Are There Different Kinds of Rogue Waves?

2006 ◽  
Author(s):  
Paul C. Liu ◽  
Keith R. MacHutchon
Keyword(s):  
Time Series ◽  
Rogue Waves ◽  
Rayleigh Distribution ◽  
The Other ◽  
South Indian Ocean ◽  
Gas Drilling ◽  
Wave Measurements ◽  
South Indian ◽  
Theoretical Considerations

Inasmuch as there is as yet still no universally accepted definition for rogue waves in the ocean, we think there might just be more than one kind of rogue waves to contend with. While the conventional approach has generally designated waves with Hmax/Hs greater than 2.2 as possible rogue waves, based on Rayleigh distribution considerations, there is conspicuously no provision as to how high the ratio of Hmax/Hs can be. In our analysis of wave measurements made from a gas-drilling platform in South Indian Ocean, offshore from Mossel Bay, South Africa, we found a number of cases that indicated Hmax/Hs could be valued in the range between 4 and 10. If this were to be the case these records could be considered to be “uncommon” rogue waves, whereas a record of Hmax/Hs in the range between 2 and 4 could be considered to comprise “typical” rogue waves. On the other hand the spikes in the Hmax data could have been caused by equipment malfunction or some other phenomenon. Clearly the question of whether or not there are different kinds of rogue waves can not be readily answered by theoretical considerations alone and there is a crucial need for long-term wave time series measurements for studying rogue waves.

Are There Different Kinds of Rogue Waves?

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Paul C. Liu ◽  
Keith R. MacHutchon
Keyword(s):  
Rogue Wave ◽  
Rogue Waves ◽  
Rayleigh Distribution ◽  
The Other ◽  
South Indian Ocean ◽  
Gas Drilling ◽  
Wave Measurements ◽  
South Indian ◽  
Theoretical Considerations

There is clearly no immediate answer to the question posted by the title of this paper. Inasmuch as that there are not much definitively known about rogue waves and that there is still no universally accepted definition for rogue waves in the ocean, we think there might just be even more than one kind of rogue waves to contend with. While the conventional approach has generally designated waves with Hmax∕Hs greater than 2.2 as possible rogue waves, based on Rayleigh distribution considerations, there is conspicuously no provision as to how high the ratio of Hmax∕Hs can be and thus not known how high can a rogue wave be. In our analysis of wave measurements made from a gas-drilling platform in South Indian Ocean, offshore from Mossel Bay, South Africa, we found a number of cases that indicated Hmax∕Hs could be valued in the range between 4 and 10. If this were to be the case, then these records could be considered to be “uncommon” rogue waves, whereas a record of Hmax∕Hs in the range between 2 and 4 could be considered to comprise “typical” rogue waves. On the other hand, the spikes in the Hmax data could have been caused by equipment malfunction or some other phenomenon. Clearly, the question of whether or not there are different kinds of rogue waves cannot be readily answered by theoretical considerations alone and there is a crucial need for long-term wave time-series measurements for studying rogue waves.

Sea surface temperatures, salinity and pH reconstructions over the last 1,2 Ma in South Indian Ocean using the unique combination of Mg/Ca, d18O and ∆47 in planktonic foraminifera

2021 ◽  
Author(s):  
Marion Peral ◽  
Thibaut Caley ◽  
Bruno Malaizé ◽  
Erin McClymont ◽  
Thomas Extier ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Transfer Function ◽  
Planktonic Foraminifera ◽  
The Other ◽  
Unique Combination ◽  
South Indian Ocean ◽  
Term Evolution ◽  
South Indian ◽  
Clumped Isotope

<p>The Mid-Pleistocene transition (MPT) took place between 1,200 Ma and 800 ka (still debated). During this transition, the Earth’s orbitally paced ice age cycles intensified, lengthened from ∼40 000 (∼40 ky) to ∼100 ky, and became distinctly asymmetrical while Earth’s orbital variations remained unchanged. Although orbital variations constitute the first order forcing on glacial-interglacial oscillations of the late Quaternary, they cannot explain alone the shifts in climatic periodicity and amplitude observed during the MPT. In order to explain the MPT, long-term evolution of internal mechanisms and feedbacks have been called upon, in relation with the global cooling trend initiated during the Cenozoic, the expansion of Antarctic and Greenland Ice Sheet and/or the long-term decline in greenhouse gases (particularly CO2). A key point is therefore to accurately reconstruction of oceanic temperatures to decipher the processes driving climate variations.</p><p>In the present work, we studied the marine sediment core MD96-2048 taken from south Indian Ocean (26*10’482’’ S, 34*01’148’’ E) in the region of the Agulhas current. We compared 5 paleothermometers: alkenone, TEX86, foraminiferal- transfer function, Mg/Ca and clumped isotope. Among these approaches, carbonate clumped-isotope thermometry (∆<sub>47</sub>) only depends on crystallization temperature, and the ∆<sub>47</sub> relationship with planktonic foraminifer calcification temperature is well defined. Since Mg/Ca is not only controlled by temperature but is also affected by salinity and pH. The classical d<sup>18</sup>O in planktic is dependent on SST and d<sup>18</sup>Osw, which is regionally correlated with the salinity in the present-day ocean. Assuming that the present-day d<sup>18</sup>O<sub>sw</sub>-salinity relation was the same during the MPT, we are able to separate changes in d<sup>18</sup>O<sub>sw</sub> from temperature effects and reconstruct past salinity. Combining d<sup>18</sup>O, Mg/Ca and ∆<sub>47</sub> on planktonic foraminifera allow in theory to reconstruct SST, SSS and pH.</p><p>Here, we measured d<sup>18</sup>O, Mg/Ca and ∆<sub>47</sub> on the shallow-dwelling planktonic species Globigerinioides ruber ss. at the maximal of glacial and interglacial periods over the last 1.2 Ma. Our set of data makes it possible to estimate the long-term evolution of SST, salinity and pH (and thus have an insight into the atmospheric CO<sub>2</sub> concentration) across the MPT. Frist, strong differences are observed between the 5 derived-SST: the alkenone and TEX86 recorded the higher temperatures than the other SST proxies. Alkenone derived-SST do not show glacial-interglacial variations within the MPT. The Mg/Ca and transfer function derived-SST show a good agreement each other, while the clumped-isotope derived-SST are systematically colder than the other derived-SST. Then, our ∆<sub>47</sub>-SST, salinity and pH results clearly show that amplitude of glacial-interglacial variations was insignificant between 1.2 and 0.8 Ma (within the MPT) and increased after the MPT. Finally, we also discussed the potential to use this unique combination of proxies to reconstruct changes of atmospheric CO<sub>2</sub> concentration.</p>

scholarly journals Measurements of vector magnetic anomalies on board the icebreaker Shirase and the magnetization of the ship

1999 ◽  
Vol 42 (2) ◽  
Author(s):  
Y. Nogi ◽  
K. Kaminuma
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Magnetic Anomalies ◽  
The Other ◽  
South Indian Ocean ◽  
Permanent Magnetic Field ◽  
South Indian ◽  
Antarctic Research ◽  
Permanent Magnetization ◽  
Made In

Vector measurements of the geomagnetic field have been made in the South Indian Ocean since 1988 when a Shipboard Three Component Magnetometer (STCM) was installed on board the icebreaker Shirase by the 30th Japanese Antarctic Research Expedition (JARE-30). Twelve constants related to the ship's induced and permanent magnetic field were determined by the data obtained from the JARE-30 to the JARE-35. The constants related to the ship's magnetic susceptibility distribution are almost stable throughout the cruise and mostly depend on the ship's shape. On the other hand, the constants related to the ship's permanent magnetization are variable. However, absolute values of total intensity geomagnetic field calculated from vector geomagnetic field is possible to use, if the constraints from total intensity geomagnetic field measured by the proton magnetometer and/or satellite derived magnetic anomalies are applied.

separating groundwater response to climate and anthropogenic changes using long-term groundwater head time series in the Netherlands

2020 ◽  
Author(s):  
Willem Zaadnoordijk
Keyword(s):  
Time Series ◽  
The Netherlands ◽  
Land Use Changes ◽  
The Other ◽  
Regime Changes ◽  
Base Level ◽  
Groundwater Head ◽  
Groundwater Response ◽  
Groundwater Regime

<div>A set of time series has been investigated which spans more than 50 years of groundwater head measurements throughout the Netherlands.<br>The relation between the groundwater head and precipitation and evaporation has been established using linear transfer noise modeling. This has been done for each entire series and for parts. The latter to detect base level changes and other groundwater regime changes.</div><div>In addition, trends in the other components of the groundwater heads have been investigated as well as possible non linearities in the groundwater response.</div><div>The link is explored between the trends and regime changes from the time series models on one hand and anthropogenic (land use) changes and climate change on the other hand.</div><div> </div>

scholarly journals Direction of Causality between Financial Development and Economic Growth in Turkey

2021 ◽  
pp. 22-37
Author(s):  
Cengiz Yılmaz ◽  
Banu Demirhan
Keyword(s):  
Economic Growth ◽  
Time Series ◽  
Gross Domestic Product ◽  
Financial Development ◽  
The Other ◽  
Development Indicators ◽  
Short Run ◽  
Causality Relationship ◽  
Using Data

This paper has investigated the causality relationship between financial development and economic growth in Turkey, using data from 2005:04 to 2020:03. We construct a time-series model to explore causality relationships between the variables. In the study, two indicators were used as financial development indicators: banking loans to the private sector and money supply to GDP (Gross Domestic Product). The empirical results have represented a bi-directional relationship between financial development and economic growth in the short run. On the other hand, we have not found a causality relationship in the long term.

scholarly journals A taxonomic and distributional survey of marine benthonic Ostracoda off Kerguelen and Heard Islands, South Indian Ocean

2004 ◽  
Vol 23 (1) ◽  
pp. 15-38 ◽  
Author(s):  
Michael A. Ayress ◽  
Patrick De Deckker ◽  
Graham P. Coles
Keyword(s):  
Deep Sea ◽  
The Other ◽  
Intermediate Water ◽  
Kerguelen Plateau ◽  
South Indian Ocean ◽  
Sw Pacific ◽  
South Indian ◽  
Two New Species ◽  
The Common ◽  
Ostracod Species

Abstract. From an examination of 34 grab and dredge samples ranging from 110 m to 3584 m water depth, collected during Eltanin cruise 47 across the Kerguelen Plateau, 26 shallow-water and 35 deep-sea benthonic ostracod species have been identified. Systematic notes and illustrations of the common and some of the rare species are presented. Two new species are described: Philoneptunus cassidyi n. sp. and Taracythere abyssora n. sp. Comparisons made with the Atlantic and SW Pacific Oceans and circum-Antarctic regions indicate that the fauna comprises dominantly cosmopolitan deep-sea species while most of the other species have close affinities with the SW Pacific. In the Kerguelen material, seven distinct depth assemblages appear to correspond well with differing watermasses and there is evidence that the relatively shallow position of Antarctic Intermediate Water permits elevation of the upper depth limits of some deep-sea species. Some species have developed ornament of fine reticulation, features not previously seen in those species outside the Kerguelen region.

Sea State Duration and Probability of Occurrence of a Freak Crest

2003 ◽  
Author(s):  
Elzbieta Bitner-Gregersen
Keyword(s):  
Time Series ◽  
Significant Wave Height ◽  
The Other ◽  
Design Practice ◽  
Extreme Wave ◽  
Sea State ◽  
State Duration ◽  
Current Design ◽  
Direct Extrapolation

For design purpose extreme wave crests can be determined by direct extrapolation or by estimating an extreme sea state condition. In the latter procedure it is common to estimate a n-year Hs level as a fractile of a marginal long-term distribution of significant wave height, combined with adequately chosen characteristics values for the other sea-state parameters. In this approach a sea state duration needs to be assumed when extremes are calculated. In the present study sensitivity of extreme crest characteristics to an assumed sea state duration is investigated for wave records which include a freak event. The wave time series recorded at the Draupner platform, January 1, 1995, and the data registered at Ekofisk, October 25, 1998, are used in the analysis. Predictions of several models are compared with the prediction given by the 2nd order Forristall crest distribution. Implications of the results for the current design practice are discussed.

scholarly journals Solar radiation trend across China in recent decades: a revisit with quality-controlled data

2010 ◽  
Vol 10 (8) ◽  
pp. 18389-18418 ◽  
Author(s):  
W.-J. Tang ◽  
K. Yang ◽  
J. Qin ◽  
C. C. K. Cheng ◽  
J. He
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Solar Radiation ◽  
The Other ◽  
Continuous Data ◽  
China Meteorological Administration ◽  
Surface Solar Radiation ◽  
Factors Affecting ◽  
Term Variation

Abstract. Solar radiation is one of the most important factors affecting climate and environment, and its long-term variation is of much concern in climate change studies. In the light of the limited number of radiation stations with reliable long-term time series observations, this paper presents a new evaluation of the long-term variation of surface solar radiation over China by combining quality-controlled observed data and two radiation models. One is the ANN-based (Artificial Neutral Network) model and the other is a physical one. The two models produced radiation trends comparable to the observed ones at a few stations possessing reliable and continuous data. Then, the trend estimation is extended by the ANN-based model to all 96 radiation stations and furthermore extended by the physical model to all 716 China Meteorological Administration (CMA) routine stations. The new estimate trend is different from previous ones in two aspects. First, the magnitude of solar radiation over China decreased by about −0.19 W m−2 yr−1 between 1961 and 2000, which is greatly less in magnitude than trends estimated in previous studies (ranging over −0.41 to −0.52 W m−2 yr−1). Second, the "From Dimming to Brightening" transition in China during the late 1980s and the early 1990s was addressed in previous studies, but this study indicates the solar radiation reached a stable level since the 1990s and the transition is not noticeable. These differences are attributed to inappropriate data and approaches in previous studies.

Historical trends in spring ice breakup for the Aura River in Southwest Finland, AD 1749–2018

The Holocene ◽  
2019 ◽  
Vol 29 (6) ◽  
pp. 953-963 ◽  
Author(s):  
Stefan Norrgård ◽  
Samuli Helama
Keyword(s):  
Time Series ◽  
18Th Century ◽  
The Other ◽  
Historical Trends ◽  
Single Time ◽  
Climate Research ◽  
Ice Breakup ◽  
Different Types ◽  
Long Term Trends

Ice breakup (IBU) observations have been recorded for Aura River in Turku, southwest Finland, since the mid-18th century. The latest long-term investigation covered the period 1749–1906, but the series contains several biases. In this article, we present a fully revised and extended IBU series (1749–2018) of Aura River for climate research purposes. Instead of typical univariate IBU data (a single time series with one data point per year), this series includes three different types of IBU data. These are the initial observations of the ice starting to break up (IBU1), the river recorded as free from ice within city limits (IBU2) and, finally, the arrival of the ice from behind the Halinen dam, the so-called Halinen ice (IBU3). The IBU1 series shows negative, statistically significant long-term trends since 1749. While the other two phenological events also exhibit negative long-term trends, indicative of earlier and warmer springs towards the present day, their trends are not significant over multi-centurial scales. The IBU2 series is the only series covering the entire period, and it shows a significant negative trend towards earlier breakups (16 days) between 1919 and 2018. Consequently, breakups in March, which were extremely rare before the 1900s, have become common, while breakups in May (previously once per decade) have not occurred since 1881. These results are indicative of sub-seasonal trends in the breakups. Our results also confirm defects in the previous time series, which shows a bias of up to 16 days.

scholarly journals The Dynamics of Beech Roundwood Prices in Selected Central European Markets

Forests ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 902
Author(s):  
Anna Kożuch ◽  
Jan Banaś
Keyword(s):  
Time Series ◽  
Large Diameter ◽  
The Other ◽  
Seasonal Effects ◽  
Type I ◽  
German Market ◽  
Price Series ◽  
Other Hand ◽  
Cointegration Tests

The European beech (Fagus sylvatica L.) is the most prevalent deciduous tree species in Central Europe. The implementation of sustainable, close-to-nature silvicultural practices increased the percentage share of beech in forest species composition, raising the economic significance of beech roundwood, especially in terms of revenues from timber sales. The elucidation of roundwood price mechanisms as well as long-term equilibrium relations between international markets may be helpful in calculating the profitability of beech roundwood production. The study material consists of quarterly time series of beech roundwood prices from Austria, Czechia, Germany, Poland, Slovakia, and Slovenia in the years 2005–2018. The price time series were described with a multiplicative model incorporating seasonal, cyclical, and irregular, as well as long-term trend components. The time series were decomposed using the Census X11 method. Stationarity was tested by means of the augmented Dickey–Fuller test (ADF) and the Kwiatkowski–Phillips–Schmidt–Shin test (KPSS). Cointegration was assessed using the Johansen and Engle–Granger methods. From 2005–2018, the highest mean beech roundwood prices were found for Austria (77.5 € m−3) and Germany, and the lowest for Poland and Slovakia. Roundwood prices were badly affected by the 2008/2009 financial crisis, which caused an approx. 27% decline. The prices of large-diameter beech logs exhibited seasonal fluctuations, typically reaching a maximum in Q1 and a minimum in Q3. The amplitude of those fluctuations was the highest in Slovenia in 2005 (10.1%), while in Czechia and Germany, seasonal effects increased over the period of study. The lowest seasonality was found in Slovakia and Austria (in the latter country it was not statistically significant). On an annual scale, cyclical changes generally accounted for the largest proportion of price variation, and were particularly pronounced in Poland (78.9%), Slovakia (78.6%), and Austria (69.2%). On the other hand, seasonal effects were predominant in the Slovenian (40.6%), German (34.1%), and Czech (33.3%) markets. In countries with price series of type I(0), simple correlation between stationary beech roundwood prices is positive and the strongest between Czechia–Poland and Czechia–Austria; on the other hand they are the weakest in the German market. In Slovakia and Slovenia with nonstationary price series, both Johansen’s and Engle-Granger’s cointegration tests indicated the absence of a long-term equilibrium between the analyzed beech timber markets. Results revealed integration between the prices of large-diameter beech logs in Czechia, Austria, and Poland. It should be mentioned that in this study, the time series of price used are rather short for long time cointegration analysis, which might prevent the proper detection of cointegration between all analyzed countries.

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