STUDY OF GENERAL EFFECTS OF RIVER RUNOFF VARIATIONS

摘要

Time series of monthly mean water discharges from some rivers of Europe and the European part of the former USSR are analyzed. The aim of the analysis is to study the effects of general variability of the monthly mean river runoff which arise simultaneously in joint processing of the time series. A river system over large areas coupled with the atmospheric circulation, which affects the river runoff regime, can be considered as a large distributed nonlinear dynamic system. Therefore, it is interesting to study probable effects of interactions within this system. The effects of general variability (coherence) are determined using two procedures: by estimating the evolution of the Hurst constant for different rivers and by estimating the change in the spectral measure of coherence of variations in the specified frequency range. The spectral measure is calculated as a product of component-wise canonical coherences of a multivariate spectral matrix. As a result of analysis, low-frequency effects of general variability are found. Based on the comparison with spectral characteristics of the reconstructed winter mean temperatures for the last 1500 years, a hypothesis of the climatic origin of these variations is proposed.