A Numerical Model for the Calibration of CASP WOTAN Wind Data

We have developed a simple numerical model to calculate the effects of refraction in the water column on the noise signal detected by subsurface WOTAN (Wind Observation Through Ambient Noise) instruments. Recent continental shelf deployments of WOTANS, including those in CASP (Canadian Atlantic Storms Program) have resulted in noise-to-wind speed calibration relations which vary with the location of the instruments. This model was developed to investigate whether the sound speed profile above the WOTAN could account for the observed differences in wind speed calibration. The model uses a simple ray tracing scheme including spherical spreading and absorption to compute the sound intensity received at the WOTAN from a uniform array of dipole surface sources. Using sound speed profiles measured during CASP, the model predicts differences of up to 20% in the 4.3 kHz band noise among the five WOTAN stations.