17 APRIL 194 
800 1600 
(8 APRIL 
0000 0000 
| 
i945 
1600 
19 APRIL 1945 
0000 2000 
~ OBSERVED AND COMPUTED 
WAVE PERIODS 
LEGEND 
OBSERVED PERIOD 
AT PENDEEN, OUTER BAND 
OBSERVED PERIOD | 
ArT PENDEEN, INNER BAND i 
} 
COMPUTED PERIOD AT PENOEEN, Ty 
COMPUTED TRAVEL TIME, ty 
COMPUTED PERIOD 
AT END OF FETCH, 1, 
WAVE PERIOO IN SECONDS 
OBSERVED AND COMPUTED 
WAVE HEIGHTS 
LEGEND 
— —— OBSERVED WAVE HEIGHT AT PENDEEN, UNSMOOTHED 
—— OBSERVED WAVE HEIGHT AT PENDEEN, SMOOTHED 
COMPUTED WAVE HEIGHT AT PENOEEN, SMOOTHED 
45 —— COMPUTED TRAVEL TIME, to 
O —~ COMPUTED WAVE HEIGHT AT PENDEEN, INDIVIDUAL 
POINTS 
f 
T 
| 
| 
COMPUTED WAVE HEIGHT IN FEES 
ABVULIBYY ‘LHOI3H G3AVM C3AHISEO 
312s 
° 
e000 0000 800 
17 APRIL 1945 
1690 
1B APRIL 1945, 
° 
2400 
1600 
1945 
0000 
19 APRIL 
Figure 15.—Observed and computed wave periods and wave heights at Pendeen, England, April 17 to 19, 
1945. For explanation see text. 
spondingly greater velocity of progress and greater 
length. He quotes (1911, p. 94) one particular 
instance in the Atlantic Ocean when swell from 
one source was observed by a number of vessels 
which reported longer and longer periods the 
greater their distance from the source. At a 
distance of 6,700 km. from the source the period 
had increased by a factor of 1.7. Kriimmel there- 
fore concluded that the waves increase in period, 
velocity of progress, and length as they move away 
from their source. 
34 
This conclusion is substantiated by an cxamina- 
tion of the frequencies of different wind velocities 
over the North Pacific and the North Atlantic 
and of the frequencies of swell of different periods 
on the coasts of southern California and of north- 
west Africa. Table 5 shows the periods of waves 
produced by different wind velocities and wind 
durations. The wave heights and periods for 
wind durations of 20, 30, and 40 hours, are taken 
from the curves in figure 7 which are based upon 
theoretical considerations but which have been 
