GPS height time series: Short-period origins of spurious long-period signals

Abstract The objective of this paper is to introduce a new analysis methodology for assessment of riser fatigue due to slugging. Under certain flow regimes, a multiphase (oil-gas-water) flow can result in slug flow, in which a sequence of relatively high density slugs and relatively low density bubbles propagate along the flowline and the riser. The variation of slug and bubble density at a location with time is random, and slug characteristics can also change significantly along the riser length. Due to local and global weight variations, the riser undergoes cycles of bending which cause fatigue. By explicitly modeling full spatial and temporal variability and randomness of slugs, the new analysis method is significantly more accurate than other methods and it captures physics of riser's slugging response. The slugging fatigue of a steel lazy wave riser was analyzed in Orcaflex software by modeling a repeating pair of slug and bubble with constant slug and bubble densities and associated lengths over the 3-hour simulation time. A separate slug train was propagated in five sub-segments of the riser. To model a more accurate and realistic representation of slugging behavior, the time series of density was extracted at each node from the multiphase flow simulator Olga. Statistical and spectral analysis of the Olga output showed that assumptions of constant slug-bubble density, and of slug behavior being uniform over long segments of riser are too simplistic. Therefore, full time series of density at each node was input into the riser analysis using the existing capabilities of Orcaflex software. As the Orcaflex slug form approach was computationally expensive, we also developed an extrenal slug loader, which provides same level of accuracy while being computationally fast and full automated. The new method shows that the cyclic riser response at the touchdown point (TDP) is composed of two parts. One is the relatively short period (~20-60 seconds) fluctuations that occur because of local weight variations as a slug-bubble passes a riser node. The other is the relatively long period (~10-30 minutes) fluctuations that occur due to global weight variations, which are due to spatial integration of density time series over the lower catenary. These long period fluctuations drive the TDP fatigue. Preliminary field measurements with an ROV, while inducing temporary slugging in the riser, confirmed analytical predictions of long period and high amplitude motions at hog bend. This paper presents a new and significantly more accurate method for analyzing riser fatigue due to slugging. Previously unknown behavior of very long period and high amplitude riser motions is identified and explained. SLWR response to slugging can be an important contributor to the overall fatigue design budget especially at the TDP. This work reflects ExxonMobil's on-going efforts to ensure that we maintain safe designs as we adopt systems new to us in new and challenging environments.

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Improving Stage–Discharge Relation in The Mekong River Estuary by Remotely Sensed Long-Period Ocean Tides

Remote Sensing ◽

10.3390/rs12213648 ◽

2020 ◽

Vol 12 (21) ◽

pp. 3648

Author(s):

Hongrui Peng ◽

Hok Sum Fok ◽

Junyi Gong ◽

Lei Wang

Keyword(s):

Time Series ◽

Water Level ◽

Water Discharge ◽

Remotely Sensed ◽

Tidal Height ◽

Global Ocean ◽

Ocean Tide ◽

Ocean Tides ◽

Long Period ◽

Short Period

Ocean tidal backwater reshapes the stage–discharge relation in the fluvial-to-marine transition zone at estuaries, rendering the cautious use of these data for hydrological studies. While a qualitative explanation is traditionally provided by examining a scatter plot of water discharge against water level, a quantitative assessment of long-period ocean tidal effect on the stage–discharge relation has been rarely investigated. This study analyzes the relationship among water level, water discharge, and ocean tidal height via their standardized forms in the Mekong Delta. We found that semiannual and annual components of ocean tides contribute significantly to the discrepancy between standardized water level and standardized water discharge time series. This reveals that the long-period ocean tides are the significant factors influencing the stage–discharge relation in the river delta, implying a potential of improving the relation as long as proper long-period ocean tidal components are taken into consideration. By isolating the short-period signals (i.e., less than 15 days) from land surface hydrology and ocean tides, better consistent stage–discharge relations are obtained, in terms of improving the Pearson correlation coefficient (PCC) from ~0.4 to ~0.8 and from ~0.6 to ~0.9 for the stations closest to the estuary and at the Mekong Delta entrance, respectively. By incorporating the long-period ocean tidal height time series generated from a remotely sensed global ocean tide model into the stage–discharge relation, further refined stage–discharge relations are obtained with the PCC higher than 0.9 for all employed stations, suggesting the improvement of daily averaged water level and water discharge while ignoring the short-period intratidal variability. The remotely sensed global ocean tide model, OSU12, which contains annual and semiannual ocean tide components, is capable of generating accurate tidal height time series necessary for the partial recovery of the stage–discharge relation.

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Discussion following the presentation by F. Deubner

International Astronomical Union Colloquium ◽

10.1017/s0252921100053240 ◽

1977 ◽

Vol 36 ◽

pp. 69-74

Keyword(s):

List Type ◽

The Sun ◽

Type Number ◽

Harmonic Motion ◽

Locally Excited ◽

Long Period ◽

Coherent Wave ◽

Short Period ◽

Global Modes

The discussion was separated into 3 different topics according to the separation made by the reviewer between the different periods of waves observed in the sun :1) global modes (long period oscillations) with predominantly radial harmonic motion.2) modes with large coherent - wave systems but not necessarily global excitation (300 s oscillation).3) locally excited - short period waves.

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Isolation and Analysis of Six timeless Alleles That Cause Short- or Long-Period Circadian Rhythms in Drosophila

Genetics ◽

10.1093/genetics/156.2.665 ◽

2000 ◽

Vol 156 (2) ◽

pp. 665-675

Author(s):

Adrian Rothenfluh ◽

Marla Abodeely ◽

Jeffrey L Price ◽

Michael W Young

Keyword(s):

Nuclear Translocation ◽

Phase Response Curve ◽

Fixed Number ◽

Constant Darkness ◽

Genetic Screens ◽

Protein Levels ◽

Long Period ◽

Short Period ◽

Molecular Oscillation ◽

New Alleles

Abstract In genetic screens for Drosophila mutations affecting circadian locomotion rhythms, we have isolated six new alleles of the timeless (tim) gene. Two of these mutations cause short-period rhythms of 21–22 hr in constant darkness, and four result in long-period cycles of 26–28 hr. All alleles are semidominant. Studies of the genetic interactions of some of the tim alleles with period-altering period (per) mutations indicate that these interactions are close to multiplicative; a given allele changes the period length of the genetic background by a fixed percentage, rather than by a fixed number of hours. The timL1 allele was studied in molecular detail. The long behavioral period of timL1 is reflected in a lengthened molecular oscillation of per and tim RNA and protein levels. The lengthened period is partly caused by delayed nuclear translocation of TIML1 protein, shown directly by immunocytochemistry and indirectly by an analysis of the phase response curve of timL1 flies.

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Wave Force Characteristics of Large-Sized Offshore Wind Support Structures to Sea Levels and Wave Conditions

Applied Sciences ◽

10.3390/app9091855 ◽

2019 ◽

Vol 9 (9) ◽

pp. 1855

Author(s):

Youn-Ju Jeong ◽

Min-Su Park ◽

Jeongsoo Kim ◽

Sung-Hoon Song

Keyword(s):

Shallow Water ◽

Wave Height ◽

Wave Force ◽

Diffraction Effect ◽

Support Structures ◽

Sea Levels ◽

Irregular Wave ◽

Long Period ◽

Short Period ◽

Period Wave

This paper presents the results of wave force tests conducted on three types of offshore support structures considering eight waves and three sea levels to investigate the corresponding wave forces. As a result of this study, it is found that the occurrence of shoaling in shallow water induces a significant increase of the wave force. Most of the test models at the shallow water undergo a nonlinear increase of the wave force with higher wave height increasing. In addition, the larger the diameter of the support structure within the range of this study, the larger the diffraction effect is, and the increase in wave force due to shoaling is suppressed. Under an irregular wave at the shallow water, the wave force to the long-period wave tends to be slightly higher than that of the short period wave since the higher wave height component included in the irregular wave has an influence on the shoaling. In addition, it is found that the influence of shoaling under irregular wave becomes more apparent in the long period.

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Reply to "Comment on 'Statistical Features of Short-Period and Long-Period Near-Source Ground Motions' by Masumi Yamada, Anna H. Olsen, and Thomas H. Heaton" by Roberto Paolucci, Carlo Cauzzi, Ezio Faccioli, Marco Stupazzini, and Manuela Villani

Bulletin of the Seismological Society of America ◽

10.1785/0120100210 ◽

2011 ◽

Vol 101 (2) ◽

pp. 919-924 ◽

Cited By ~ 1

Author(s):

M. Yamada ◽

A. H. Olsen ◽

T. H. Heaton

Keyword(s):

Ground Motions ◽

Statistical Features ◽

Long Period ◽

Short Period

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Epistatic and Synergistic Interactions Between Circadian Clock Mutations in Neurospora crassa

Genetics ◽

10.1093/genetics/159.2.537 ◽

2001 ◽

Vol 159 (2) ◽

pp. 537-543

Author(s):

Louis W Morgan ◽

Jerry F Feldman

Keyword(s):

Circadian Clock ◽

Neurospora Crassa ◽

Mutant Strain ◽

Temperature Compensation ◽

Double Mutant ◽

Synergistic Interactions ◽

Long Period ◽

Double Mutant Strain ◽

Short Period ◽

Compensation Mechanisms

Abstract We identified a series of epistatic and synergistic interactions among the circadian clock mutations of Neurospora crassa that indicate possible physical interactions among the various clock components encoded by these genes. The period-6 (prd-6) mutation, a short-period temperature-sensitive clock mutation, is epistatic to both the prd-2 and prd-3 mutations. The prd-2 and prd-3 long-period mutations show a synergistic interaction in that the period length of the double mutant strain is considerably longer than predicted. In addition, the prd-2 prd-3 double mutant strain also exhibits overcompensation to changes in ambient temperature, suggesting a role in the temperature compensation machinery of the clock. The prd-2, prd-3, and prd-6 mutations also show significant interactions with the frq7 long-period mutation. These results suggest that the gene products of prd-2, prd-3, and prd-6 play an important role in both the timing and temperature compensation mechanisms of the circadian clock and may interact with the FRQ protein.

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LONG-PERIOD SURFACE-RELATED MULTIPLE SUPPRESSION IN 2D MARINE SEISMIC DATA USING PREDICTIVE DECONVOLUTION AND COMBINATION OF SURFACE-RELATED MULTIPLE ELIMINATION AND PARABOLIC RADON FILTERING

10.32008/geolinks2021/b1/v3/30 ◽

2021 ◽

Author(s):

Pimpawee Sittipan ◽

Pisanu Wongpornchai

Keyword(s):

Seismic Data ◽

Seismic Reflection ◽

Petroleum Reservoirs ◽

The United States ◽

Multiple Reflections ◽

Long Period ◽

Predictive Deconvolution ◽

Short Period ◽

Marine Seismic ◽

Multiple Elimination

Some of the important petroleum reservoirs accumulate beneath the seas and oceans. Marine seismic reflection method is the most efficient method and is widely used in the petroleum industry to map and interpret the potential of petroleum reservoirs. Multiple reflections are a particular problem in marine seismic reflection investigation, as they often obscure the target reflectors in seismic profiles. Multiple reflections can be categorized by considering the shallowest interface on which the bounces take place into two types: internal multiples and surface-related multiples. Besides, the multiples can be categorized on the interfaces where the bounces take place, a difference between long-period and short-period multiples can be considered. The long-period surface-related multiples on 2D marine seismic data of the East Coast of the United States-Southern Atlantic Margin were focused on this research. The seismic profile demonstrates the effectiveness of the results from predictive deconvolution and the combination of surface-related multiple eliminations (SRME) and parabolic Radon filtering. First, predictive deconvolution applied on conventional processing is the method of multiple suppression. The other, SRME is a model-based and data-driven surface-related multiple elimination method which does not need any assumptions. And the last, parabolic Radon filtering is a moveout-based method for residual multiple reflections based on velocity discrimination between primary and multiple reflections, thus velocity model and normal-moveout correction are required for this method. The predictive deconvolution is ineffective for long-period surface-related multiple removals. However, the combination of SRME and parabolic Radon filtering can attenuate almost long-period surface-related multiple reflections and provide a high-quality seismic images of marine seismic data.

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Estimating contribution of high-frequency sea-level oscillations to the extreme sea levels in the Adriatic Sea

10.5194/egusphere-egu21-4602 ◽

2021 ◽

Author(s):

Krešimir Ruić ◽

Jadranka Šepić ◽

Maja Karlović ◽

Iva Međugorac

Keyword(s):

Time Series ◽

Sea Level ◽

High Frequency ◽

Adriatic Sea ◽

Tide Gauge ◽

Data Series ◽

Sea Levels ◽

Short Period ◽

Extreme Sea Levels ◽

Sea Level Oscillations

Extreme sea levels are known to hit the Adriatic Sea and to occasionally cause floods that produce severe material damage. Whereas the contribution of longer-period (T > 2 h) sea-level oscillations to the phenomena has been well researched, the contribution of the shorter period (T <&#160;2 h) oscillations is yet to be determined. With this aim, data of 1-min sampling resolution were collected for 20 tide gauges, 10 located at the Italian (north and west) and 10 at the Croatian (east) Adriatic coast. Analyses were done on time series of 3 to 15 years length, with the latest data coming from 2020, and with longer data series available for the Croatian coast. Sea level data were thoroughly checked, and spurious data were removed.&#160;For each station, extreme sea levels were defined as events during which sea level surpasses its 99.9 percentile value. The contribution of short-period oscillations to extremes was then estimated from corresponding high-frequency (T < 2 h) series. Additionally, for four Croatian tide gauge stations (Rovinj, Bakar, Split, and Dubrovnik), for period of 1956-2004, extreme sea levels were also determined from the hourly sea level time series, with the contribution of short-period oscillations visually estimated from the original tide gauge charts.&#160;&#160;Spatial and temporal distribution of contribution of short-period sea-level oscillations to the extreme sea level in the Adriatic were estimated. It was shown that short-period sea-level oscillation can significantly contribute to the overall extremes and should be considered when estimating flooding levels.&#160;

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Analysis of the eastern Adriatic sea-level extremes

10.5194/egusphere-egu21-5676 ◽

2021 ◽

Author(s):

Marija Pervan ◽

Jadranka Šepić

Keyword(s):

Sea Level ◽

Adriatic Sea ◽

Hot Spot ◽

Storm Surges ◽

Low Pressure ◽

Long Period ◽

Short Period ◽

Sea Level Oscillations ◽

Low Pass ◽

Level Height

The Adriatic Sea is known to be under a high flooding risk due to both storm surges and meteorological tsunamis, with the latter defined as short-period sea-level oscillations alike to tsunamis but generated by atmospheric processes. In June 2017, a tide-gauge station with a 1-min sampling resolution has been installed at Stari Grad (middle Adriatic Sea), the well-known meteotsunami hot-spot, which is, also, often hit by storm surges.&#160;Three years of corresponding sea-level measurements were analyzed, and 10 strongest episodes of each of the following extreme types were extracted from the residual series: (1) positive long-period (T > 210 min) extremes; (2) negative long-period (T > 210 min) extremes; (3) short-period (T < 210) extremes. Long-period extremes were defined as situations during which sea level surpasses (is lower than) 99.7 (i.e. 2) percentile of sea level height, and short-period extremes as situations during which variance of short-period sea-level oscillations is higher than 99.4 percentile of total variance[J1]&#160; of short-period series. A strong seasonal signal was detected for all extremes, with most of the positive long-period extremes appearing during November to February, and most of the negative long-period extremes during January to February. As for the short-period extremes, these appear evenly throughout the year, but strongest events seem to appear during May to July.All events were associated to characteristic atmospheric situations, using both local measurements of the atmospheric variables, and ERA5 Reanalysis dataset. It was shown that positive low-pass extremes commonly appear during presence of low pressure over the Adriatic associated with strong SE winds (&#8220;sirocco&#8221;), and negative low-pass extremes are associated to the high atmospheric pressure over the area associated with either strong NE winds (&#8220;bora&#8221;), or no winds at all. On the other hand, high-pass sea level extremes are noticed during two distinct types of atmospheric situations corresponding to both &#8220;bad&#8221; (low pressure, strong SE wind) and &#8220;nice&#8221; (high pressure, no wind) weather.It is particularly interesting that short-period extremes, of which strongest are meteotsunamis, are occasionally coincident with positive long-period extremes contributing with up to 50 percent to total sea level height &#8211; thus implying existence of a double danger phenomena (meteotsunami + storm surge).&#160;

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