observations for an area will always be at approximately 

 the same phase in the S2 cycle, the harmonic constants 

 for So cannot be resolved. As a matter of fact, the S2 

 height at that time will be aliased into the mean height, 

 an undesirable consequence for both oceanographic and 

 geodetic purposes. 



Only a few years ago, it might have been considered 

 feasible to infer S2 harmonic constants from the other 

 large semidaily constituents using tidal equilibrium 

 theory and an assumption that since the oceans are not 

 finely tuned to particular frequencies, the response in 

 a narrow frequency band can be assumed to be smooth. 

 However, it has been demonstrated recently that there is 

 a significant meteorological S2 tide (called a radiational 

 time by Munk and Cartwright ) . This tide, which exists 

 only in a very narrow frequency band, is believed to be 

 caused by the solar semidaily barometric tide and by a 

 nonlinear contribution of wind stress associated with the 

 solar diurnal onshore-offshore winds. An equilibrium 

 inference of S2 would not include the meteorological 

 contribution at this frequency. 



The frequency of K]_, the largest diurnal constituent, 

 differs from that of S^ (solar diurnal, period 24 hours) 

 by one cycle per year. It is suggested in the literature 

 that this type of separation is not resolvable with data 



26-21 



