Dynamics of wave generation and dissipation processes during cold wave events in the Bohai Sea

Abstract

Wave dynamics were investigated by applying the wind-wave model Simulating Waves Nearshore to the semi-enclosed Bohai Sea during cold wave events. Wind quality was examined by comparing three wind data sources with buoy observations, and then numerical experiments were conducted to investigate the impacts of model physics settings on simulated waves. After model calibration, the wave dynamics were examined from the aspects of response to various wind conditions (speed, fetch, duration), wave dominant component (wind wave or swell), as well as the dissipation processes during a pair of cold wave events (e.g., northwesterly in 2014 and northeasterly in 2015) with the consideration of spatial differences. The maximum significant wave heights during two cold wave events are similar (e.g., 3.5 m in the central Bohai Basin), which attributes to the impacts of limited fetch difference and insufficient high wind duration. Wind wave is the dominant component, which is reflected in the wave spectra (e.g., wave age less than 1.2). Spatial regions of wave dissipations controlled by whitecapping, bottom friction, and depth-induced breaking during cold wave events are quantified. Whitecapping dominates the wave energy dissipation in deep-water areas, while the bottom friction dissipation controls the major dissipation process as waves propagate towards the coast (e.g., at 5–10 m water depths). Depth-induced dissipation only occurs over a narrow strip along the southern coastal area but is significantly beyond the others. Depth-induced dissipation decreases suddenly when reaches a flat bottom, and it decreases with the increase of the width of the bottom slope.