GUIDE WAVE ANALYSIS AND FORECASTING - WMO

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70 In addition to the spectral information, the WAVEOB code includes reports of derived wave parameters like significant wave height, spectral peak period, etc. The details of various sections of the WAVEOB code can be found in Annex II and in the WMO Manual on codes (WMO-No. 306, code form FM 65-IX; WMO, 1995). A binary format for reporting these data is also available, namely BUFR (code form FM 94-X Ext.). This code has been used experimentally for several years to transmit ERS-1 satellite data over the Global Telecommunication System. For reporting wave model forecast products in a gridded format, the approved code is called GRID (FM 47-IX Ext.) (see WMO-No. 306) in which the location of a grid point is reported first, followed by other information as defined above. A binary version, called GRIB, is now widely used. 6.4 Verification of wave models With ocean wave models being used in operational mode, appropriate verification of a wave model against observed wind and wave data is necessary and import- GUIDE TO WAVE ANALYSIS AND FORECASTING Figure 6.3 — A sample output (12-h forecast, valid 12 UTC, 13 September 1992) from the regional Gulf of Mexico shallowwater wave model operated by NOAA. The chart shows wave height values (in feet) and primary wave directions plotted at alternate grid points of the model (source: D. B. Rao, Marine Products Branch, NOAA) ant. The performance of a wave model must be continually assessed to determine its strengths and weaknesses so that it can be improved through adjustment or modifications. It is also necessary to develop sufficient confidence in the model products for operational use. There are a number of levels of model testing and verification. In wave model development a number of idealized test cases are usually modelled. The basic output of spectral wave models is the two-dimensional wave spectrum and a suitable test would be to use the model to simulate the evolution of a wave spectrum with fetch or duration for stationary uniform wind fields. Data from field experiments, such as the JONSWAP experiment (see Section 1.3.9), can be used to assess the model’s performance. Ideally, a model would be verified by comparisons with measured directional wave spectra. However, such measurements are relatively uncommon and there are problems with interpreting the results of comparisons of individual directional wave spectra. For example, in rapidly changing conditions, such as in storms, small errors in the prediction of the time of the storm peak can
OPERATIONAL WAVE MODELS 71 Figure 6.4 — A sample wave height chart from the wave model MRI-II operated by JMA. The chart shows contours of significant wave heights with thick solid lines for every 4 m, dashed lines for every metre and dotted lines for every half metre. Prevailing wind-wave directions are shown by arrows, while representative wave periods are shown by a small numeral attached to the arrow (source: Tadashi Asoh, JMA)
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WORLD METEOROLOGICAL ORGANIZATION G
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© 1998, World Meteorological Organ
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IV Chapter 7 - WAVES IN SHALLOW WAT
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ACKNOWLEDGEMENTS The revision of th
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VIII has been included particularly
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X considerable attention. Annex III
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2 η Crest Zero level a H = 2a a Tr
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4 Figure 1.5 — Paths of the water
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6 When waves propagate into shallow
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8 1.3.2 Wave groups and group veloc
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10 wavelengths in a given sea state
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12 for instance, a frequency of 0.1
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14 in which E(f) is the variance de
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16 2.1.1 Wind and pressure analyses
Page 29 and 30: 18 GUIDE TO WAVE ANALYSIS AND FOREC
Page 31 and 32: 20 Figure 2.2(a) (right) — Usual
Page 33 and 34: 22 As a quick approximation of ocea
Page 35 and 36: 24 GUIDE TO WAVE ANALYSIS AND FOREC
Page 37 and 38: 26 Gr G Gr ∇p C Cnf ∇p C Cnf
Page 39 and 40: 28 POINT C — The effect of warm a
Page 41 and 42: 30 a general sense, and can be appl
Page 43 and 44: 32 Free atmosphere Ekman layer Cons
Page 45 and 46: 3.1 Introduction This chapter gives
Page 47 and 48: ange of directions. Also, waves at
Page 49 and 50: small enough that swell can survive
Page 51 and 52: Figure 3.7 — Structure of spectra
Page 53 and 54: 4.1 Introduction CHAPTER 4 WAVE FOR
Page 55 and 56: necessary to forecast waves for a p
Page 57 and 58: TABLE 4.4 Additional wave informati
Page 59 and 60: TABLE 4.6 Ranges of swell periods a
Page 61 and 62: this situation, the angular spreadi
Page 63 and 64: the energy flux is c gH 2 . This is
Page 65 and 66: α0, degrees Solution: 80° 70° 60
Page 67 and 68: 5.1 Introduction National Meteorolo
Page 69 and 70: only once, since it is usual to sto
Page 71 and 72: Frequency 0.050 0.067 0.083 0.100 0
Page 73 and 74: The models may differ in several re
Page 75 and 76: The CH class may include many semi-
Page 77 and 78: 6.1 Introductory remarks Since the
Page 79: in some applications, the zero up/d
Page 83 and 84: give large differences in the compa
Page 85 and 86: Wind (m/s) Waves (m) Buoy/GSOWM Wav
Page 87 and 88: TABLE 6.2 Numerical wave models ope
Page 89 and 90: TABLE 6.2 (cont.) Country Name of m
Page 91 and 92: 7.1 Introduction The evolution of w
Page 93 and 94: water boundary into shallow water.
Page 95 and 96: eflected waves, although the latter
Page 97 and 98: Energy (cm 2 /Hz) Energy (cm 2 /Hz)
Page 99 and 100: 8.1 Introduction Wave data are ofte
Page 101 and 102: matter and timing the intervals bet
Page 103 and 104: a Directional Waverider (Barstow et
Page 105 and 106: 80°N 60°N 40°N 20°N 0° -20°S
Page 107 and 108: a combination of sea-surface temper
Page 109 and 110: 8.7.1 Digital analysis of wave reco
Page 111 and 112: 9.1 Introduction Chapter 8 describe
Page 113 and 114: Presentation of data and wave clima
Page 115 and 116: the monsoon season of June to Septe
Page 117 and 118: Probability of non-exceedance case
Page 119 and 120: individual wave height derived usin
Page 121 and 122: emote, data-sparse areas. However,
Page 123 and 124: TABLE 9.2 (cont.) Country Source of
Page 125 and 126: For a storm hindcast, select the mo
Page 127 and 128: TABLE 9.3 (cont.) Country Model use
Page 129 and 130: ANNEX I ABBREVIATIONS AND KEY TO SY
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Abbreviation/ Definition Symbol MOS
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CODE FORM: D . . . . D or IIiii* SE
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sensors, spectral peak wave period
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cs1cs1 The ratio of the spectral de
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M jM j n mn m n smn sm n bn bn b P
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1744 Im Indicator for method of cal
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The following distributions are bri
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4. Weibull distribution Probability
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8. Fisher-Tippett Type I (FT-I) (or
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ANNEX IV THE PNJ (PIERSON-NEUMANN-J
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ANNEX IV 141 Duration graph. Distor
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REFERENCES Abbott, M. B., H. H. Pet
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REFERENCES 145 Carter, D. J. T., P.
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REFERENCES 147 Gumbel, E. J., 1958:
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REFERENCES 149 Maat, N., C. Kraan a
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Slutz, R. J., S. J. Lubker, J. D. H
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SELECTED BIBLIOGRAPHY CERC, 1984: C
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156 Energy . . . . . . . . . . . .
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158 steepness . . . . . . . . . . .
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