M. K. Kulkarni

SIGNATURES OF A UNIVERSAL SPECTRUM FOR ATMOSPHERIC INTERANNUAL VARIABILITY IN COADS SURFACE PRESSURE TIME SERIES

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. Periodograrn 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 highand low-frequency El Niii-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 abnospheric flows, which predicts self-organized criticality as intrinsic to quantum-like mechanics governing abnospheric 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 spectnun for interannual variability rules out linear trends in atmospheric surface pressure patterns.

Some unique characteristics of atmospheric interannual variability in rainfall time series over India and the United Kingdom

Continuous periodogram analyses of two 50-years (1871–1920 and 1936–1985) of summer monsoon rainfall over the Indian region and one 84-years set (1893–1976) of winter half-year rainfall over England and Wales show that the power spectra of disparate rainfall regimes follow the universal and unique inverse power law form of the statistical normal distribution with the percentage contribution to total variance representating the eddy probability corresponding to the normalized standard deviation equal to [(log L/logT50)−1] whereL is the period in years andT50 the period up to which the cumulative percentage contribution to total variance is equal to 50. The above results are consistent with a recently developed non-deterministic cell dynamical system model for atmospheric flows. The implications of the above results for prediction of interannual variability of rainfall is discussed.