Breaking Waves in the Gulf of Tehuantepec

We present observations of ocean surface breaking wave variation with wind speed and fetch. Breaking waves play an important role in air-sea interaction: enhancing momentum flux from the atmosphere to the ocean; dissipating wave energy that is then available for turbulent mixing; injecting aerosols and sea spray into the air, and entraining air in the water. A better understanding of wave breaking kinematics and dynamics is important for wave modeling, remote sensing in the microwave and visible wavelengths, and furthering our understanding of surface waves. Surface wave and atmospheric boundary layer data were collected during the Gulf of Tehuantepec experiment (GOTEX) off the Pacific coast of Southern Mexico in February 2004. A nadir-looking mega-pixel video camera, along with a scanning lidar, laser altimeter, and inertial measurement unit, was mounted onboard the NCAR C-130Q Hercules aircraft. The imaging and scanning system recorded digital videos of the breaking sea surface and corresponding surface wave heights during strong (10-25m/s), steady off-shore winds over fetches from 0 to 500km. Boundary layer wind profiles were measured using GPS dropsondes and a pressure transducer array on the aircraft radome. Whitecaps are identified in the images using brightness thresholding, the image brightness gradient, and the brightness cumulative probability function. The observed dependence of whitecapping on fetch and surface wind speed is presented.