Wavelet and scaling analysis of monthly precipitation extremes in Germany in the 20th century: Interannual to interdecadal oscillations and the North Atlantic Oscillation influence

Monthly precipitation extremes from gauging stations across Germany were studied using continuous wavelet tools toward variance and frequency-time localization and detection of dominant oscillations. Apart from the high-frequency, 1 year oscillation, the monthly precipitation extremes show enhanced power at interannual (7-8 years) and/or interdecadal (11-14 years) low-frequency scales, in particular in the second part of the 20th century, providing evidence for some regional climatic changes over Germany. Applying detrended fluctuation analysis (DFA), scaling properties of the precipitation time series through the computation of the Hurst parameter are determined. It is apparent that data with low-frequency components, regardless of whether significant or not, show higher Hurst parameter values, that is, some amount of persistence, than data without such components. Through analyses of the scale-averaged wavelet power and the cross-wavelet spectra, evidence for a teleconnective influence of the North Atlantic Oscillation on the precipitation pattern, primarily over the last 40 years, and with partly opposite effects in the northern and southern parts of Germany, is found. As such, the North Atlantic Oscillation phase of enhanced decadal variability was shown to be responsible for the low-frequency precipitation components.