Observations of Wind Effects on Shoaling Wave Shape

Surfers know that the wind direction (onshore vs. offshore) plays an important role in the surfing quality of the waves. A previous laboratory investigation noted that onshore wind tends to lead to spilling waves that break farther offshore than without wind and offshore wind tends to lead to plunging wave that break closer to shore. An additional investigation noted that the non-dimensional onshore wind speed affected the shoaling wave shape (skewness and asymmetry), but did not include offshore wind. These controlled laboratory experiments used small waves. Field scale ocean measurements are challenging due the non-stationarity of the wind, wave field, and underlying bathymetry. Here, we present detailed observations of wave shape for steady field-scale waves (~2 m breaking waves) on a fixed bathymetry with naturally variable wind at the WSL wave company facility in Lemoore CA. Wave were observed wave staffs and six lidars focussed on detailed region of wave shoaling and breaking. One lidar was mounted on a drone and another 32-beam Velodyne lidar was mounted on pole looking down at the breakpoint. During measurements, the wind varied substantially from 10 m/s out of the NW and 3 m/s out of the South. Funded by the Mark Walk Wolfinger Surfzone Processes Research Fund.