Principal axes for both the hour-averaged and low-passed currents were computed for the entire record and by month. Major and minor axes, orientation, and ellipticity were computed from the east (u) and north (v) current components as:

major axis = [0.5 (UU + VV) + R] / n}^(1/2)
minor axis = [0 5 (UU + VV) - R] / n}^(1/2)
orientation = 90° - 0.5 tan-1 [2 UV / (UU - VV)]
ellipticity = 1 - (minor axis / major axis)

where

UV = Sum(u*v) - n*U*V

UU = Sum(u*u) - n*U*U
VV= Sum(v*v) - n*V*V
R = [ (0.5 (UU - VV) )² + (UV)² ]^(1/2)

and U and V are the means of the east and north velocity components, respectively. Sum means sum over the entire data set of n valves. The orientation is measured clockwise from true north. 0° is true north, and 90° is east.

Principal Axes for Entire Record (ADCP/MAVS/BASS Observations)

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Principal Axes for Each Station