Summertime surface diurnal period winds measured over an upwelling region near the Oregon coast

Wind measurements were made during July and August 1973 from surface floats installed 13 and 120 km from the Oregon coast. The striking feature of the kinetic energy spectra was the large peak at the diurnal frequency at the inshore site; at the offshore station the 24-hour peak was one fifth as large. At both sites the amplitude of the meridional or longshore component of the tidal wind was stronger than the zonal component by a factor of about 2, the shape of the hodograph was elliptical, and the velocity vector rotated in the clockwise direction. The horizontal coherence between the diurnal period winds was low, most likely because of the sharpness of the spectral peak. Mean daily variations of the eastward velocity component were consistent with local sea breeze circulation, and the sea breezelike pattern was superimposed upon the fairly steady northerly winds. With wind data obtained at five coastal stations, strong correspondence was found between the orientation and proximity of the coastal mountains and the ratio of the meridional to zonal components of the tidal wind. The diurnal period onshore winds may have been turned southward by the mountain barrier, causing the early morning increase in the northerly winds.