Wind, current, and wave data for portions of the release period are 
shown in Figure 7, The average current velocity, Uv, integrated along the 
axis of the dye plume, was 0.30 m/sec (0.54 kn) during the period of moni- 
toring (1130 - 1230 hours) upon which the results below are based. 
Neighbor diffusivity, F (2) was calculated from returns of drift 
bottles. FE (4) had a minimum value of 316 cm2/sec and the coefficient e . 
in F (2) = ef£ /3 had the minimum value 0.062. This last value was calcu- 
lated using Stommel's (1949) expression, 
Gein?) . (Gn = ie 
Ree Nan Care| ene aL eee an OT Pano 
for the reduction of the experimental observations, where £ is initial 
neighbor separation (cm), £1; is separation after time T (sec), and the 
bars denote averages. The minimum value of ¢ falls within the range of 
values (0.006 - 0.08) that have been determined (cf. Pearson, 1956, Table 
10; Harrison, 1963, Table 1) for other oceanic areas subject to tidal cur- 
rents of variable strength. A calculation that allows for the turning of 
the drifters as they enter the longshore current system shows that a maxi- 
mum value for e€ would not exceed 0.075. 
Additional diffusion values were calculated from measurement of dye 
concentration along the axis of the steady state plume (Figure 7). A 
log-log plot (Figure 8) of a "concentration ratio", c-M -.D versus x, for 
values of x between 800 and 3800 meters, fits an xl relationship where c 
equals peak dye concentration, M equals rate of dye discharge (g/sec), D 
equals layer depth (meters) and x equals distance in meters along the axis 
of the plume. Thus, there was a decrease in dye concentration downstream 
from the discharge point proportional to the minus one power of the 
distance. 
Calculation of the so-called "diffusion velocity" yielded a value of 
2x 1073 m/sec. This value was computed from a relationship proposed by 
Schonfeld (1959) and expressed by Okubo (1962) as: 
m/U w x/U 
ur GYfty? © ye 
where S (x,y) equals the mean concentration at some point (x,y) in the 
plume, x being in the direction along the axis of the plume and y the 
direction perpendicular to the axis of the plume, m equals the number 
of particles released per unit time, U equals the mean flow, and W equals 
the "diffusion velocity". When solving for w, S (x) is expressed as the 
concentration ratio (mentioned above), in order to correct for depth- 
dependent variations in dye concentration along the axis of the plume, 
The approximate value for diffusion velocity(2 x 10-3m/sec) found in this 
