Wavelet analysis of some rivers in SE Europe and selected climate indices

Abstract

The influence of some climatic oscillations and sunspot number on river flows in Romania, Ukraine, and Moldova is verified by using standard wavelet analyses. The selected climate oscillations are Arctic Oscillation (AO), Antarctic Oscillation (AAO), East Atlantic Oscillation (EAO), East Atlantic/West Russia Oscillation (EAWRO), NINO3.4, North Atlantic Oscillation (NAO), Pacific/North America Oscillation (PNAO), Pacific Decadal Oscillation (PDO), Polar/Eurasia Oscillation (PEO), Scandinavian Oscillation (ScandO), Southern Oscillation (SO), and West Pacific Oscillation (WPO). Forty-five hydrological stations from an area of 45,000 km(2) were used in order to discover the spatial evolution of the periodicities found in rivers. The wavelet analysis is novel for the rivers in the study area. There is an important difference between the periodicities found in mountain and plateau areas and those found in the plain area. There is a general downstream increase in the confidence level of the identified periods, even if the atmospheric precipitation has more relevant periodicities in the mountain area. The periodicities can be grouped into two compact groups: 1-16.5 and 27.8-55.6 years. The correlation matrix of the global wavelet spectrum (GWS) values indicates that NAO, EAWRO, PDO, and the sunspot number are the main factors that generate the periodicities in rivers. It is the first time when the influence of PDO on local rivers is proven. All river periodicities smaller than 16 years have a confidence level of 0.95 or above, as proven by the GWS analysis of the daily discharge data, and are caused by multiple external factors.

Selection of Optimal Palmer Predictors for Increasing the Predictability of the Danube Discharge: New Findings Based on Information Theory and Partial Wavelet Coherence Analysis

“…In the present study, the results related to oscillations are consistent, for the most part, with the periodicities found in the paper [ 89 ] (Briciu and Mihaila, 2014). In the mentioned work, for South-East Europe, the influence of some climatic oscillations and sunspot number on river discharge in Romania, Ukraine, and Moldova was analyzed, by applying wavelet transform.…”

Statistical and Fractal Approaches on Long Time-Series to Surface-Water/Groundwater Relationship Assessment: A Central Italy Alluvial Plain Case Study

“…Thus, these two measures modulate the rainfall input signal, lowering the short period fluctuations and highlighting the long period ones (seasonal and multi-year) that are in association to large scale climatic oscillations, as many researchers have reported [59,79,[82][83][84][85][86][87].…”

A Spatiotemporal Approach in Detecting and Analyzing Hydro-climatic Change in Northwest Algeria

“…It should be noted that the semi-arid character of northern Algeria, particularly the western zone, is partly defined by the changes in the general atmospheric circulation. Several studies connect precipitation compression to the North Atlantic Oscillation (NAO), which impacts the Mediterranean climate [31][32][33][34][35][36]. The phenomenon is studied quantitatively by the NAO index, which describes a normalized pressure difference between the measurements made in the Azores and Iceland.…”