Finally, we look at tides as another source of high-frequency variability in the ADCP data.  For the WAP region, the strongest predicted tidal currents are diurnal topographic vorticity waves along the shelf break. Part of our task is to improve the tidal models of this region, but we need the revised bathymetry and data from the moorings before we can do this.

This plot shows the RMS diurnal-band velocity for WHOI surface drifter #4.  Dick Limeburner provided these data.  The left hand panel codes this value by size of the dot, and gives a value once per day.  It only shows points where there are enough ARGOS position data to do a good fit. The upper right panel shows U and V components for the buoy motion.  You can see that peak currents are about 15 cm/s.  The lower right panel shows water depth under the buoy track, interpolated from our tide model grid (CATS01.02).

The main point of this figure is to show that there are strong currents associated with tides in some regions.  So, if we want to use the ADCP data to look at mean circulation over the WAP region, we need to think about possibly large signals from near-inertial oscillations and tides.