Wave hindcast studies using SWAN nested in WAVEWATCH III - comparison with measured nearshore buoy data off Karwar, eastern Arabian Sea

Abstract

Waves in the nearshore waters (~15 m water-depth) of eastern Arabian Sea were simulated using SWAN nested in WAVEWATCH III (WW3) for the year 2014. The sensitivity of the numerical wave model WW3 towards different source term (ST) packages was tested. The performance of WW3 was evaluated with the measured deep water buoy data at 15.0000° N, 69.0000° E. Overall, the WW3 wave hindcast results using ST4 physics in deep water show a reasonable match (r=0.97 and SI=0.16) with the measured significant wave height (H_s). In deep water, a large overestimation (~23.7%) of mean wave period was observed using ST2 compared to ~8.2% using ST4. Komen et al. (1984) whitecapping formulation was found suitable based on the sensitivity studies of SWAN. Simulated Hs using nested SWAN model shows good correlation (r=0.96) with the nearshore measured data. During high sea state (H_s>2 m), an overestimation (~19.8% for ST2 and ~21.4% for ST4) and during low sea state (H_s<1 m), an underestimation (~16.1% for ST2 and ~31.5% for ST4) in mean wave period was observed in the nearshore. WW3 model forced by modified wind field (speed increased by 5%) during June and July resulted in a reduction in underestimation of Hs from 8.6% to 2.2%.