A NOTE ON FLUCTUATIONS OF THE NILE RIVER FLOOD LEVELS (715-1470)

Climate episodes, lasting a century or longer, of low and high annual Nile flood level minima (from 715 to 1470) are defined by a lowpass filter. Their relation to fluctuations of shorter or longer periodicity (less than or greater than 25 years) is deduced from the power spectral density of a hundred year window moving over the time series. Low flood climate and enhanced variance of short period fluctuations are significantly correlated characterizing reduced persistence of fluctuations during dry climate conditions. There is only a qualitative indication of enhanced long period variability (or enhanced persistence) during high flood levels.