,- Institute of Geodynamics, Romanian Academy, Bucharest, Romania (ileana_mares@geodin.ro)
The aim of this study is to explore links between large-scale atmospheric circulation and meteorological and hydrological drought events in the Danube basin.
Based on previous studies on the relationship between large-scale atmospheric circulation and the occurrence of extreme events in the Danube basin, especially in the middle and lower Danube basin, two climate indices were considered. The first index characterizes the Greenland-Balkan Oscillation (GBOI) and the second is the well-known index associated with the North Atlantic Oscillation (NAOI). For meteorological and hydrological drought, the Palmer Drought Severity Index (PDSI), with applications especially in the agricultural field, and, respectively, the Palmer Hydrological Drought Index (PHDI), especially useful for estimating drought affecting water resources on longer timescales, were taken into account.
To find the type of connection (linear/non-linear) between large-scale climate indices (GBOI, NAOI) and those at the regional scale (PDSI, PHDI), elements from information theory, such as mutual information, were applied. To get time-frequency details, bivariate and multivariate wavelet transforms were used.
The analyses were performed separately for each season. The most statistically significant results were obtained both for the link between GBOI and PDSI, in the winter season, and for that between GBOI and the two analysed Palmer indices, in the spring season.
Regarding the influence of NAOI, it is much less than that of GBOI, but it can be considered relatively significant in winter on PDSI and in spring on PHDI.
From the wavelet coherence analyses it was observed that the significant coherences between the large-scale atmospheric indices and the analysed Palmer drought indices are located in frequency bands, corresponding to ~11–year, 22-year and 33-year period bands, that can be associated with the Schwabe, Hale and even Bruckner solar activity cycles.
In exploring regional-scale droughts, for the future studies, it appeared evident the importance of taking into account of the simultaneous or delayed influence of solar activity on terrestrial climate variables.
How to cite: Mares, C., Mares, I., Dobrica, V., and Demetrescu, C.: On the links between large-scale atmospheric circulation and extreme events in the Danube basin, identified by Palmer drought indices, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10629, https://doi.org/10.5194/egusphere-egu26-10629, 2026.
