SINGULAR SPECTRAL-ANALYSIS OF HOMOGENEOUS INDIAN MONSOON (HIM) RAINFALL

Homogeneous Indian Monsoon region rainfall for the epoch 1871-1990 has been analysed using Singular Spectral Analysis. It is shown that the HIM time series is simple in structure with only the annual oscillatio n and its first two harmonics accounting for almost the entire variabi lity. Longer period oscillations related to lunar tidal forcing, solar activity and quasibiennial variation are conspicuously absent. It is also shown that the singular spectral decomposition is closely similar to complex demodulation and thus provides variations in the signals w hich evolve only slowly with time. As the rainfall series is marked by several jerky changes, predictability of HIM rainfall through the pri ncipal components derived from SSA appears impossible.