3.4 Progressive Vector Diagram 
The 1-hour averaged east (X) and north (Y) displacements (in 
kilometers) were given by Xm = Um* 36°1073 and Y, = Vi, * 361073, The 
progressive vector diagram (Sverdrup et al., 1942), which represents the 
path taken by a water particle if it is assumed that the observed motion 
is characteristic of a considerably extended water mass, was generated 
by successive additions of the end points of the position vectors 
(ean Vay) The progressive vector diagram, which accentuates very low 
frequency events (e.g., mean flow), is not the horizontal projection of 
a water particle trajectory with time. The spatial scale of the diagram 
corresponds to the displacement which would occur if the motion over the 
entire area (i.e., the extent of the displacement diagram) were the same 
as that observed at the location of the current meter. 
The plot begins with an asterisk surrounded by a circle. Every 
twelfth hour is marked on the curve by an asterisk. 
3.5 East and North Periodograms 
By use of a fast Fourier transform algorithm, raw periodograms 
(Bingham et al.,1967), defined so that the integral over positive fre- 
quencies is equal to twice the total variance, were computed for the 
l-hour vector averaged U, and V,, series. (We note that generally a 
periodogram ordinate is not a consistent spectral estimate of a random 
process.) The data length (90 hours) was too short to form spectral 
estimates. 
