A recently developed non-deterministic cell dynamic system model for atmospheric flows is summarized in this paper. The model predicts quantum-like mechanics for atmospheric flows with inherent long-range spatiotemporal correlations, now identified as signatures of self-organized criticality or deterministic chaos. The model enables quantification of the power spectrum of temporal fluctuations of atmospheric flows in terms of the universal and unique characteristics of the statistical normal distribution. The model predictions are in agreement with continuous periodogram analysis of three sets each of 30 years 19561985) and one set of 25 years summer monsoon rainfall time series for 29 meteorological subdivisions in the Indian region. The important results of the present study are as follows. (i) The power spectrum of the temporal fluctuations of rainfall follows the universal inverse power law form of the statistical normal distribution, with the square of the eddy amplitude representing the eddy probability density corresponding to the normalized standard deviation t equal to (log I/log &) -1; where 1 is the period length in years and I,, the period up to which the cumulative percentage contribution to total variance is equal to 50 and t = O .(ii) Periodicities in rainfall up to 3-4 years contribute to as much as 50 per cent of the total variance.A universal spectrum for interannual variability in summer monsoon rainfall indicates predictability of the overall pattern of rainfall fluctuations. A relatively recent and short period rainfall time series, such as the 30-year period 19561985 in this study, enables identification of the universal structure of atmospheric variability. Further, short period fluctuations that are major contributors to interannual variability can be identified accurately in the 30-year data sets and provide means for estimating the near future (up to 4 years) rainfall variation. KEY WORDS Self-organized criticality Deterministic chaos Universal spectrum for rainfall variability Interannual variability of rainfall

Annual and seasonal mean global surface pressure time series for the 25 years 1964–1988 obtained from the Comprehensive Ocean Atmosphere Data Set (COADS) were subjected to quasi‐continuous periodogram spectral analysis. Periodogram estimates are summarized in the following: (i) the atmospheric interannual variability exhibits a broadband (eddy continuum) structure; (ii) the spectra follow the universal inverse power‐law form of the statistical normal distribution; (ii) periodicities up to 5 years contribute to as much as 50 per cent of the total variance; (v) the high‐ and low‐frequency El Niño–Southern Oscillation (ENSO) cycles of respective periodicities 3–4 years and 4–8 years and interdecadal oscillations are present in all the data sets. The inverse power‐law form for power spectra is ubiquitous to real‐world dynamical systems and is identified as a signature of self‐organized criticality or deterministic chaos. The above results are consistent with a recently developed cell dynamical system model for atmospheric flows, which predicts self‐organized criticali ty as intrinsic to quantum‐like mechanics governing atmospheric flow dynamics. Identification of self‐organized criticality in annual and seasonal mean surface pressure fluctuations and its unique quantification implies predictability of the total pattern of fluctuations. A universal spectrum for interannual variability rules out linear trends in atmospheric surface pressure patterns.

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Annual and seasonal mean global surface pressure time series for the 25 years 1964-1988 obtained from the Comprehensive Ocean Atmosphere Data Set (COADS) were subjected to quasi-continuous periodogram spectral analysis. Periodogram estimates are summarized in the following: (i) the atmospheric interannual variability exhibits a broadband (eddy continuum) structure; (ii) the spectra follow the universal inverse power-law form of the statistical normal distribution; (ii) periodicities up to 5 years contribute to as much as 50 per cent of the total variance; (v) the high-and low-frequency El Niiio-Southern Oscillation (ENSO) cycles of respective periodicities 3-4 years and 4-8 years and interdecadal oscillations are present in all the data sets.The inverse power-law form for power spectra is ubiquitous to real-world dynamical systems and is identified as a signature of self-organized criticality or deterministic chaos.The above results are consistent with a recently developed cell dynamical system model for atmospheric flows, which predicts self-organized criticality as intrinsic to quantum-like mechanics governing atmospheric flow dynamics. Identification of selforganized criticality in annual and seasonal mean surface pressure fluctuations and its unique quantification implies predictability of the total pattern of fluctuations. A universal spectrum for interannual variability rules out linear trends in atmospheric surface pressure patterns.