Scatter Plots

Scatter plots of the one minute and low-passed currents (calculated from hourly averaged data and subsampled by 6) visually show the distribution of the current speed and direction. Superimposed on the scatter plots are the mean vector current over the entire deployment (red arrow), and the principal axes of the currents (red ellipse centered at end of mean vector).

Principal axes of the currents were computed for the entire data record (using data at the basic sampling interval). Major (Maj) and minor (Min) axes, orientation (OR), and ellipticity (EL) 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 (in cm/s), respectively. The orientation (OR) is measured clockwise from true north. 0° is true north, and 90° is east. The depth is measured in meters below the surface, and the sampling interval (SI) is in minutes. EL is ellipticity.

Table in Excel Format

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