Temporal fluctuations of seasonal precipitation in Jerusalem

The annual rainfall in Jerusalem during the period 1846–47 to 1953–54 is studied by the method of time spectrum analysis and filtering techniques. The effect of different methods of spectral presentations is then demonstrated. A prominent significant peak appears in the spectrum at a period of 3.0–3.3 years and a secondary peak is evident at 2.15 years. More than 55% of the total variance of annual rainfall in Jerusalem is concentrated in the period band between 2 and 4.3 years. The above two peaks were compared with published spectra of rainfall and other meteorological parameters in other parts of the world and found compatible with the Southern Oscillation (S.O.) and the Quasi Biennial Oscillation (Q.B.O.), respectively. When the data were subdivided into two equal subperiods, the 3.0–3.3 years' peak remained the dominant feature in both spectra, whereas the 2.15 years' peak disappeared altogether in the second subperiod. The implications of this behaviour are discussed.