1092 
Most of the older instruments recorded the elevation of 
the sea surface against time by some suitable arrange- 
ments of floats. During World War II very effective 
methods were developed which derive from the under- 
water pressure fluctuations induced by the surface 
waves. It is curious that this mode of attack should 
have been initiated independently in Great Britain and 
the United States. An early model developed by the 
MARINE METEOROLOGY 
been developed at the College of Engineering, Uni- 
versity of California [6], and these have been installed 
at Quillayute River, Washington; Heceta Head, 
Oregon; Point Cabrillo, Point Sur, Point Arguello, 
Oceanside, and La Jolla, California; and on the island 
of Guam. 
Although the various instruments differ in many im- 
portant aspects, the following principles are common. to 
150° 140° 130° 120° 110° 
iy, Fa CY 
LP FREQUENT 
-& 
STAGNATION Ye 
HER a 
E q G 
STATIONARY 
PAGIFIC—HIGH 
(SUMMER ONLY)} 
CHARACTER OF 
E 
GOAST OF SOUTHERN SPRING ,oca, WAVES AT 
CALIFORNIA 
SAN? OCEAI & 
NICOLAS |. LA XMOL 
CLEMENTE ER 
WAVE HEIGHT,H, IN F 
PACIFIC HIGH 
INSET B 
COASTAL 
FRONTS 
GULF OF 
ALASKA 
HEMISPHERE 
WAVE PERIOD,T,IN SECONDS 
120° 130° 140° 150° 160° “170° 180° 
170° 160° 150° 140° 130° 120° 110° 
Fie. 3.—Origin of waves reaching La Jolla, California. The capital letters on the large chart represent typical meteorological 
situations, which give rise at La Jolla to waves of heights and periods shown in inset B. Inset A is a chart of the region near 
La Jolla on an enlarged scale. The shaded areas on the large chart represent typical fetches, that is, areas where the waves 
are generated. The isobaric pattern and the nature of the meteorological fronts are also indicated. The large open arrows 
represent typical paths of the storm systems. The wavy arrows indicate the direction of the waves leaving the storm systems. 
The figure cannot represent the nature of the meteorological situations with any degree of ‘accuracy, but it is supposed to il- 
lustrate how different meteorological situations can be identified by the height and period of the waves with which they are 
associated. (From Munk and Traylor [12].) 
Mine Design Department, British Admiralty, has been 
in operation at Pendeen, near Lands End, England, 
since 1944. In the United States the development of 
wave instruments has been carried out chiefly at the 
Woods Hole Oceanographic Institution and at the De- 
partment of Engineering of the University of California. 
In an early model designed by M. Ewing the recording 
apparatus was contained directly in the underwater 
unit. Later, units recording on shore were installed near 
Cuttyhunk, Massachusetts, and on the island of 
Bermuda [8]. A number of shore recording models have 
most wave instruments of the underwater pressure type 
and should be understood for a proper interpretation of 
the records. Surface waves induce pressure fluctuations 
in the entire column of water between the surface and 
the sea bottom (Fig. 4). For any given wave height and 
depth of water, the amplitude of these fluctuations de- 
pends on the wave period in such a manner that waves 
of very short period are virtually eliminated, The under- 
water unit measures the deviation of the fluctuating 
pressure at the sea bottom from the mean hydrostatic 
pressure. A “slow leak” in the underwater unit elimi- 
