanied by the same trend in extreme rainfall anomaly series at 67% and 37% of the stations for winter and summer, respectively. These results provide new insights into the climate variability versus trends and corresponding changes in extreme rainfall.