Climatology of wave period in the Arabian Sea and its variability during the recent 40 years

Abstract

Information on wave period is required for designing marine facilities. Characteristics of peak period (Tp) can reveal swell or wind-sea predominance at a location. Mean wave period (Tm) and Tp from reanalysis data spanning 40 years in the Arabian Sea (AS) were examined. The mean annual and interannual variabilities and trends in Tp were also examined. Spatial variation in Tp was 12% and high-frequency waves were relatively more in the northern AS. Presence of swells was more in eastern AS than in western AS. Tm during the monsoon months was higher than that during non-monsoon months. Inter-annual variations in the annual Tm were 8-18%, whereas that in Tp was 11-21%. In most eastern AS regions, climatological monthly Tp was largest in April-May and smallest in January. Heights of the intermediate-period waves were higher. A decreasing trend in Tp was found, with values between 0.1 and 0.3 s/decade. Linkages to El Ni�o Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and Southern Annular Mode (SAM) on Tp in the AS basin were also examined. Results suggest that the ENSO events and IOD events modulate the eastern and the western AS Tp anomalies and SAM is negatively correlated with Tp anomalies in the AS.