Sea and swell characteristics in the deep waters of the Northern and Southern Arabian Sea

Abstract

The main aim of this paper is to study the characteristics of sea and swell waves in the Arabian Sea using deep sea moored buoys. This study examines wave measurements from the northern and southern Arabian Sea with a focus on spectral characteristics and seasonal variations over eight years. The analysis reveals a bimodal wave spectrum in January and February, with prominent wind-induced waves. In March, swells start to dominate, leading to a decrease in wind-driven waves. During the Southwest monsoon from June to September, swells subsequently become the dominant wave component, resulting in a single-peaked spectrum. Findings indicate that higher wave heights and extended periods are more frequent in the northern Arabian Sea (NAS), with considerable intra-annual variation in peak spectral energy during the monsoon season. The monthly averaged spectra revealed interannual variability during the SW monsoon, with peak spectral energy of swell waves decreasing in June, July and increasing in August. The seasonal patterns exhibited significant changes over the years, with opposing trends in Hm0 values between July and August for the northern and southern parts of the Arabian Sea. Directional spectra derived from the in-situ data during the two concurrent cyclones, Tropical Cyclone Kyarr and Tropical Cyclone Maha, were analysed, where maximum significant wave heights (Hm0) of 7.38 and 3.29 m were observed. Model-derived wave parameters are compared with measured data, revealing a clear underestimation and overestimation of the significant wave heights during extreme events by the ERA5 model.