Morlet wavelet analysis of tropical convection over space and time: Study of poleward propagations of Intertropical Convergence Zone (ITCZ)

Abstract

A methodology to use continuous Morlet wavelet transform over space and time has been developed. By means of this method, the power spectra in 4‐dimensional space (viz. space, the spatial‐scale, time and the temporal‐scale) can been estimated. This is applied to study the spatial and temporal scales associated with the poleward propagations of the ITCZ (InterTropical Convergence Zone) over the Indian and West Pacific longitudes. The method has an added advantage that we can obtain the predominant spatial scales over a particular region, the temporal scales associated with them and their time of occurrence. We find that poleward propagations of ITCZ have a predominant spatial scale of about 30°. However the predominant temporal scale varies from year to year. Other regions which do not have significant poleward propagations do not show these (spatial and temporal) characteristics.