Hydrological drought variability and its teleconnections with climate indices

In this study, the spatial–temporal variability of hydrological drought in Meriç Basin, Turkey, has been examined, and its relationship with global climate oscillations has been explored. Prior to drought analysis, streamflow data gaps were filled, and series homogeneity was examined. The standardized streamflow index (SSFI) was used to detect drought periods from monthly streamflow data of nine stations well spread over the study area. The hydrological drought intensity, magnitude, and duration were investigated using the SSFI time series. The drought variability was assessed by performing trend analysis and wavelet transforms. Trend analysis showed an increase in drought events in the Northern region and a decrease in the Southern region of the basin. Wavelet analysis reveals that the 4–10 year scales explicate the drought series pattern. The identification of climate patterns that are most associated with drought variability is performed via correlation analysis. The investigation showed that distinct climate patterns simultaneously influence drought events. Significantly, the influence of El Nino Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), and Atlantic Multidecadal Oscillation (AMO) is notable. The analysis demonstrated a remarkable correlation between ENSO and SSFI series at the interannual scale (2–8 years). The obtained phase difference suggests that the maximum dry (wet) conditions coincide with La Nina (El Nino) events. In addition, positive NAO phases and negative AMO phases lead to drought occurrence.