Characteristics of long-period swells measured in the near shore regions of eastern Arabian Sea

• Ocean swells of period more than 18 s were observed along the eastern Arabian Sea.
• Long-period swells decrease towards the northern Arabian Sea.
• Wave spectra were with peak wave period at 18.2 s, secondary peak at ∼13.3 s and the wind-sea peak at ∼5 s.

Measured wave data covering two years simultaneously at 3 locations along the eastern Arabian Sea reveals the presence of long-period (peak wave period > 18 s) low-amplitude waves (significant wave height < 1 m) and the characteristics of these waves are described in this article. In a year, 1.4–3.6% of the time, the low-amplitude long-period swells were observed, and these waves were mainly during the non-monsoon period. The wave spectra during these long-period swells were multi-peaked with peak wave period around 18.2 s, the secondary peak period around 13.3 s and the wind-sea peak period at 5 s. The ratio of the spectral energy of the wind-sea peak and the primary peak (swell) was slightly higher at the northern location (0.2) than that at the southern location (0.15) due to the higher wind speed present at the northern location.