Spectral characteristics of surface fields in the Indian seas and inter-annual monsoon variability

Abstract

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 of four regional domains in the Indian Ocean. The data for the present study consist of the uninitialized European Center for Medium Range Weather Forecasts (ECMWF) model analyses (00 UTC) from 1985 to 1990. Composite time series and power spectra do not depict well the contrast between below normal and normal/above normal monsoons. But the composite variance spectra reflect the contrasting features very well. Differences 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 these indicate the significant role of phase propagation in the seasonal and inter-annual monsoon variability.