Modeling and Analysis of the Wind-Waves Field Variability in the Indian Ocean During 1998-2009 Years

TL;DR

This study models and analyzes the variability of wind-generated waves in the Indian Ocean from 1998 to 2009 using a modified WAM model, revealing a positive trend in wave height and energy over 12 years.

Contribution

The paper introduces a modified WAM model with improved accuracy for Indian Ocean wave simulations and provides a comprehensive analysis of wave variability and trends over 12 years.

Findings

Wave height and energy show a positive 12-year trend (~1% and 2% per year).

The modified WAM model improves accuracy by 35% over the original.

Statistical analysis reveals the distribution and variability features of the wave field.

Abstract

To calculate the wind-waves in the Indian Ocean (IO), the wind field for the period from 1998 to 2009 was used, obtained from the NCEP/NOAA archive, and numerical model WAM (Cycle-4) was applied, modified by the new source function proposed in Polnikov (2005). Based on buoy data for the Indian Ocean, the fitting of the modified model WAM was done, which provides the win in accuracy of calculations on 35%, in comparison with the original model. All the further calculations of the wave fields in IO were made for these model settings. At the first stage, the analysis of the simulation results involves a) mapping the fields of the significant wave height <Hs(x,y,T,R)> and the wave energy <Ea(x,y,T,R>, calculated with different scales of averaging in time T and space R; b) estimating the fields of seasonal, annual and long-term variability; and c) determining the 12-year trend of the annually averaged fields. The analysis was carried out taking into account the previously introduced zoning the ocean area, provided by the spatial inhomogeneity of the wind field [3]. Further analysis includes a) creation of time series for the averaged (over zones and across the ocean) wave height, <Hs(x,y,T,R)>, and wave energy, <Ea(x,y,T,R>; b) construction of the frequency spectra of these series; c) finding the extrema of wave field; d) making histograms of wave heights (in the zones and the whole ocean); and e) calculating the first four statistical moments for the waveheight field (in the zones and whole IO). The results obtained allow us to estimate the stored energy of the wave field in the Indian Ocean and the scales of its variability; to establish a positive 12-year trend of the averaged wave height (about 1% per year) and wave energy (2% per year); to determine features of the probability distribution; and to describe the statistical properties of the wave field in the zones of the Indian ocean.