OCEAN WAVES AS A METEOROLOGICAL TOOL 
mination of wave height. In the determination of wave 
height the response characteristics of the instrument 
enter as an important factor, and it may be necessary 
to take into account, by means of specially constructed 
“refraction diagrams” [7, 12], the effect of bottom 
topography and of the configuration of the coastlines. 
Wave periods, on the other hand, are relatively easy to 
ascertain from wave records and are not subject to the 
complex changes in wave pattern that occur as waves 
come into shallow water. Determination of wave di- 
rection by means of a Rayleigh disk or a two-unit wave 
station are being investigated. 
It is not likely that the SS method will make it pos- 
sible to compute the storm distance from records at a 
single station. The distance determination for the FA 
method depends upon the high dispersiveness of ocean 
swell, and storm surges are almost nondispersive. In 
view of the great length of storm surges they will also 
be subject to considerable refraction. The principal 
hope lies in the determination of the arrival time of 
identical phases at two or three stations, and the loca- 
tion of storms from special charts based on the propaga- 
tion at »/gh velocity. 
Range. It is estimated that the HT method can be 
used to distances up to 3000 nautical miles, the FA 
method to distances exceeding 3000 miles. The range 
of the SS method is not known. The values given above 
are in excess of those that have been obtained by seis- 
mic and electromagnetic methods. 
Group Velocity. The group velocities applicable for 
the HT, FA, and SS methods are of the order of 400, 
900, and 10,000 nautical miles per day respectively. The 
relatively long interval between the time the waves are 
generated and the time they are recorded at the wave 
station is a disadvantage in the application of the HT 
and FA methods. Their practical use will, therefore, be 
largely to verify or modify the interpretation already 
made on the basis of meteorological information. In the 
case of compact meteorological disturbances, such as 
young hurricanes, these waves may well provide the 
first clue as to the existence of the storms. The methods 
should be particularly useful over the southern oceans 
[3] and for other regions where the network of observ- 
ing stations is widely spaced. The group velocity of the 
storm surges, although slow compared to the seismic 
and electromagnetic waves, is sufficiently large to per- 
mit synoptic application. 
Storm Intensity. The HT method gives an estimate 
of the storm intensity. In the case of the FA method 
an estimate of wind speeds from the maximum re- 
corded period is suggested by Fig. 14. It is also hoped 
that studies dealing with the propagation of energy by 
the forerunners will lead to an interpretation of the 
spectrogram ordinate, which has received no attention 
so far but must be related to the storm intensity. The 
relationship between storm intensity and storm surges 
has not been studied. 
Other Storm Characteristics. The application of the 
methods employing ocean surface waves is further en- 
hanced by the possibility of determining not only the 
location and intensity of the storm, but also its size, 
1099 
type, acceleration, and other characteristics. In view 
of the close ‘‘coupling” between the wind pattern and 
the sea surface waves one might expect a better chance 
for success by the methods described in this report than 
by those based on seismic and electromagnetic waves.® 
Desirable Future Studies. With regard to the HT 
method the research requirements coincide with those 
pertaining to the problem of forecasting ocean waves 
and are discussed in another paper.’ Of particular im- 
portance is a better understanding of the decay of swell 
traveling through an area of calm or cross winds. In 
this connection it is planned to establish a wave re- 
corder in the equatorial Pacific, possibly on the Mar- 
quesas Islands. These islands lie 2400 miles and about 
6 days ‘“‘up-swell” from California, and a comparison 
of wave records obtaimed there with those at Ocean- 
side, California, would give information concerning the 
attenuation of swell over large distances. It is hoped 
that these studies may help to bring about, on a scien- 
tific basis, a revival of the ancient art of judging weather 
from the appearance of the sea surface. 
The FA method appears to have reached a stage of 
development where it will be possible to work with 
records from a network of stations, rather than from a 
single station. We may expect marked progress as a 
consequence. Our present experience is almost en- 
tirely confined to stations in the eastern Atlantic toward 
which the storms weremoving.® Development and stand- 
ardization of suitable recording and analyzing equip- 
ment is urgently needed. The determination of wave 
direction is an essential requirement in making use of 
wave records for tracking storms. 
The SS method is at such an early stage of develop- 
ment that further work along instrumental and theo- 
retical lines is required before it is possible to make any 
definite recommendations. An improved instrument has 
been installed at the end of the Scripps Institution Pier, 
in La Jolla, California, and similar units will be in- 
stalled during 1950 at Oceanside, California, 30 miles 
north of La Jolla (for direction determination) and in 
Hawaii. By means of this network of long-period-wave 
stations it is hoped that research on the generation and 
propagation of storm ‘surges can be vigorously pushed. 
In conclusion it must be emphasized that it would be 
most unfortunate if study were to be limited to the 
three methods with which we have been chiefly con- 
cerned here. A systematic exploration of the spectrum 
of ocean waves is likely to lead to surprising new de- 
velopments. In this connection it should be remembered 
that the sea surface wave pattern provides a complete 
picture, though a distorted one, of the entire wind dis- 
tribution over the ocean, and our interpretation of this 
8. Recent evidence [3] indicates that some of the micro- 
seismic activity is caused by the interference pattern of the 
surface waves in the storm area. Apparently a second-order 
effect inherent in such a pattern is associated with pressure 
fluctuations which do not disappear at great depth. 
9. Lt. R. L. Miller, USAF, has successfully applied the 
method to a storm over the Bering Sea, using wave records 
taken at Guam, located to the rear of the moving storm 
(Scripps Institution Wave Report No. 90, unpublished). 
