Spectra of long‐term series for wind speed and wave height in the Indian Ocean area

Abstract

AbstractThe spectra of long‐term series of wind velocity and significant wave height were built in two domains of variability scales: from 1 day to 1 year (D1) and from 1 year to 15 years (D2). Surface wind data from the ERA‐Interim reanalysis in the Indian Ocean area for the period of 1979–2015 years, and wave heights simulated with the improved WAM model, were used for this purpose. In order to study the spatial variability of the spectral shapes, spectra of wind speed and wave height were calculated at two sections located along the meridians and three sections located along latitudes with a step of 3°. For the D1 domain, the existence of three ranges of variability scales (R1, R2, and R3) are shown in which both types of spectra have the well‐defined and visibly different power‐like slopes varying in dependence on the offset from the equator. The Navier‐Stokes equations were analyzed in order to design a theoretical interpretation of the spectral shapes features found in the D1 domain. For the D2 domain, no unified system of isolated frequencies has been revealed, which is expected for the entire Indian Ocean. Among the set of selected periods, the most stable one is the variability period of around 5.5 years. Results presented in this work are discussed.