TM No. 377 

 CHAPTER IV 

 FIELD OBSERVATIONS 



This chapter presents a discussion of the various wave observations, 

 emphasizing the equipment and techniques utilized. Preliminary wave mea- 

 surements made from a Navy pier in Narragansett Bay are briefly summarized. 

 The remainder of the chapter is devoted to the various observations made 

 from the Buzzards Bay Entrance Light Station,, 



In reporting these experiments, an effort is made to describe precisely 

 the method of using the wave meters, paying careful attention to the manner 

 of instrument suspension in the ocean. A knowledge of the methods used to 

 make the observations is important, since the assessment of the instrument 

 response to wave motions presents obvious difficulties,, The calibration 

 procedures described in chapter II involved no measurements of real ocean 

 waves along with simultaneous observations employing an independent method. 

 Hence , it was necessary to depend, to a certain extent, upon the results 

 of the field measurements to evaluate the wave meters. 



The field observations made from the Buzzards Bay Entrance Light Station 

 (for brevity called BBELS) may be divided into three catagori.es „ First are 

 the primary wave measurements using the various wave meter systems (OMDUM II 

 and III, and LIMDUM l) discussed in chapter II. The second type are those 

 observations that provide direct supplementary information regarding the 

 meteorological 1 , and oceanographies! conditions (wind velocity and estimates 

 of sea and swell) at the time of the wave meas;ireinentSo The third catagory 

 is associated with relatively long term complementary observations of the 

 oceanographic "climate" around the BBELS. 



Since it is one aim of this report to explore and, if possible, to 

 demonstrate both the feasibility and value of making oceanographic obser- 

 vations from ocean tower facilities such as BBELS, the pertinent features 

 of the BBELS facility are described. Information is also presented regarding 

 the general characteristics of the wind and wave conditions and of the regional 

 geography. A discussion of the current and free surface tide level variations 

 is based on actual observations made. In malting tidal current measurements, 

 information was also obtained regarding short term horizontal current fluctu- 

 ations. This information was important in assessing the observed wave motions. 



The presentation of the wave data posed some difficulty because of its 

 quantity. The voluminous results were therefore condensed and summarized 

 (see table IV=3 at the end of this chapter). Computer listings of the statis- 

 tical data and plots of the auto-spectra are presented in appendix B. The 

 data are discussed in chapter V. 



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