scholarly journals A gridded surface current product for the Gulf of Mexico from consolidated drifter measurements

2021 ◽  
Vol 13 (2) ◽  
pp. 645-669
Author(s):  
Jonathan M. Lilly ◽  
Paula Pérez-Brunius
Keyword(s):  
Gulf Of Mexico ◽  
Temporal Distribution ◽  
Surface Current ◽  
Large Set ◽  
Surface Currents ◽  
Important Region ◽  
Surface Drifter ◽  
Current Product ◽  
The Mean ◽  
Separate Product

Abstract. A large set of historical surface drifter data from the Gulf of Mexico – 3770 trajectories spanning 28 years and more than a dozen data sources – are collected, uniformly processed and quality controlled, and assimilated into a spatially and temporally gridded dataset called GulfFlow. This dataset is available in two versions, with 1/4∘ or 1/12∘ spatial resolution respectively, both of which have overlapping monthly temporal bins with semimonthly spacing and which extend from the years 1992 through 2020. Together these form a significant resource for studying the circulation and variability in this important region. The uniformly processed historical drifter data from all publicly available sources, interpolated to hourly resolution, are also distributed in a separate product called GulfDriftersOpen. Forming a mean surface current map by directly bin-averaging the hourly drifter data is found to lead to severe artifacts, a consequence of the extremely inhomogeneous temporal distribution of the drifters. Averaging instead the already monthly-averaged data in GulfFlow avoids these problems, resulting in the highest-resolution map of the mean Gulf of Mexico surface currents yet produced. The consolidated drifter dataset is freely available at https://doi.org/10.5281/zenodo.3985916 (Lilly and Pérez-Brunius, 2021a), while the gridded products are available for noncommercial use only (for reasons discussed herein) at https://doi.org/10.5281/zenodo.3978793 (Lilly and Pérez-Brunius, 2021b).

scholarly journals A gridded surface current product for the Gulf of Mexico from consolidated drifter measurements

2020 ◽  
Author(s):  
Jonathan M. Lilly ◽  
Paula Pérez-Brunius
Keyword(s):  
Gulf Of Mexico ◽  
Temporal Distribution ◽  
Surface Current ◽  
Large Set ◽  
Surface Currents ◽  
Important Region ◽  
Surface Drifter ◽  
Current Product ◽  
The Mean ◽  
Separate Product

Abstract. A large set of historical surface drifter data from the Gulf of Mexico – 3761 trajectories spanning 27 years and more than a dozen data sources – are collected, uniformly processed and quality controlled, and assimilated into a spatially and temporally gridded dataset called GulfFlow. This dataset is available in two versions, with one-quarter degree or one-twelfth degree spatial resolution respectively, both of which have overlapping monthly temporal bins with semimonthly spacing, and extend from the years 1992 through 2019. Together these form a significant resource for studying the circulation and variability in this important region. The uniformly processed historical drifter data interpolated to hourly resolution from all publicly available sources are also distributed in a separate product called GulfDriftersOpen. Forming a mean surface current map by directly bin-averaging the hourly drifter data is found to lead to severe artifacts, a consequence of the extremely inhomogeneous temporal distribution of the drifters. Averaging instead the already monthly-averaged data in GulfFlow avoids these problems, resulting in the highest-resolution map of the mean Gulf of Mexico surface currents yet produced. The consolidated drifter dataset is freely available from https://doi.org/10.5281/zenodo.3985916 (Lilly and Pérez-Brunius, 2020a), while the gridded products are available for noncommercial use at https://doi.org/https://doi.org/10.5281/zenodo.3978793 (Lilly and Pérez-Brunius, 2020b), the latter being freely available for noncommercial use only for reasons discussed herein.

The action of a surface current used as a breakwater

1955 ◽  
Vol 231 (1187) ◽  
pp. 466-478 ◽  
Keyword(s):  
Surface Current ◽  
Water Current ◽  
Air Bubbles ◽  
Surface Currents ◽  
Mean Velocity ◽  
Uniform Velocity ◽  
Sea Bottom ◽  
The Mean ◽  
Perforated Tube ◽  
A Current

The conditions under which an outward-flowing surface current can prevent the passage of waves coming in from the sea are investigated mathematically. Two types of current are considered: ( a ) a current with uniform velocity extending to a depth h ; ( b ) a current with velocity decreasing uniformly and vanishing at depth h . They have very similar effects. The mean velocity required to stop waves of given frequency is rather greater in case ( a ) than in case ( b ). The water current produced by a curtain of air bubbles from a perforated tube on the sea bottom is investigated theoretically on the assumption that the bubbles are very small. Evans (1955) has measured the surface currents produced in a tank by a bubble curtain and finds them smaller than predicted. The discrepancy is partly due to the fact that the bubbles were not very small.

Use of a Stem Device for VIV Mitigation on a Dry Tree Semi-Submersible

2009 ◽  
Author(s):  
Apurva Gupta ◽  
John Murray ◽  
Bin Li ◽  
Harish Mukundan ◽  
Anis Hussain
Keyword(s):  
Gulf Of Mexico ◽  
Fatigue Damage ◽  
Production Systems ◽  
High Surface ◽  
Surface Current ◽  
Water Current ◽  
Surface Currents ◽  
Offshore Industry ◽  
Viv Suppression ◽  
Tree Production

The offshore industry is devoting considerable effort to develop a dry tree production Semi-submersible with motion characteristics similar to a Spar but with the functionality of a Tension Leg Platform (TLP) or a Semi-submersible in terms of fabrication, installation and commissioning. Installation of these Semi-submersibles in the Gulf of Mexico environment exposes the risers to high surface current which result in high fatigue damage due to Vortex Induced Vibration (VIV). In the existing dry tree production systems, the Spar shields the riser from the high velocity surface currents in depths to approximately 600 ft. In the dry tree Semi-submersible the upper sections of the risers are exposed to surface currents. In addition, most dry tree Semi-submersibles designs have to support Keel Joints similar to a Spar. Thus, installing and replacing conventional VIV mitigation devices like the fairings and strakes could become difficult. In comparison, the TLP has no keel guides making it easier to install risers with strakes or fairings to improve the riser’s response to currents in terms of VIV. There are two basic proven techniques to reduce VIV damage on a riser. These involve application of standard fairings or strakes and direct protection of an exposed riser to currents. This paper discusses a methodology for VIV suppression using a riser stem. This mechanism does not reduce the VIV directly on the riser, but it in fact shields the riser from the surface currents, and thus reduces the fatigue damage on risers. This riser is shielded inside a conduit section called a stem which extends from the deck of the Semi-submersible to the keel. The paper quantifies and discusses the reduction in fatigue damage when the stem is used. The analysis is based on typical deep water current conditions for the Gulf of Mexico.

Comparisons of Scatterometer and TAO Winds Reveal Time-Varying Surface Currents for the Tropical Pacific Ocean*

2005 ◽  
Vol 22 (6) ◽  
pp. 735-745 ◽  
Author(s):  
Kathryn A. Kelly ◽  
Suzanne Dickinson ◽  
Gregory C. Johnson
Keyword(s):  
Southern Oscillation ◽  
Surface Current ◽  
Current Data ◽  
Surface Currents ◽  
Radar Altimeter ◽  
Near Surface ◽  
The Mean ◽  
Divergence Pattern ◽  
Acoustic Doppler Current Profilers ◽  
Good Agreement

Abstract The differences between Tropical Atmosphere Ocean (TAO) anemometer and QuikSCAT scatterometer winds are analyzed over a period of 3 yr. Systematic differences are expected owing to ocean currents because the anemometer measures absolute air motion, whereas a radar measures the motion of the air relative to the ocean. Monthly averaged collocated wind differences (CWDs) are compared with available near-surface current data at 15-m depth from drifters, at 25-m depth from acoustic Doppler current profilers (ADCPs), and at 10-m depth from current meters and with geostrophic currents at the surface from the TOPEX/Poseidon radar altimeter. Because direct current observations are so sparse, comparisons are also made with climatological currents from these same sources. Zonal CWDs are in good agreement with the zonal current observations, particularly from 2°S to 2°N where there are strong currents and a robust seasonal cycle, with the altimeter-derived anomalous currents giving the best match. At higher latitudes there is qualitative agreement at buoys with relatively large currents. The overall variance of the zonal component of the CWDs is reduced by approximately 25% by subtracting an estimate of the zonal currents. The meridional CWDs are nearly as large as the zonal CWDs but are unpredictable. The mean CWDs show a robust divergence pattern about the equator, which is suggestive of Ekman currents, but with unexpectedly large magnitudes. Coefficients for estimating climatological zonal surface currents from the altimeter at the TAO buoys are tabulated: the amplitudes and phases for the annual and semiannual harmonics, and a linear regression against the Southern Oscillation index, are combined with the mean from the drifter currents. Examples are shown of the application of these estimators to data from SeaWinds on the Midori satellite. These estimators are also useful for deriving air–sea fluxes from TAO winds.

scholarly journals Near-Surface and Deep Circulation Coupling in the Western Gulf of Mexico

2018 ◽  
Vol 48 (1) ◽  
pp. 145-161 ◽  
Author(s):  
M. Tenreiro ◽  
Julio Candela ◽  
Enric Pallàs Sanz ◽  
Julio Sheinbaum ◽  
José Ochoa
Keyword(s):  
Gulf Of Mexico ◽  
Surface Currents ◽  
Loop Current ◽  
Cyclonic Gyre ◽  
Cyclonic Vorticity ◽  
Near Surface ◽  
Deep Circulation ◽  
Rear Part ◽  
The Mean ◽  
Mean Circulation

AbstractThe coupling between the upper (z < 1000-m depth) and deep (z > 1500 m) circulation in the western Gulf of Mexico (WGoM) driven by the arrival of Loop Current eddies (LCEs) is analyzed from moorings measuring horizontal velocity in the full water column during a 5-yr period (October 2008–October 2013). Nine LCEs crossing the mooring array are documented. A composite of these events shows that strong northward currents at depth having speeds of 0.1–0.2 m s−1 precede (~10–20 days) the strong northward near-surface currents (~0.5 m s−1) characteristic of the western rim of the LCEs. These deep northward flow intensifications are followed by southward deep flows coupled with the surface-intensified southward current of the eastern (rear) part of the LCEs crossing the array. These results are consistent with the existence of a deep anticyclone leading and a cyclone trailing the upper-layer LCEs. Objectively interpolated regional maps of velocities and vertical vorticity obtained from up to 30 moorings indicate the mean circulation at 100-m depth in the northern WGoM is mostly anticyclonic and enhanced by the arrival of the westward-propagating LCEs, while the southern part is dominated by the presence of a semipermanent cyclonic structure (Bay of Campeche cyclonic gyre). At 1500-m depth, the mean circulation follows the slope in a cyclonic sense and shows a cyclonic vorticity maximum on the abyssal plane consistent with the LCE deep flow composites. This suggests the LCEs strongly modulate not only the upper-layer circulation but also impact the deep flow.

scholarly journals The Flow through the Gulf of Mexico

2019 ◽  
Vol 49 (6) ◽  
pp. 1381-1401 ◽  
Author(s):  
J. Candela ◽  
J. Ochoa ◽  
J. Sheinbaum ◽  
M. López ◽  
P. Pérez-Brunius ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Straits Of Florida ◽  
The North ◽  
Astronomical Tide ◽  
Flow Through ◽  
Sverdrup Transport ◽  
The Mean ◽  
Yucatan Channel ◽  
Range Variation

AbstractFour years (September 2012 to August 2016) of simultaneous current observations across the Yucatan Channel (~21.5°N) and the Straits of Florida (~81°W) have permitted us to investigate the characteristics of the flow through the Gulf of Mexico. The average transport in both channels is 27.6 Sv (1 Sv = 106 m3 s−1), in accordance with previous estimates. At the Straits of Florida section, the transport related to the astronomical tide explains 55% of the observed variance with a mixed semidiurnal/diurnal character, while in the Yucatan Channel tides contribute 82% of the total variance and present a dominant diurnal character. At periods longer than a week the transports in the Yucatan and Florida sections have a correlation of 0.83 without any appreciable lag. The yearly running means of the transport time series in both channels are well correlated (0.98) and present a 3-Sv range variation in the 4 years analyzed. This long-term variability is well related to the convergence of the Sverdrup transport in the North Atlantic between 14.25° and 18.75°N. Using 2 years (July 2014–July 2016) of simultaneous currents observations in the Florida section, the Florida Cable section (~26.7°N), and a section across the Old Bahama Channel (~78.4°W), a mean northward transport of 28.4, 31.1, and 1.6 Sv, respectively, is obtained, implying that only 1.1 Sv is contributed by the Northwest Providence Channel to the mean transport observed at the Cable section during this 2-yr period.

The Subjective Present and Its Modulation in Clinical Contexts

2013 ◽  
Vol 1 (2) ◽  
pp. 239-259 ◽  
Author(s):  
Wolfgang Tschacher ◽  
Fabian Ramseyer ◽  
Claudia Bergomi
Keyword(s):  
Perceptual Grouping ◽  
Statistical Significance ◽  
Temporal Distribution ◽  
Future Research ◽  
Implicit Processes ◽  
The Social ◽  
Gestalt Perception ◽  
Psychotherapeutic Techniques ◽  
The Mean ◽  
The Individual

Time is a basic dimension in psychology, underlying behavior and experience. Timing and time perception constitute implicit processes that are often inaccessible to the individual person. Research in this field has shown that timing is involved in many areas of clinical significance. In the projects presented here, we combine timing with seemingly different fields of research, such as psychopathology, perceptual grouping, and embodied cognition. Focusing on the time scale of the subjective present, we report findings from three different clinical studies: (1) We studied perceived causality in schizophrenia patients, finding that perceptual grouping (‘binding’, ‘Gestalt formation’), which leads to visual causality perceptions, did not distinguish between patients and healthy controls. Patients however did integrate context (provided by the temporal distribution of auditory context stimuli) less into perceptions, in significant contrast to controls. This is consistent with reports of higher inaccuracy in schizophrenia patients’ temporal processing. (2) In a project on auditory Gestalt perception we investigated auditory perceptual grouping in schizophrenia patients. The mean dwell time was positively related to how much patients were prone to auditory hallucinations. Dwell times of auditory Gestalts may be regarded as operationalizations of the subjective present; findings thus suggested that patients with hallucinations had a shorter present. (3) The movement correlations of interacting individuals were used to study the non-verbal synchrony between therapist and patient in psychotherapy sessions. We operationalized the duration of an embodied ‘social present’ by the statistical significance of such associations, finding a window of roughly 5.7 seconds in conversing dyads. We discuss that temporal scales of nowness may be modifiable, e.g., by mindfulness. This yields promising goals for future research on timing in the clinical context: psychotherapeutic techniques may alter binding processes, hence the subjective present of individuals, and may affect the social present in therapeutic interactions.

scholarly journals Climate change and the occurrence of downy mildew in Brazilian grapevines

2017 ◽  
Vol 52 (6) ◽  
pp. 426-434 ◽  
Author(s):  
Francislene Angelotti ◽  
Emília Hamada ◽  
Edineide Elisa Magalhães ◽  
Raquel Ghini ◽  
Lucas da Ressureição Garrido ◽  
...  
Keyword(s):  
Climate Change ◽  
Latent Period ◽  
Downy Mildew ◽  
Temporal Distribution ◽  
Gas Emission ◽  
Grapevine Downy Mildew ◽  
Diseased Leaf Area ◽  
The Mean ◽  
Potential Impact ◽  
Logic Functions

Abstract: The objective of this work was to evaluate the potential impact of climate change on the occurrence of grapevine downy mildew in Brazil. Seedlings containing four to six leaves were sprayed with a sporangia suspension containing 105 sporangia per milliliter. After spraying, the seedlings were subjected to temperatures of 26, 28, 29.1, 30.4, and 31.8°C for 24 hours. The percentage of diseased leaf area and the latent period were evaluated. Maps of the geographic and temporal distribution of the disease were made considering the monthly average of the mean air temperature and leaf wetness duration for the reference climate or climate normal (1961-1990) and the future climates (2011-2040, 2041-2070, and 2071-2100), considering the A2 and B1 gas emission scenarios, designed by the Intergovernamental Panel on Climate Change (IPCC). Favorability ranges were set and used in logic functions of the geografical information system (GIS) to generate monthly maps for grapevine downy mildew. Rising temperatures interfered with the grapevine downy mildew infections, reduced the disease severity, and increased the latent period. Future climate scenarios indicate a reduction of favorability of downy mildew in Brazil, with variability in the different grape producing regions.

Spatiotemporal Spread of Potato virus S and Potato virus X in Seed Potato in Tasmania, Australia

2007 ◽  
Vol 8 (1) ◽  
pp. 70 ◽  
Author(s):  
Susan J. Lambert ◽  
Frank S. Hay ◽  
Sarah J. Pethybridge ◽  
Calum R. Wilson
Keyword(s):  
Seed Potato ◽  
Potato Virus ◽  
Temporal Distribution ◽  
Potato Virus X ◽  
Russet Burbank ◽  
Mechanical Transmission ◽  
Spatial And Temporal Distribution ◽  
Plant Spacing ◽  
Potato Virus S ◽  
The Mean

The spatial and temporal distribution of Potato virus S (PVS) and Potato virus X (PVX) was studied in two trials within each of four commercial fields of seed potato var. Russet Burbank in Tasmania, Australia. In the first trial (plots) 20 leaflets were collected from each of 49 plots (each approximately 8 m wide by 10 m long), with plots arranged in a 7-×-7 lattice. In the second trial (transects), leaflets were collected at 1-m intervals along seven adjacent, 50-m long rows. The mean incidence of PVS increased during the season by 5.2% in one of four plot trials and 25.5% in one of four transect trials. The mean incidence of PVX increased during the season by 10.1%, in one of two transect trials. Spatial Analysis by Distance IndicEs and ordinary runs analysis detected aggregation of PVS infected plants early in the season in one and two fields respectively, suggesting transmission during seed-cutting or during planting. An increase in PVS incidence mid- to late season in one field was associated with aggregation of PVS along, but not across rows, which may be related to the closer plant spacing within rows and hence increased potential for mechanical transmission along rows. Results suggested limited spread of PVS and PVX occurred within crops during the season. Accepted for publication 9 April 2007. Published 26 July 2007.

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