The horizontal coherence of inertial oscillations in a coastal region

The horizontal coherence of inertial oscillations was investigated using the records from six current meters moored on the Oregon continental shelf and whose separation distance varied from approximately 9 to 35 km. The rotary component method for analyzing vector time series was used to form the cross spectra and coherencies for 15 pairs of records, the length of which varied from 10 to 27 days. The velocity field was found to be highly coherent for periods greater than about 10 days. The coherencies at the inertial frequency, which were generally quite low, could be accounted for (with some exceptions) by a consideration of both the separation distance and a simple representation of the effects of stratification.