Fingerprinting the North-Atlantic and Arctic oscillation signals in rainfall and new snowpack in the western Carpathian Mountains

Abstract

Time-varying relationships between two atmospheric oscillation modes and precipitation (rainfall and snow) in the western portion of the Carpathian Mountains and the northern part of the Pannonian Plain are investigated in this paper. The Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO) modes were used to explain the intra-annual variability of monthly rainfall totals and new snow over a 36-year period (1981–2017) observed at a dense network of 177 rain gauges and 33 snow rods located throughout the investigated area, respectively. The Continuous Wavelet Transform (CWT) was deployed as a band-pass filter to quantify the spectral coherence and attribution (based on signal-to-noise ratio) of the NAO and AO modes to the precipitation variability. The temporal and spatial patterns of NAO and AO-related signal variance in monthly rainfall totals and fresh snowpack were evaluated on seasonal and monthly bases. The NAO mode explained the major historically observed snow calamities, such as the snowy cold spell of January 1985 that hit central and southern Europe, bringing heavy snowfall to the investigated region and many other parts of Europe. This event was the beginning of a prolonged cold wave in Europe, with extremely low air temperatures across the continent. Our analyses showed that the AO mode appears to have only a limited effect on the overall variability of new snowpack in late winter. The attribution of NAO and AO modes to the variability of monthly rainfall totals is less pronounced compared to new snowpack.