Pattern evolution and interactions in subaqueous dune fields: North Loup River, Nebraska, U.S.A.

2020 ◽  
Vol 90 (12) ◽  
pp. 1734-1746
Author(s):  
Jasmine Mason ◽  
Benjamin T. Cardenas ◽  
Mackenzie D. Day ◽  
Max Daniller-Varghese ◽  
Sarah C. Brothers ◽  
...  
Keyword(s):  
Procrustes Analysis ◽  
Aerial Images ◽  
Spatial Density ◽  
Ambient Fluid ◽  
Interaction Type ◽  
Dune Field ◽  
The North ◽  
Aeolian Dunes ◽  
The Mean ◽  
Pattern Variability

ABSTRACT A time series of aerial images of a dune field on a migrating free bar in the North Loup River, Nebraska, is used to generate a quantified dataset that allows analyses of crestline deformation, dune interaction type and spatial density, and impact of spurs. Measurement of dune parameters show that the dune field maintained a dynamic steady-state pattern, despite high rates of deformation, common interactions, and sediment bypassing. Mapped crestlines had a mean migration rate of 8 cm/min. The mean deformation rate, quantified using a partial Procrustes analysis, was 2 cm/min, indicating that along individual crestlines, local migration varied ± 25% from the bedform mean. Dune interactions caused the break-apart and recombination of crestline segments, thus limiting pattern variability caused by deformation. Although most of the 50 documented interactions are comparable to those observed in aeolian dune fields, defect-driven interactions are less common and interactions caused by migration of the convex-downstream nose of the dunes were observed, which has not been reported in aeolian dunes. The spatial density of interactions is consistent with that derived for aeolian crescentic-dune fields, in spite of differences in ambient fluid and dune size. Although spurs were ubiquitous, their presence did not have a quantifiable impact on deformation and interactions as compared to areas where spurs were absent, suggesting that these short-lived features affect instantaneous flux rates only.

scholarly journals A cloud-to-ground lightning climatology for north-eastern Italy

2013 ◽  
Vol 10 (1) ◽  
pp. 77-84 ◽  
Author(s):  
L. Feudale ◽  
A. Manzato ◽  
S. Micheletti
Keyword(s):  
Spatial Distribution ◽  
Eastern Alps ◽  
Spatial Density ◽  
North East ◽  
The North ◽  
Lightning Detection ◽  
North Eastern ◽  
Cloud To Ground Lightning ◽  
The Mean ◽  
Southern Flank

Abstract. This study analyzes the spatial distribution and temporal characteristics of cloud-to-ground lightnings (C2G) in the North East of Italy and the neighboring areas of Austria, Slovenia and Croatia. The dataset consists of about 6.5 millions C2G flash records, both positive and negative, observed between January 1995 and December 2011 by the "Centro Elettrotecnico Sperimentale Italiano-Sistema Italiano Rilevamento Fulmini'' (CESI/SIRF), part of the European Cooperation for Lightning Detection (EUCLID) Network. The results show that C2G lightnings concentrate in the foothill regions on the southern flank of the Eastern Alps with a maximum of discharge frequency of 10 lightnings per km2 per year. The number of C2G strokes varies with the period of the year: the most active period for lightning starts in April and lasts through November with the highest number of C2G strokes happening during the summer months of July and August, with maximum spatial density slightly moving from the mountain to the coastal area. The least frequency of C2G strokes is observed during wintertime. The mean diurnal C2G lightning activity for the whole domain shows a peak around 16:00–17:00 UTC and reaches a minimum around 07:00–09:00 UTC; the mean spatial distribution follows different patterns depending on the period of the day.

Subglacial topography and thickness of ice caps on the Argentine Islands

2019 ◽  
Vol 31 (6) ◽  
pp. 332-344 ◽  
Author(s):  
Jānis Karušs ◽  
Kristaps Lamsters ◽  
Anatolii Chernov ◽  
Māris Krievāns ◽  
Jurijs Ješkins
Keyword(s):  
Land Surface ◽  
Geological Structure ◽  
Aerial Images ◽  
Ice Thickness ◽  
Ice Caps ◽  
The North ◽  
Prevailing Wind Direction ◽  
Aerial Vehicle ◽  
Subglacial Topography ◽  
Ground Penetrating

AbstractThis study presents the first subglacial topography and ice thickness models of the largest ice caps of the Argentine Islands, Wilhelm Archipelago, West Antarctica. During this study, ground-penetrating radar was used to map the thickness and inner structure of the ice caps. Digital surface models of all studied islands were created from aerial images obtained with a small-sized unmanned aerial vehicle and used for the construction of subglacial topography models. Ice caps of the Argentine Islands cover ~50% of the land surface of the islands on average. The maximum thickness of only two islands (Galindez and Skua) exceeds 30 m, while the average thickness of all islands is only ~5 m. The maximum ice thickness reaches 35.3 m on Galindez Island. The ice thickness and glacier distribution are mainly governed by prevailing wind direction from the north. This has created the prominent narrow ice ridges on Uruguay and Irizar islands, which are not supported by topographic obstacles, as well as the elongated shape of other ice caps. The subglacial topography of the ice caps is undulated and mainly dependent on the geological structure and composition of magmatic rocks.

Lake and inland dunes as interconnected Systems: The story of Lake Tresssee and an adjacent dune field (Schleswig-Holstein, North Germany)

The Holocene ◽  
2020 ◽  
pp. 095968362098168
Author(s):  
Christian Stolz ◽  
Magdalena Suchora ◽  
Irena A Pidek ◽  
Alexander Fülling
Keyword(s):  
Water Level ◽  
Bronze Age ◽  
Environmental Changes ◽  
High Water ◽  
Alluvial Fan ◽  
Water Levels ◽  
Lake Area ◽  
Dune Field ◽  
The North ◽  
Sand Drift

The specific aim of the study was to investigate how four adjacent geomorphological systems – a lake, a dune field, a small alluvial fan and a slope system – responded to the same impacts. Lake Tresssee is a shallow lake in the North of Germany (Schleswig-Holstein). During the Holocene, the lake’s water surface declined drastically, predominately as a consequence of human impact. The adjacent inland dune field shows several traces of former sand drift events. Using 30 new radiocarbon ages and the results of 16 OSL samples, this study aims to create a new timeline tracing the interaction between lake and dunes, as well, as how both the lake and the dunes reacted to environmental changes. The water level of the lake is presumed to have peaked during the period before the Younger Dryas (YD; start at 10.73 ka BC). After the Boreal period (OSL age 8050 ± 690 BC) the level must have undergone fluctuations triggered by climatic events and the first human influences. The last demonstrable high water level was during the Late Bronze Age (1003–844 cal. BC). The first to the 9th century AD saw slightly shrinking water levels, and more significant ones thereafter. In the 19th century, the lake area was artificially reduced to a minimum by the human population. In the dunes, a total of seven different phases of sand drift were demonstrated for the last 13,000 years. It is one of the most precisely dated inland-dune chronologies of Central Europe. The small alluvial fan took shape mainly between the 13th and 17th centuries AD. After 1700 cal. BC (Middle Bronze Age), and again during the sixth and seventh centuries AD, we find enhanced slope activity with the formation of Holocene colluvia.

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.

Bankarization in the first European cities with an equal number of Muslim and Christian inhabitants

2017 ◽  
Vol 10 (4) ◽  
pp. 554-580
Author(s):  
Miguel Ángel Pérez-Castro ◽  
Miguel Ángel Montero-Alonso ◽  
Akram Abderrahman-Azaar
Keyword(s):  
North Coast ◽  
Content Type ◽  
European Cities ◽  
The North ◽  
Financial Depth ◽  
Financial Framework ◽  
European Banks ◽  
The Mean ◽  
Different Cultures ◽  
Near Future

Purpose This paper aims to analyze the situation of the financial system in the Spanish-governed cities of Melilla and Ceuta, Christian and Muslim cities located on the north coast of Africa, and compared it with the mean bankarization level in the rest of Spain in 2000-2015. Design/methodology/approach Although different calculation methods have been proposed, most authors agree that the bankarization level of a country or a territory reflects the development of the society as a whole and has a positive correlation with economic growth. The indicators of financial depth proposed by these researchers are not only the ratio between variables such as loans, deposits, etc., but also the ratios of these variables to the population and the gross domestic product (GDP) of the country or territory. Findings The results obtained revealed that there are differences between these two North African Spanish cities. Furthermore, the financing gap between the mean bankarization levels of these cities and those of mainland Spain was found to be even larger than most of the other economic indicators (GDP per capita and the unemployment rate). Practical implications The authors are convinced that the manuscript is a contribution of great interest for serving pilot experience in cities wishing to offer a development of traditional banking and Islamic banking. The paper should be of interest to readers in the areas of finance systems and commercial banks where two different cultures coexist. Originality/value This is the first research study on the financial framework of European cities whose populations have an approximately equal percentage of Christians and Muslims. The data reflected the existence of savings and loan methods parallel to conventional banking. The conclusion was that in the near future, it would be advisable for European banks to take into account the cultural customs and religious practices of potential Muslim clients.

scholarly journals On tho proportions of the prevailing winds, the mean temperature, and depth of rain in the climate of London, computed through a cycle of Eighteen Years, or periods of the Moon’s declination

1843 ◽  
Vol 4 ◽  
pp. 300-300
Keyword(s):  
The Moon ◽  
Fair Weather ◽  
North West ◽  
West Wind ◽  
North East ◽  
East Wind ◽  
The North ◽  
The Common ◽  
The Mean ◽  
Solar Influence

In this paper the author investigates the periodical variations of the winds, rain and temperature, corresponding to the conditions of the moon’s declination, in a manner similar to that he has already followed in the case of the barometrical variations, on a period of years extending from 1815 to 1832 inclusive. In each case he gives tables of the average quantities for each week, at the middle of which the moon is in the equator, or else has either attained its maximum north or south declination. He thus finds that a north-east wind is most promoted by the constant solar influence which causes it, when the moon is about the equator, going from north to south; that a south-east wind, in like manner, prevails most when the moon is proceeding to acquire a southern declination ; that winds from the south and west blow more when the moon is in her mean degrees of declination, going either way, than with a full north or south declination ; and that a north-west wind, the common summer and fair weather wind of the climate, affects, in like manner, the mean declination, in either direction, in preference to the north or south, and most when the moon is coming north. He finds the average annual depth of rain, falling in the neighbourhood of London, is 25’17 inches.

PREDATION BY INSECTS AND SPIDERS INHABITING COLONIAL WEBS OF HYPHANTRIA CUNEA

1972 ◽  
Vol 104 (8) ◽  
pp. 1197-1207 ◽  
Author(s):  
R. F. Morris
Keyword(s):  
Population Dynamics ◽  
Nova Scotia ◽  
North America ◽  
Population Density ◽  
New Brunswick ◽  
Numerical Response ◽  
Initial Number ◽  
Hyphantria Cunea ◽  
The North ◽  
The Mean

AbstractThe number of predators inhabiting nests of Hyphantria cunea Drury was recorded annually for 13 years in four areas in New Brunswick and two areas on the coast of Nova Scotia. The most common groups were the pentatomids and spiders, which sometimes reproduced within the nests, but the mean number per nest was low in relation to the number of H. cunea larvae in the colonies. The rate of predation on fifth-instar larvae was low. Small or timid predators appeared to prey largely on moribund larvae or small saprophagans during the principal defoliating instars of H. cunea.No relationship could be detected between the number of larvae reaching the fifth instar and the number of predators in the colony; nor could any functional or numerical response of the predators to either the initial number of larvae per colony or the population density of colonies be found. It is concluded that the influence of the nest-inhabiting predators is small and relatively stable, and may be treated as a constant in the development of models to explain the population dynamics of H. cunea.H. cunea is a pest in parts of Europe and Asia, where it has been accidentally introduced from North America. The introduction to other continents of the North American predator, Podisus maculiventiis (Say), is discussed briefly.

scholarly journals Different trends between extreme and median surface aerosol extinction coefficients over China inferred from quality controlled visibility data

2017 ◽  
Author(s):  
Jing Li ◽  
Chengcai Li ◽  
Chunsheng Zhao
Keyword(s):  
Northwest China ◽  
Positive Trend ◽  
Median Surface ◽  
Aerosol Extinction ◽  
Significance Level ◽  
The North ◽  
Synoptic Conditions ◽  
The Mean ◽  
Mean Trend ◽  
Year 2000

Abstract. Although the temporal changes of aerosol properties have been widely investigated, the majority focused on the averaged condition without much emphasis on the extremes. However, the latter can be more important in terms of human health and climate change. This study uses a previously validated, quality-controlled visibility dataset to investigate the long-term trends of extreme surface aerosol extinction coefficient (AEC) over China, and compare them with the median trends. Two methods are used to independently evaluate the trends, which arrive at consistent results. The sign of extreme and median trends are generally coherent, whereas their magnitudes show distinct spatial and temporal differences. In the 1980s, an overall positive trend is found throughout China with the extreme trend exceeding the mean trend, except for Northwest China and the North China Plain. In the 1990s, AEC over Northeast and Northwest China starts to decline while the rest of the country still exhibits an increase. The extreme trends continue to dominate in the south while it yields to the mean trend in the north. After year 2000, the extreme trend becomes weaker than the mean trend overall in terms of both the magnitude and significance level. The annual trend can be primarily attributed to winter and fall trends. The results suggest that the decadal changes of pollution in China may be governed by different mechanisms. Synoptic conditions that often result in extreme air quality changes might dominate in the 1980s, whereas emission increase might be the main factor for the 2000s.

scholarly journals Simulated Relationships between Regional Temperatures and Large-Scale Circulation: 125 kyr BP (Eemian) and the Preindustrial Period

2005 ◽  
Vol 18 (19) ◽  
pp. 4032-4045 ◽  
Author(s):  
Nikolaus Groll ◽  
Martin Widmann ◽  
Julie M. Jones ◽  
Frank Kaspar ◽  
Stephan J. Lorenz
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Temperature Sensitive ◽  
Proxy Data ◽  
Large Scale Circulation ◽  
The North ◽  
Temperature Signal ◽  
Northern Winter ◽  
The Mean ◽  
Mean Circulation

Abstract To investigate relationships between large-scale circulation and regional-scale temperatures during the last (Eemian) interglacial, a simulation with a general circulation model (GCM) under orbital forcing conditions of 125 kyr BP is compared with a simulation forced with the Late Holocene preindustrial conditions. Consistent with previous GCM simulations for the Eemian, higher northern summer 2-m temperatures are found, which are directly related to the different insolation. Differences in the mean circulation are evident such as, for instance, stronger northern winter westerlies toward Europe, which are associated with warmer temperatures in central and northeastern Europe in the Eemian simulation, while the circulation variability, analyzed by means of a principal component analysis of the sea level pressure (SLP) field, is very similar in both periods. As a consequence of the differences in the mean circulation the simulated Arctic Oscillation (AO) temperature signal in the northern winter, on interannual-to-multidecadal time scales, is weaker during the Eemian than today over large parts of the Northern Hemisphere. Correlations between the AO index and the central European temperature (CET) decrease by about 0.2. The winter and spring SLP anomalies over the North Atlantic/European domain that are most strongly linearly linked to the CET cover a smaller area and are shifted westward over the North Atlantic during the Eemian. However, the strength of the connection between CET and these SLP anomalies is similar in both simulations. The simulated differences in the AO temperature signal and in the SLP anomaly, which is linearly linked to the CET, suggest that during the Eemian the link between the large-scale circulation and temperature-sensitive proxy data from Europe may differ from present-day conditions and that this difference should be taken into account when inferring large-scale climate from temperature-sensitive proxy data.

scholarly journals Energetic Submesoscales Maintain Strong Mixed Layer Stratification during an Autumn Storm

2017 ◽  
Vol 47 (10) ◽  
pp. 2419-2427 ◽  
Author(s):  
Daniel B. Whitt ◽  
John R. Taylor
Keyword(s):  
Mixed Layer ◽  
North Atlantic ◽  
Small Scale ◽  
Upper Ocean ◽  
Ocean Mixed Layer ◽  
Ocean Stratification ◽  
The North ◽  
Large Eddy ◽  
The Mean ◽  
Scale Turbulence

AbstractAtmospheric storms are an important driver of changes in upper-ocean stratification and small-scale (1–100 m) turbulence. Yet, the modifying effects of submesoscale (0.1–10 km) motions in the ocean mixed layer on stratification and small-scale turbulence during a storm are not well understood. Here, large-eddy simulations are used to study the coupled response of submesoscale and small-scale turbulence to the passage of an idealized autumn storm, with a wind stress representative of a storm observed in the North Atlantic above the Porcupine Abyssal Plain. Because of a relatively shallow mixed layer and a strong downfront wind, existing scaling theory predicts that submesoscales should be unable to restratify the mixed layer during the storm. In contrast, the simulations reveal a persistent and strong mean stratification in the mixed layer both during and after the storm. In addition, the mean dissipation rate remains elevated throughout the mixed layer during the storm, despite the strong mean stratification. These results are attributed to strong spatial variability in stratification and small-scale turbulence at the submesoscale and have important implications for sampling and modeling submesoscales and their effects on stratification and turbulence in the upper ocean.

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