Theory and application of calibration techniques for an NDBC directional wave measurements buoy

Steele, Kenneth F.; Lau, Joseph; Hsu, Yu‐Chia

doi:10.1109/joe.1985.1145116

Cited by 54 publications

(17 citation statements)

References 14 publications

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“…Gaps in buoy records from nonoperation (e.g., Figures c and S2–S4), not uncommon during other years not examined here, obscure efforts to establish reliable long‐term trends from buoy records. Furthermore, gaining an understanding of Pacific wave variations, particularly their trends, from buoy estimates is challenged in several ways: (1) the much shorter buoy record (generally beginning in the early 1980s) compared to WW3 model Hs (beginning 1948), (2) large interannual fluctuations, such as the heightened wave activity during strong ENSO episodes [ Bromirski et al ., ] may significantly influence trends, especially if records are short, (3) the sparse buoy spatial coverage that inhibits reliable regional determinations, (4) the problems associated with multiple buoy platforms at the same location [ Gemmrich et al ., ], (5) buoy transfer function calibration issues [ Steele et al ., ], and (6) several decade time series and complete spatial coverage are particularly important to investigate fluctuations and changes in the presence of significant interdecadal storminess variability [ Bromirski et al ., ].…”

Section: Methodsmentioning

confidence: 99%

Wave power variability and trends across the North Pacific

et al. 2013

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[1] Multiyear climate variations influence North Pacific storm intensity and resultant variations in wave energy levels. The timing of these decadal fluctuations and strong El Niño's have had a strong influence on long-term trends. Here we investigate variations in the North Pacific wave power, P W , determined from WAVEWATCH III (WW3) wave model significant wave height, Hs, and peak period data forced by NRA-1 winds spanning the 1948-2008 epoch. Over the entire hindcast, upward trends in Hs and P W , especially in winter, are observed over much of the North Pacific, strongly influenced by an apparent storm intensification after the mid-1970s regime shift. Heightened P W is concentrated in particular regions of the basin, and is associated with increased wave activity during the warm phase of the Pacific Decadal Oscillation (PDO). Wave power events, P E , defined as episodes when Hs exceeded the 90th percentile threshold for at least 12 h, exhibit significant upward trends along much of the U.S. Pacific coast during winter months. Importantly, the hindcast exhibits a recent decrease in P W across much of the North Pacific, in contrast to the long-term increase of P W and Hs. This recent decrease is associated with the prevalent PDO cool phase that developed after the late 1990s. Variability and intensification of coastal P W and P E have important practical implications for shoreline and beach erosion, coastal wetlands inundation, storm-surge flooding, and coastal planning. These considerations will become increasingly important as sea level rises.

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Section: Methodsmentioning

confidence: 99%

Wave power variability and trends across the North Pacific

et al. 2013

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“…Continuous hourly nondirectional wave measurements [ Steele et al , 1985] along the Pacific coast of North America were initiated by NOAA during the early 1980s. Ten NOAA buoys at distributed locations in the northeast (NE) Pacific (Figure 1) were selected for comparison of wave climate parameters covering the 1981–2003 period.…”

Section: Ne Pacific Buoy Datamentioning

confidence: 99%

Wave spectral energy variability in the northeast Pacific

2005

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The dominant characteristics of wave energy variability in the eastern North Pacific are described from NOAA National Data Buoy Center (NDBC) buoy data collected from 1981 to 2003. Ten buoys at distributed locations were selected for comparison based on record duration and data continuity. Long‐period (LP) [T > 12] s, intermediate‐period [6 ≤ T ≤ 12] s, and short‐period [T < 6] s wave spectral energy components are considered separately. Empirical orthogonal function (EOF) analyses of monthly wave energy anomalies reveal that all three wave energy components exhibit similar patterns of spatial variability. The dominant mode represents coherent heightened (or diminished) wave energy along the West Coast from Alaska to southern California, as indicated by composites of the 700 hPa height field. The second EOF mode reveals a distinct El Niño‐Southern Oscillation (ENSO)‐associated spatial distribution of wave energy, which occurs when the North Pacific storm track is extended unusually far south or has receded to the north. Monthly means and principal components (PCs) of wave energy levels indicate that the 1997–1998 El Niño winter had the highest basin‐wide wave energy within this record, substantially higher than the 1982–1983 El Niño. An increasing trend in the dominant PC of LP wave energy suggests that storminess has increased in the northeast Pacific since 1980. This trend is emphasized at central eastern North Pacific locations. Patterns of storminess variability are consistent with increasing activity in the central North Pacific as well as the tendency for more extreme waves in the south during El Niño episodes and in the north during La Niña.

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“…All the data analysed and presented in this paper comes from the Discus-N buoy. Detailed information pertaining to directionalwave measurements with NDBC Discus Buoys, data acquiring, processing and transmitting can be found in Steele, Lau and Hsu (1985) and Steele et al (1990 Figure 1. Geographic location of the SWADE experiment and location of various buoys (Weller et al, 1991).…”

Section: Discussionmentioning

confidence: 99%

Observations of the directional spectrum relaxation of wavefields in slowly and rapidly turning winds

2013

Global NEST Journal

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INTRODUCTIONA representation of the wave energy as a function of frequency, the frequency spectrum, can easily be obtained since it can be extracted from a single record of the water surface elevation at one given location. But surface gravity water waves are not long-crested but rather propagate with appreciable angular spreading about their mean direction. The assumption of a single direction of propagation, common to most engineering applications can potentially lead to significant errors, especially in cases of mixed seas where energy peaks can come from different directions. The specification of wave direction of propagation is by no means simple and the physics leading to this angular spread of energy are not well understood, the main effects being the inherent variability of the source function, and the non-linear effects between wave components and those associated with wave breaking. A more accurate representation of the wave field in the frequency-direction domain will lead to a better understanding of the wave processes, which in turn * to whom all correspondence should be addressed e-mail: tsanis@water.eng.mcmaster.ca ABSTRACT A so called Exact Form of the Maximum Likelihood Method is used to obtain directional spectrum estimates from a 3-meter NDBC discus buoy, part of the Surface Wave Dynamics Experiment (SWADE) field array. The method was used to look at the response of wavefields to turning winds with various wind shift gradients. For slowly turning winds, the spectrum was found to smoothly adjust to the wind changes. As the wind shift gradient increased, a portion of the spectral energy was found to be decoupled from the wind while the bulk of the spectrum smoothly adjusted to the new wind direction. Finally, for even larger wind shift gradients, the preexisting spectrum was completely decoupled from the wind and decayed separately, as a new spectrum consistent with the wind direction was generated. These observations confirm theoretical results previously obtained from a third generation wave model. The relaxation of waves in turning winds was investigated using a simple relaxation model. Correlation coefficients obtained in this study are higher than previously published studies, especially for lower values of the wave age, and a relationship between the relaxation parameter and the wave age is observed.

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Theory and application of calibration techniques for an NDBC directional wave measurements buoy

Cited by 54 publications

References 14 publications

Wave power variability and trends across the North Pacific

Wave power variability and trends across the North Pacific

Wave spectral energy variability in the northeast Pacific

Observations of the directional spectrum relaxation of wavefields in slowly and rapidly turning winds

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