CONTENTS 



Page 



PREFACE 1 



PART I: INTRODUCTION 4 



Basic Problem 4 



Conventional Approach 5 



Irregular Waves Versus Monochromatic Waves 6 



Models of Frequency Spectra 7 



Importance of Directionally Distributed Wave Energy 7 



Common Directional Wave Gages 10 



Gage Arrays 13 



Measurement Program 15 



PART II: NOTATION AND SEMANTICS OF DIRECTIONAL SPECTRA 18 



Review of Basic Definitions 18 



Some Fundamental Bulk Parameters 24 



Some Illustrated Examples 26 



PART III: MEASUREMENT SCHEME 31 



Measurement Site 31 



Physical Description of the Array 33 



Data Collection 36 



Error Checking 37 



Directional Spectral Estimation 41 



Working Data Base 45 



PART IV: EXAMPLES OF OBSERVED FREQUENCY- DIRECTION SPECTRA 47 



Low- Wind, Low- Energy Regime 47 



Early Storm Example 49 



A Well-Developed Sea State 51 



PART V: DATA REDUCTION/PARAMETERIZATION 54 



Frequency Characterization of Spread, Asymmetry, and Position ... 54 



Some Bulk Spreading Parameters 60 



Parameters for Modal Analysis 62 



Parameter Data Base 67 



PART VI: BULK DIRECTIONAL CHARACTERISTICS 70 



Peak Direction 70 



Directional Spread 76 



PART VII: MODAL ANALYSIS 83 



