scholarly journals From 1/4° to 1/8°: Influence of Spatial Resolution on Eddy Detection Using Altimeter Data

2021 ◽  
Vol 14 (1) ◽  
pp. 149
Author(s):  
Yinuo Wang ◽  
Xiaoyan Chen ◽  
Guiyan Han ◽  
Pingping Jin ◽  
Jie Yang
Keyword(s):  
Mediterranean Sea ◽  
Spatial Resolution ◽  
Propagation Distance ◽  
Altimeter Data ◽  
The South ◽  
North West ◽  
Temporal Sampling ◽  
The North ◽  
The Mediterranean ◽  
Eddy Detection

A substantial portion of ocean eddies, especially small ones, may be missed due to insufficient spatial or temporal sampling by satellite altimetry. In order to illustrate the influence of spatial resolution on eddy detection, this study provides a comparison of eddy identification, tracking, and analysis between two sets of merged altimeter data with spatial resolutions of 1/4° and 1/8°. One main study area (the Mediterranean Sea), and three confirmatory areas (the South-China Sea, the North-West Pacific, and the South-East Pacific) are chosen. The results show that the number and density of eddies captured by the 1/8° data are about twice as much as those captured by the 1/4° data, while the ratios of corresponding eddy parameters, i.e., radius, amplitude, (eddy kinetic energy (EKE)) are about 0.6–0.8 (1.3) for the two datasets (1/8° ÷ 1/4°). Long-term eddy tracking (1993–2018) is conducted in the Mediterranean Sea, indicating that the improvement in spatial resolution will increase the observed values of both the lifetime and the propagation distance of robust eddies. The number of eddies identified using the 1/4° data only accounts for ~30% to 60% of those identified using the 1/8° data. However, for eddies that can be detected using the two datasets, ~5% to 10% present errors (i.e., confusion). In comparison between the four regions, we find that for the enclosed seas with complex conditions, the increase in spatial resolution may lead to more significant improvements in the efficiency and accuracy of eddy detection.

scholarly journals Time-clustering of wave storms in the Mediterranean Sea

2016 ◽  
Author(s):  
Giovanni Besio ◽  
Riccardo Briganti ◽  
Alessandro Romano ◽  
Lorenzo Mentaschi ◽  
Paolo De Girolamo
Keyword(s):  
Spatial Distribution ◽  
Mediterranean Sea ◽  
Time Scales ◽  
Horizontal Resolution ◽  
North West ◽  
Temporal Sampling ◽  
The North ◽  
Allan Factor ◽  
Long Time ◽  
The Mediterranean

Abstract. In this contribution we identify storm time-clustering in the Mediterranean Sea through the analysis of the spatial distribution of the Allan Factor. This parameter is evaluated from long time series of wave height provided by means of oceanographic buoy measurements and hindcast re-analysis spanning in the period 1979–2014 and characterized by a horizontal resolution of about 0.1 degree in longitude and latitude and a temporal sampling of one hour (Mentaschi et a., 2015). Results reveal clustering mainly for two distinct ranges of time scales. The first range of time scales (12 hrs to 50 days) is associated to sequences of storms generated by the persistence of the same meteorological system. The second range, associated to timescales beteween 50 and 100 days, reveals seasonal fluctuations. Transitional regimes are present at some locations in the basin. The spatial distribution of the Allan Factor reveals that the clustering at smaller time scales is present in the North-West of the Mediterranean, while clustering at larger scales is observed in the whole basin. This analysis is believed to be important to assess the local increased flood and coastal erosion risks due to storm clustering.

scholarly journals Time clustering of wave storms in the Mediterranean Sea

2017 ◽  
Vol 17 (3) ◽  
pp. 505-514 ◽  
Author(s):  
Giovanni Besio ◽  
Riccardo Briganti ◽  
Alessandro Romano ◽  
Lorenzo Mentaschi ◽  
Paolo De Girolamo
Keyword(s):  
Spatial Distribution ◽  
Mediterranean Sea ◽  
Horizontal Resolution ◽  
Comprehensive Analysis ◽  
North West ◽  
Temporal Sampling ◽  
The North ◽  
Allan Factor ◽  
Long Time ◽  
The Mediterranean

Abstract. In this contribution we identify storm time clustering in the Mediterranean Sea through a comprehensive analysis of the Allan factor. This parameter is evaluated from a long time series of wave height provided by oceanographic buoy measurements and hindcast reanalysis of the whole basin, spanning the period 1979–2014 and characterized by a horizontal resolution of about 0.1° in longitude and latitude and a temporal sampling of 1 h Mentaschi et al. (2015). The nature of the processes highlighted by the AF and the spatial distribution of the parameter are both investigated. Results reveal that the Allan factor follows different curves at two distinct timescales. The range of timescales between 12 h to 50 days is characterized by a departure from the Poisson distribution. For timescales above 50 days, a cyclic Poisson process is identified. The spatial distribution of the Allan factor reveals that the clustering at smaller timescales is present to the north-west of the Mediterranean, while seasonality is observed across the whole basin. This analysis is believed to be important for assessing the local increased flood and coastal erosion risks due to storm clustering.

Use of Numerical Wind-Wave Models for Assessment of the Offshore Wave Energy Resource

1997 ◽  
Vol 119 (3) ◽  
pp. 184-190 ◽  
Author(s):  
M. T. Pontes ◽  
S. Barstow ◽  
L. Bertotti ◽  
L. Cavaleri ◽  
H. Oliveira-Pires
Keyword(s):  
Mediterranean Sea ◽  
North Atlantic ◽  
Wave Energy ◽  
Wind Wave ◽  
Energy Resource ◽  
Altimeter Data ◽  
The North ◽  
The North Atlantic ◽  
The Mediterranean ◽  
Wave Models

In the last two decades the performance of numerical wind-wave models has improved considerably. Several models have been routinely producing good quality wave estimates globally since the mid-1980s. The verifications of wind-wave models have mainly focused on the evaluation of the error of the significant wave height Hs estimates. However, for wave energy purposes, the main parameters to be assessed are the wave power Pw and the mean (energy) period Te. Since Pw is proportional to Hs2 Tc, its expected error is much larger than for the single-wave parameters. This paper summarizes the intercomparison of two wind-wave models against buoy data in the North Atlantic and the Mediterranean Sea to select the most suitable one for the construction of an Atlas of the wave energy resource in European waters. A full verification in the two basins of the selected model—the WAM model implemented in the routine operation of the European Centre for Medium-Range Weather Forecasts—was then performed against buoy and satellite altimeter data. It was found that the WAM model accuracy is very good for offshore locations in the North Atlantic; but for the Mediterranean Sea the results are much less accurate, probably due to a lower quality of the input wind fields.

scholarly journals New Data on the Biology and Fisheries of the Threatened Palinurus elephas (Fabricius, 1787) (Decapoda, Achelata, Palinuridae) from the North-West Aegean Sea, Greece

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2390
Author(s):  
Thodoros E. Kampouris ◽  
Drosos Koutsoubas ◽  
Debora Milenkova ◽  
Georgios Economidis ◽  
Stylianos Tamvakidis ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Eastern Mediterranean ◽  
Spiny Lobster ◽  
Aegean Sea ◽  
North West ◽  
The North ◽  
Coastal Species ◽  
The Mediterranean ◽  
Species Specific ◽  
Palinurus Elephas

The European spiny lobster Palinurus elephas is a vulnerable species that inhabits and is harvested in the Mediterranean Sea and the adjacent Atlantic waters. The fisheries associated with the spiny lobster are mainly conducted with tangle nets, trammel nets, pots, and creels. The fishing pressure has greatly reduced their numbers, changing them from a common shallow coastal species to a largely remnant population. The relative research on the species’ biology and fisheries from the eastern Mediterranean Sea is almost absent. The fishery along the Chalkidiki Peninsula, Greece, is multispecies, and fishing is conducted by a small number of artisanal fishermen mainly using trammel nets. The lobster stock—both spiny and clawed lobsters—declined significantly during the late 1980s and early 1990s, later than most cases in the Mediterranean Sea. However, data regarding the nature and status of the fishery associated with the spiny lobster in Greece are lacking. Data regarding the characteristics of the spiny regional fishery were obtained by interviews and questionnaires. Additionally, fishery surveys were conducted during the main lobster fishing season from 1 May 2017 to 31 August 2017. Sixteen species were identified (15 finfish species and one invertebrate species) as targeted. In total, 79 spiny lobsters were sampled in this study; the population’s sex ratio significantly diverts from the theoretical 1:1 (χ2 = 4.57; p < 0.05), and males were dominant. Both male and female individuals demonstrate negative allometric growth profiles. In addition, no significant differences were observed between sexes. In Greece, thus far, the knowledge and information are sporadic, limited, and/or species-specific, most of which regard finfish fisheries. Furthermore, the national legislation is rather complicated—or too generalized—thus creating great uncertainties. The in-depth knowledge and experience of fishermen should be further acknowledged and utilized, and wider collaborations among scientists, practitioners, and policy-makers should be established. The present study poses some thoughts on the effectiveness of the recent EU Landing Obligation and its contribution to the potential restoration of the species.

scholarly journals First record of Dipolydora blakei (Annelida: Spionidae) from Europe: Greece, Mediterranean Sea

2013 ◽  
Vol 14 (1) ◽  
pp. 19 ◽  
Author(s):  
V. I. RADASHEVSKY ◽  
N. SIMBOURA
Keyword(s):  
New England ◽  
Mediterranean Sea ◽  
Coastal Waters ◽  
Aegean Sea ◽  
First Record ◽  
Ionian Sea ◽  
North West ◽  
The North ◽  
The Mediterranean ◽  
Of Greece

The spionid polychaete Dipolydora blakei is identified from benthic samples collected in the Aegean Sea off Chalkis and the Ionian Sea off Kalamitsi, both on the coast of Greece. Adults of D. blakei are characterized by having the falcate spines of chaetiger 5 with a large lateral tooth and bristles on the convex side of a long and pointed main fang, awl-like spines in posterior notopodia, branchiae beginning from chaetiger 7 and a pygidium with two lateral lobes. This is the first report of the species from the Mediterranean Sea and European waters and the second record (after one from Brazil) outside its type locality in deep-water off New England in the north-west Atlantic Ocean. The morphology of the Greek specimens is described and illustrated and diagnostic characters of the species are discussed. The origin of these specimens in the coastal waters of Greece is uncertain and the species is considered as cryptogenic in the Mediterranean Sea. An identification key to Dipolydora species with bristle-topped falcate spines in chaetiger 5 known from the Mediterranean Sea and European waters is provided.

Relationship Between Aromatic Hydrocarbons and Pelagic Tar in the Mediterranean Sea, 1974–75

1978 ◽  
Vol 5 (4) ◽  
pp. 295-297 ◽  
Author(s):  
Adam Zsolnay ◽  
Byron F. Morris ◽  
James N. Butler
Keyword(s):  
Aromatic Hydrocarbon ◽  
Mediterranean Sea ◽  
Aromatic Hydrocarbons ◽  
Sargasso Sea ◽  
The Baltic Sea ◽  
Detailed Report ◽  
North West ◽  
The North ◽  
The Mediterranean ◽  
The Baltic

During the winter of 1974–75, both tar and aromatic hydrocarbons were sampled in the Mediterranean Sea. A detailed report of the tar findings were given in a previous paper (Morris et al., 1975). Aromatic hydrocarbon concentrations at a depth of 1 m averaged 167 ng/1 (expressed as phenanthrene equivalents). This is only about 60% as great as the average aromatic hydrocarbon concentration found in the Baltic Sea, but is 5 times greater than what was found in the north-west Atlantic—including the Sargasso Sea (Zsolnay, 1977).No relationship was found between tar and aromatic hydrocarbon concentrations. This would indicate that the concentration of the latter is dependent upon other factors—such as the presence of other organic compounds that are capable of keeping the hydrophobic hydrocarbons in the water column by ‘solubilization.’

Depositional Environment Drive as Overpressure Generation: Study Case in “Gap” Field, North West Java Basin

2020 ◽  
Author(s):  
A., C. Prasetyo
Keyword(s):  
Clay Mineral ◽  
Depositional Environment ◽  
Mineral Content ◽  
Hydrocarbon Generation ◽  
Well Test ◽  
Burial History ◽  
The South ◽  
North West ◽  
The North ◽  
Geological Processes

Overpressure existence represents a geological hazard; therefore, an accurate pore pressure prediction is critical for well planning and drilling procedures, etc. Overpressure is a geological phenomenon usually generated by two mechanisms, loading (disequilibrium compaction) and unloading mechanisms (diagenesis and hydrocarbon generation) and they are all geological processes. This research was conducted based on analytical and descriptive methods integrated with well data including wireline log, laboratory test and well test data. This research was conducted based on quantitative estimate of pore pressures using the Eaton Method. The stages are determining shale intervals with GR logs, calculating vertical stress/overburden stress values, determining normal compaction trends, making cross plots of sonic logs against density logs, calculating geothermal gradients, analyzing hydrocarbon maturity, and calculating sedimentation rates with burial history. The research conducted an analysis method on the distribution of clay mineral composition to determine depositional environment and its relationship to overpressure. The wells include GAP-01, GAP-02, GAP-03, and GAP-04 which has an overpressure zone range at depth 8501-10988 ft. The pressure value within the 4 wells has a range between 4358-7451 Psi. Overpressure mechanism in the GAP field is caused by non-loading mechanism (clay mineral diagenesis and hydrocarbon maturation). Overpressure distribution is controlled by its stratigraphy. Therefore, it is possible overpressure is spread quite broadly, especially in the low morphology of the “GAP” Field. This relates to the delta depositional environment with thick shale. Based on clay minerals distribution, the northern part (GAP 02 & 03) has more clay mineral content compared to the south and this can be interpreted increasingly towards sea (low energy regime) and facies turned into pro-delta. Overpressure might be found shallower in the north than the south due to higher clay mineral content present to the north.

scholarly journals Impact of air–sea coupling on the climate change signal over the Iberian Peninsula

2021 ◽  
Author(s):  
Alba de la Vara ◽  
William Cabos ◽  
Dmitry V. Sein ◽  
Claas Teichmann ◽  
Daniela Jacob
Keyword(s):  
Climate Change ◽  
Iberian Peninsula ◽  
Mediterranean Sea ◽  
Large Scale ◽  
Regional Distribution ◽  
Coupled Model ◽  
Climate Change Signal ◽  
The North ◽  
The Mediterranean ◽  
The Impact

AbstractIn this work we use a regional atmosphere–ocean coupled model (RAOCM) and its stand-alone atmospheric component to gain insight into the impact of atmosphere–ocean coupling on the climate change signal over the Iberian Peninsula (IP). The IP climate is influenced by both the Atlantic Ocean and the Mediterranean sea. Complex interactions with the orography take place there and high-resolution models are required to realistically reproduce its current and future climate. We find that under the RCP8.5 scenario, the generalized 2-m air temperature (T2M) increase by the end of the twenty-first century (2070–2099) in the atmospheric-only simulation is tempered by the coupling. The impact of coupling is specially seen in summer, when the warming is stronger. Precipitation shows regionally-dependent changes in winter, whilst a drier climate is found in summer. The coupling generally reduces the magnitude of the changes. Differences in T2M and precipitation between the coupled and uncoupled simulations are caused by changes in the Atlantic large-scale circulation and in the Mediterranean Sea. Additionally, the differences in projected changes of T2M and precipitation with the RAOCM under the RCP8.5 and RCP4.5 scenarios are tackled. Results show that in winter and summer T2M increases less and precipitation changes are of a smaller magnitude with the RCP4.5. Whilst in summer changes present a similar regional distribution in both runs, in winter there are some differences in the NW of the IP due to differences in the North Atlantic circulation. The differences in the climate change signal from the RAOCM and the driving Global Coupled Model show that regionalization has an effect in terms of higher resolution over the land and ocean.

A gold diadem from Aegina

1987 ◽  
Vol 107 ◽  
pp. 182-182
Author(s):  
Reynold Higgins
Keyword(s):  
Bronze Age ◽  
British Museum ◽  
The South ◽  
North West ◽  
The North ◽  
The Dead ◽  
Middle Helladic ◽  
Dead Man ◽  
The Bronze Age ◽  
Grave Goods

A recent discovery on the island of Aegina by Professor H. Walter (University of Salzburg) throws a new light on the origins of the so-called Aegina Treasure in the British Museum.In 1982 the Austrians were excavating the Bronze Age settlement on Cape Kolonna, to the north-west of Aegina town. Immediately to the east of the ruined Temple of Apollo, and close to the South Gate of the prehistoric Lower Town, they found an unrobbed shaft grave containing the burial of a warrior. The gravegoods (now exhibited in the splendid new Museum on the Kolonna site) included a bronze sword with a gold and ivory hilt, three bronze daggers, one with gold fittings, a bronze spear-head, arrowheads of obsidian, boar's tusks from a helmet, and fragments of a gold diadem (plate Va). The grave also contained Middle Minoan, Middle Cycladic, and Middle Helladic (Mattpainted) pottery. The pottery and the location of the grave in association with the ‘Ninth City’ combine to give a date for the burial of about 1700 BC; and the richness of the grave-goods would suggest that the dead man was a king.

Part VI. The Cyclopean Terrace Building and the Deposit of Pottery beneath It

1954 ◽  
Vol 49 ◽  
pp. 267-291
Author(s):  
Elizabeth B. Wace
Keyword(s):  
Contour Line ◽  
The South ◽  
Main Road ◽  
North West ◽  
North East ◽  
The North ◽  
South West

The Cyclopean Terrace Building lies to the north-west of the Lion Gate on the northern end of the Panagia Ridge and faces almost due west across the valley of the Kephissos and modern main road from Corinth to Argos. It lies just below the 200 m. contour line, and one terrace below the houses excavated in 1950–51 by Dr. Papadimitriou and Mr. Petsas to the east at the same end of the ridge. The area contains a complex of buildings, both successive and contemporary, and in view of the discovery of structures both to the south-west and, by the Greek Archaeological Service, to the north-east it is likely that this whole slope was covered by a portion of the outer town of Mycenae. This report will deal only with the structure to which the name Cyclopean Terrace Building was originally given, the so-called ‘North Megaron’, supported by the heavy main terrace wall.The excavation of this structure was begun in 1923. The main terrace wall was cleared and two L.H. IIIC burials discovered in the top of the fill in the south room. In 1950 it was decided to attempt to clear this building entirely in an endeavour to find out its date and purpose. The clearing was not, however, substantially completed until the close of the 1953 excavation season, and this report presents the available evidence for the date as determined by the pottery found beneath the building; the purpose is still a matter for study, though various tentative conclusions can be put forward.

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