WIS Methods and Data 



41. In late 1976 a study to produce a wave climate for US coastal 

 waters was initiated at WES. This ongoing study, WIS, consists of three 

 phases. Phase I (Corson et al. 1981) and Phase II (Corson et al. 1982) wave 

 characteristics were generated by a numerical model which simultaneously 

 propagated and transformed the waves over a discrete grid representing seg- 

 ments of the Atlantic Ocean. Phase I acted in the deep ocean. Phase II acted 

 over the continental shelf where, for the purpose of classifying waves, depths 

 may be either intermediate or deep. Phase III draws upon the Phase II data to 

 provide nearshore wave characteristics in depths as shallow as 30 ft. For all 

 three phases, data are available at selected points referred to as stations. 



42. WIS methods and data were to be used to establish the boundary con- 

 ditions for ESCUBED. Theoretically, the ESCUBED grid could have been extended 

 seaward as far as the nearest Phase II station (Phase II stations are approxi- 

 mately 34 miles offshore and 34 miles apart), and the data available at this 

 station could then have been used in the boundary conditions. The costs of 

 computing over such a large grid would have been prohibitive. The Phase III 

 methodology provided an inexpensive bridge between the Phase II station and 

 the much smaller grid actually used. 



Phase III Methodology 



43. The reader is referred to Jensen (1983) for a complete description 

 of the Phase III methodology. A summary is given here. The Phase II results 

 comprise directional spectra. The Phase III methodology first takes these 

 spectra and separates them into two wave trains, swell and sea. The two are 

 assumed to behave independently. The swell is characterized by the height 



H , frequency f , and propagation direction 9 of a unidirectional, mono- 

 chromatic wave. The energy of the sea will be distributed in frequency- 

 direction space. A one-dimensional spectrum E«(f) can be defined in terms 

 of the directional or two-dimensional spectrum Ep(f,e) which is expressed as 



E (f) = J E (f,e) de (1) 



o 



40 



