Despite these continuing theoretical efforts, however. 

 It Is only very recently that field experiments have suc- 

 ceeded In Identifying some of the principal features of the 

 overall energy balance of the wave spectrum. Earlier field 

 studies by Snyder and Cox (1966) and Barnett and Wllkerson 

 (1967) revealed that Phillips' and Miles' mechanisms were 

 too weak by almost an order of magnitude to explain the 

 observed wave growth rates. On the basis of a series of 

 wave growth measurements In Hakata Bay and a wind-wave tank, 

 Mltsuyasu ([36a, b] [37] [ 38]) concluded later that the evo- 

 lution of the spectrum was strongly Influenced by wave-wave 

 Interactions as well as the energy transferred from the 

 wind. Extensive large-scale measurements of spectral growth 

 during the Joint North Sea Wave Project (JONSWAP, [5]) have 

 recently confirmed Mltsuyasu's Interpretation quantitatively; 

 the characteristic, sharply peaked form of developing wave 

 spectra and the associated rapid growth rates on the forward 

 face of the spectrum could be explained as a self-stablllzlng 

 feature of the nonlinear wave Interactions. Indirectly, the 

 measurements also yielded an estimate of the energy and 

 momentum transferred from the wind to the waves. The dis- 

 cussion of the energy balance of wind-wave spectra In the 

 first part of this review will accordingly be based primar- 

 ily on the picture that has evolved from the analysis of 

 the JONSWAP data. 



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