Spectral characteristics of Surface Fields in the Regional Domains of the Indian Ocean and interannual Monsoon Variability

摘要

Spectral analysis and variance have been employed on sea surface temperature (SST), mean sea level pressure, zonal and meridional wind stress, latent and sensible heat fluxes for four regional domains in the Indian Ocean. The data for the present study consists of the uninitialised European Centre for Medium Range Weather Forecasts (ECMWF) model analyses (0 UTC) from 1985 to 1990. Power spectra show that latent and sensible heat fluxes have predominant oscillations in the semiannual band while in the rest of the surface fields the oscillations are dominant in the annual band. Composite time series and power spectra do not depict well the contrast between below normal and normal/above normal monsoon. But the composite variance spectra reflect the contrasting features very well Difference in coherence and phase propagation of surface fields, especially in the seasonal band, between normal/above normal and below normal monsoon years are apparent from the cross spectrum analysis and indicative of the significant role of phase propagation in the seasonal band in interannual monsoon variability.