Internal Waves 



549 



Table 96. Records of Internal Tide Waves 



Kattegat 6-21 November 1932 (According to Kullcnberg) 



siderably greater than at the second one, but the phases are identical. For 

 the tide S 2 the amplitudes are smaller, the phase difference is over 2 h. This 

 is not very significant, considering the difficulty in determining S 2 . These 

 and other results mean that the internal wave was probably of the progressive 

 Kelvin type, travelling in a direction normal to the line connecting the two 

 stations (direction of this line from 60° to 240°). From the data of other 

 stations the wave velocity was found to be 89 cm/sec. This agrees with the 

 value of 93 cm/sec, which was computed from the density distribution and 

 the thickness of the layers (equation XVI. 17). 



8 



•4:XI 



Fig. 229. 



16 



16 





 18: XI 



16 



8 

 I9=XI 



8 16 8 16 8 



I5=XI I6:XI I7--XI 



Records of the recording boundary gauge from Station VII in the Kattegat, 

 14-19 November 1932 (Kullenberg). 



The recordings show in a remarkable way variations of the amplitude with 

 the character of beats (see Fig. 229 as an example). Kullenberg proved with 

 a Schuster periodogram that in addition to the ordinary tidal periods there 

 is a wave with a period of 14 5 h which corresponds to the period of the 

 inertia oscillation of 12 pendulum hours. This follows from the fact that 

 the period of beat is slightly over 3 days, which agrees with the period re- 

 sulting from the superposition of a wave of 12-3 and one of 14-5 h.* But 



* In the case of equal amplitude for both waves 



2ji 2ti Tji 2ti 



acos /+ o cos / = 2acos / • cos / . 



12-3 14-5 162-1 13-1 



The period of beat is consequently 81-06 h = 3 days, 9 h. 



