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Diet variability in Eurasian perch (Perca fluviatilis) as a response to environmental variables along a latitudinal gradientBublys, Kasparas January 2018 (has links)
Climate change is expected to have a profound impact on freshwater fish communities, especially at higher latitudes. In this study I investigated potential effects of climate change on the niche structure of Eurasian perch (Perca fluviatilis) by looking at their diet across a latitudinal gradient and at varying light climate. Dietary niche width of Eurasian perch did not differ significantly between boreal and temperate latitudes. Additionally, no significant difference in the prevalence of specialist individuals was found along the latitudinal gradient and water transparency levels. Habitat was the main factor that significantly affected niche width and level of specialization with both being significantly higher in the littoral habitat. Taken together my results suggest that climate change might indirectly affect niche patterns by altering fish densities through changes in productivity resulting in niche and specialization variation among habitats.
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Análise e comparaçao dos resultados de observaçoes obtidas com teodolitos Wild T-2 e T-4 para determinaçao da latitude astronômica de segunda ordemCampos, Milton de Azevedo, Hatschbach, Fernando January 1979 (has links)
Resumos em portugues e ingles / Orientador: Fernando Hatschbach / Dissertaçao (mestrado) -Universidade Federal do Paraná. Curso de Pós-Graduaçao em Ciencias Geodésicas / Resumo: Esta dissertação trata da comparação e analise dos resultados obtidos em determinações, a nível de segunda ordem, realizadas com equipamentos específicos para observações de 2ª ordem (teodolito com leitura direta de 1") e específicos para observações de 1ª ordem (teodolito com leitura direta de 0,1"), procurando verificar se há ou não conveniência em se utilizar equipamento mais sofisticado do que o necessário, quando se dispõe de toda a gama de teodolitos, em determinações com precisão adrede estabelecida. O autor pretendia, a princípio, realizar observações para a determinação do meridiano astronômico (pelo método de Estrelas Próximas ou em Elongação), da hora local (pelo método de Zinger) e da latitude astronômica (pelo método de Horrebow-Talcott simplificado, conhecido no Brasil por método de Sterneck), porém, devido às condições atmosféricas adversas em Curitiba (dez noites úteis em cento e um dias), restringiu as observações somente para a determinação da latitude astronômica. / Abstract: This essay deals with the comparison and analysis of results obtained in second order accuracy determinations, acomplished with equipment specifically for second order observations (theodolites with 1" direct-reading) and specifically for first order observations (theodolites with 0,1" direct-reading) in an attempt to verify if it is warranted to use more sophisticated equipment than necessary when one has at his disposal a complete range of theodolites in pre-determined settings. The author initially had in mind to carry out observations for the determination of the astronomic meridian (by the Stars near or at elongations method), of the civil time (by Zinger method), and of the astronomic latitude (by the simplified Horrebow-Talcott method, known in Brazil as the Sterneck method). However, due to the adverse atmospheric conditions in Curitiba (10 useful nights in one hundred and one days), he has restricted his observations only to the determination of the astronomic latitude.
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Climatology of Middle and Low-Latitude F-Region Plasma Drifts from Satellite MeasurementsJensen, John W. 01 May 2007 (has links)
We used ion drift observations from the DE-2 satellite to study for the first time the longitudinal variations of middle and low latitude F-region zonal plasma drifts during quiet and disturbed conditions. The daytime quiet-time drifts do not change much with longitude. In the dusk-premidnight period, the equinoctial middle latitude westward drifts are smallest in the European sector, and the low latitude eastward drifts are largest in the American-Pacific sector. The longitudinal variations of the late night-early morning drifts during June and December solstice are anti-correlated. During geomagnetically active time s, there are large westward perturbation drifts in the late afternoon-early night sector at upper middle latitudes and in the midnight sector at low latitudes. The largest westward disturbed drifts during equinox occur in the European sector and the smallest in the Pacific region. These results suggest that during equinox, Subauroral Polarization Streams (SAPS) events occur most often at European longitudes. The low latitude perturbation drifts do not show significant longitudinal dependence.
We have used five years of measurements on board the ROCSA T-1 satellite to develop a detailed local-time, season, and longitude-dependent quiet-time global empirical model for equatorial F-region vertical plasma drifts. We show that the longitudinal dependence of the daytime and nighttime vertical drifts is much stronger than reported earlier, especially during December and June solstice. The late night downward drift velocities are larger in the eastern than in the western hemisphere at all seasons, the morning and afternoon December solstice drifts have significantly different longitudinal dependence, and the daytime upward drifts have strong wavenumber-four signatures during equinox and June solstice. The largest evening upward drifts occur during equinox and December solstice near the American sector. The longitudinal variations of the evening prereversal velocity peaks during December and June solstice are anti-correlated, which further indicates the importance of conductivity effects on the electrodynamics of the equatorial ionosphere. We have shown that disturbance dynamo largely does not affect daytime drifts. The upward perturbations during the nighttime are largely season independent, but near the prereversal enhancement, the downward perturbation drifts are largest during equinox and smallest during December.
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An Evaporation Model for High Latitude Upland Lichen SurfacesStewart, Robert Bruce 05 1900 (has links)
<p> Energy-budget calculations and equilibrium model estimates of evaporation from a lichen-dominated upland site in the Hudson Bay low-lands are presented. The energy budget calculations reveal that the lichen surface is relatively resistant to evaporation with an average of only 54 percent of the daily net radiation being utilized in the evaporative process. Equilibrium estimates of evaporation consistently overestimate actual evaporation by 5 and 8 percent for hourly values and daily totals respectively. A simple model, a function of the equilibrium model, is derived from a comparison of actual and equilibrium evaporation. The
only inputs required for the model are net radiation, soil heat flow and screen temperatures. Tests of the model indicate that it will predict actual evaporation within 5 percent and that it can probably be applied to any high latitude surface which exhibits a relatively large resistance to evaporation.</p> / Thesis / Master of Science (MSc)
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High Latitude Ionospheric Scintillation CharacterizationJiao, Yu 20 August 2013 (has links)
No description available.
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Changing Depositional Environments in the Marginal Zone of a High Latitude Ice SheetMiller, Raoul 08 1900 (has links)
This thesis is missing page 28 from this and all other copies. -Digitization Centre / Glacial and glacially-influenced deposits examined at two sites in west-central Ellesmere Island provide insights into the nature of glaciation during the late-Wisconsinan and Holocene advances, and the modes of deposition from arid, high latitude ice bodies. Glacial lithofacies identified indicate that englacial debris content varied spatially and it is inferred that basal thermal conditions also exhibited a complex pattern. Direct glacial deposits usually consist of unsorted diamicts with a complete size range of matrix components, indicating an absence of meltwater-sorting or winnowing during deposition. Glacially-influenced fluvial, lacustrine, and nearshore marine deposits show that most of the Quaternary sediments were deposited by low-frequency, high magnitude events during deglaciation. A tentative reconstruction of late-glacial history in the Strathcona Fiord area proposes that an ice tongue surged down Strathcona Fiord from a previous maximum position coincident with the present day head of the fiord. This surge destabilised the margin locally, causing rapid collapse in the valleys and melting into ice-cored basins on the higher plateau areas. Periodically these ice-cored basins would drain, providing large water and sediment discharges and reworking in some sites whilst leaving other deposits unaffected. Subsequent reworking has been minimal in the cold, arid environment where continued uplift favours fluvial incision rather than extensive sandur development.
Examination of the modern ice margin shows that the ice here is frozen to the substrate but basal debris bands indicate that at some localities basal temperatures must be above pressure melting point. Patterns of debris entrainment and deposition and debris lithologies suggest that much of the transported debris is incorporated where lobes of ice begin to flow out from the main ice cap. / Thesis / Master of Science (MS)
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Contemporary Ionospheric Scintillation Studies: Statistics, 2D Analytical and 3D Numerical InversionConroy, James Patrick 31 August 2022 (has links)
The propagation of radiowaves through ionospheric irregularities can lead to random amplitude and phase fluctuations of the signal, otherwise known as scintillation, which can severely impact the performance of Global Navigation Satellite System (GNSS) and communication systems. Research into high latitude scintillation, through statistical analysis and inverse modeling, was completed to provide insight into the temporal and spatial distribution, and irregularity parameters, which can ultimately support the development of impact mitigation techniques, and deepen our understanding of the underlying physics. The work in this dissertation focused on the statistical analysis of Global Positioning System (GPS) scintillation data, data inversion, two-dimensional (2D) and three-dimensional (3D) scintillation modeling. The statistical analysis revealed distinct trends in the distribution of scintillation, while demonstrating that for GPS signals, phase scintillation occurs most frequently and can be treated as stochastic Total Electron Content (TEC); findings which have significant implications for impact mitigation. For the first of two inversion studies, scintillation data associated with a series of Polar Cap Patches (PCPs), which are common large-scale high latitude structures, was inverted to gain insight into the composition of the underlying irregularities.
The results of this study suggest that the irregularities can be modeled as rods interbedded with sheets, which is knowledge that is crucial for the anchoring of models used to develop system mitigation techniques. The final study presents the results of modeling and inversion work to identify the conditions under which a 2D analytic version of the 3D numerical Satellite-beacon Ionospheric-scintillation global model of the upper atmosphere (SIGMA) model can be used to perform modeling in high latitude regions. During the study, it was found that the analytic model tends to diverge for electron density variance times irregularity layer thickness values exceeding 2, matched reasonably well for correlation length to thickness ratios up to 0.2, and was incompatible when ratios approached 0.35. An elevation angle limitation was also identified for the 2D model, and inflated values for the electron density variance were observed overall, which are thought to result from the weak scatter limits of the analytic model. These inflated values were particularly acute in the auroral zone during elevated conditions and suggest that the analytic model used in the study is not well suited for modeling the highly elongated irregularities associated with auroral precipitation. / Doctor of Philosophy / The ionosphere is a region of the earth's atmosphere extending from approximately 90 to 1000 km in altitude. Radio wave signals which travel through irregularities in the ionosphere can be distorted in a way that can lead to random amplitude and phase fluctuations of the signal, otherwise known as scintillation, which can severely degrade the performance of navigation and communication systems. Research into high latitude scintillation, through statistical analysis, and data and model matching, was completed to provide insight into the time and space distribution, and irregularity parameters, in order to ultimately deepen our understanding of the physics and to help develop better models. The work in this dissertation focused on the statistical analysis of GPS scintillation data, data and model matching, and 2D and 3D irregularity modeling. The statistical analysis revealed distinct trends in the distribution of scintillation, while demonstrating that for GPS signals, phase scintillation occurs most frequently but the impacts can be corrected if measured; findings which have significant implications for impact mitigation. For the first of two model and data matching studies, scintillation data associated with a series of common large-scale high latitude structures called PCPs, was matched to a model to gain insight into the composition of the underlying irregularities. The results of this study suggest that the irregularities can be modeled as vertical rods oriented along the magnetic field interbedded within flat sheets, which is knowledge that is crucial for having confidence in the models used to develop system mitigation techniques. The final study presents the results of modeling and data matching work to identify the conditions under which a 2D or 3D model can be used to perform irregularity modeling in the high latitude regions. During the study, it was found that the 2D model tends to diverge from the 3D model for significant variations in the ionosphere, and when irregularity rods are highly elongated. A signal propagation path elevation angle limitation was also identified for the 2D model, and inflated values for the predicted ionospheric variations were observed overall, which are thought to result from limits of the 2D model compared to the more general 3D version. These inflated values were particularly acute in the auroral region during elevated conditions and suggest that the 2D model used in the study is not well suited for modeling the highly elongated irregularities associated with aurora effects.
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SENSIBILIDADE ÀS PARAMETRIZAÇÕES FÍSICAS DO WRF NAS PREVISÕES DOS PARÂMETROS ATMOSFÉRICOS EM SHETLAND DO SUL E DECEPTION / WRF SENSITIVITY TO THE PHYSICAL PARAMETERIZATIONS IN THE FORECASTS OF ATMOSPHERIC PARAMETERS AT THE SOUTH SHETLAND AND DECEPTIONComin, Alcimoni Nelci 05 February 2013 (has links)
The Weather Research and Forecasting model (WRF) was executed with high resolution and
three nested grids of 12 km, 3 km and 1 km in the South Shetland and particularly in
Deception Island s bay, during the period from 5 to 23 February 2011 at Operation Antarctica
29. Data were obtained in situ by Polar Ship Almirante Maximiano from Brazilian Navy, with
a frequency of 1 h. The measured variables are pressure, temperature, dew point temperature,
wind speed and direction. The model lateral and boundary conditions were data from NCEP
global model, with a horizontal resolution of 1o and updated every 6 hours. Two domain sizes
have been tested for the innermost grid, one with 127 and the other with 187 points in each
horizontal direction. Besides, two physical configurations have been tested, with the main
differences being snow microphysics and soil thermal diffusion. Pressure was the variable
best represented by the model, as it is the most dependent on large scale meteorological
patterns having only small dependence on the microscale. The wind direction and speed at 10
meters from the surface were also accurate, except when there were sudden fluctuations in
wind speed and direction influenced by the topography, in which case there has been an
underestimation of the speed. Thermodynamic variables have been very poorly represented by
the small inner domain, but improved appreciably when it was expanded. The simulated
temperature has an average daily cycle less intense than observed and the underestimation
increases in warmer temperatures, probably caused by snow packets in the border areas. The
dew point temperature daily average cycle followed the observations. Some observed and
simulated patterns in circulation are briefly discussed. Finally, a simulation for a 13-day
period during which there were in situ measurements at the Deception Island are presented,
showing a good performance when compared to the observations. / O modelo Weather Research and Forecasting (WRF) foi rodado em alta resolução com
três grades aninhadas (nesting) de 12 km, 3 km e 1 km, em Shetland do Sul e
particularmente na baía da ilha Deception, durante o período de 5 a 23 de fevereiro de
2011, na Operação Antártica 29. Os dados foram medidos in situ, pelo Navio Polar
Almirante Maximiano da Marinha do Brasil, com frequência de observação de 1 hora. As
variáveis medidas e simuladas são pressão, temperatura, ponto de orvalho, temperatura da
água do mar, velocidade e direção do vento. Para a entrada no modelo foram utilizados os
dados provenientes do modelo global do National Center for Environmental Prediction
(NCEP) com 1º de resolução horizontal, atualizados a cada 6 horas. Foram testadas duas
opções de domínios na grade mais interna, uma com 127 e outra com 187 pontos em cada
direção horizontal. Também foram consideradas duas configurações para o WRF, sendo as
principais diferenças entre elas as parametrizações de microfísica de neve e difusão
térmica do solo. A variável melhor representada foi a pressão na superfície, uma vez que
esta depende quase que exclusivamente dos padrões meteorológicos de grande escala,
tendo pequena variação na microescala. A direção e velocidade do vento a 10 m da
superfície também apresentaram uma acurácia, exceto quando ocorrem flutuações bruscas
na direção e velocidade do vento influenciado pela topografia próxima, ocorrendo uma
subestimação na velocidade. As variáveis termodinâmicas apresentaram uma
representação muito deficiente com o domínio interno menor, mas melhoraram
consideravelmente quando este foi expandido. A temperatura simulada apresentou um
ciclo médio diário menos intenso que o observado e a subestimativa aumenta nos períodos
mais quentes, provavelmente pelos pacotes de neve nas áreas de fronteira. Já a
temperatura do ponto de orvalho seguiu o ciclo diário médio das observações
apresentando boas concordâncias com os dados observados. Alguns padrões observados e
simulados de circulação são discutidos brevemente. Por fim, uma simulação para um
período de 13 dias em que haviam medidas realizadas diretamente na Ilha Deception é
apresentada, apresentando um bom desempenho.
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EFEITO DE ÉPOCA DE SEMEADURA NA QUALIDADE FISIOLÓGICA E SANITÁRIA DE SEMENTES DE SOJA EM DOIS LOCAIS DE MATO GROSSO DO SUL NA SAFRA 2004/2005 / Effect of sowing date in the physiological and sanitary quality of soybean seeds in two places of Mato Grosso do Sul Brazil in 2004/2005 cropping seasonTolentino Júnior, Clóvis Ferreira 17 December 2007 (has links)
Made available in DSpace on 2016-02-26T12:59:45Z (GMT). No. of bitstreams: 1
ClovisFerreiraTolentinoJr.pdf: 826530 bytes, checksum: 77092114a46071787ede642e6bb947cd (MD5)
Previous issue date: 2007-12-17 / The selection of appropriate areas for the production of soybean seeds of high quality requires inquiry studies, especially in tropical regions. Some researchers believe that in the biggest part of the region of the Cerrados, in the Central Brazil, the climatic conditions are not favorable to the production of soybean seeds with good quality, once the quality of the seeds is highly influenced by the climatic conditions under which they had been produced. The objective of this work was to evaluate the physiological and sanitary quality of seeds of six soybean cultivars at four sowing dates in Ponta Porã and Maracaju, Mato Grosso do Sul, Brazil. The physiological quality of the seeds was evaluated by the tetrazolium test and the standard germination test and the sanitary quality by the Blotter test. The temperature and precipitation were registered during the experimental period. The seeds produced in Ponta Porã presented better physiological quality that the ones produced in Maracaju. The reduced precipitations and the high temperatures during the reproductive phase of the cultivars plants in both places had favored the low pathogen incidence in the seeds. It was not possible to establish the best sowing date for harvest of seeds with better physiological and sanitary quality / A seleção de áreas apropriadas para a produção de sementes de soja de alta qualidade requer estudos de investigação, especialmente em regiões tropicais. Alguns pesquisadores acreditam que na maior parte da região do Cerrado do Brasil Central, as condições climáticas não são favoráveis à produção de sementes de soja de boa qualidade, uma vez que a qualidade das sementes é altamente influenciada pelas condições climáticas sob as quais foram produzidas. O objetivo deste trabalho foi avaliar a qualidade fisiológica e sanitária de sementes de seis cultivares de soja produzidas em quatro épocas de semeadura em Ponta Porã e Maracaju, Mato Grosso do Sul. A qualidade fisiológica das sementes foi
avaliada pelo teste de tetrazólio e pelo teste padrão de germinação, e a qualidade sanitária pelo Blotter test. Foi realizado o monitoramento da temperatura e precipitação ao longo das épocas experimentais. As sementes produzidas em
Ponta Porã apresentaram melhor qualidade fisiológica que as produzidas em Maracaju. As reduzidas precipitações e as altas temperaturas durante a fase reprodutiva das cultivares em ambos os locais favoreceram a baixa incidência de patógenos nas sementes. Não foi possível estabelecer a melhor época de
semeadura para colheita de sementes com melhor qualidade fisiológica e sanitária
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Changes in the South Atlantic Subtropical Gyre circulation from the 20th into the 21st century / Mudanças na circulação do Giro Subtropical do Atlântico Sul do século 20 para o século 21Oliveira, Fernanda Marcello de 09 March 2017 (has links)
Through analysis of large-scale ocean gyre dynamics from simulation results of the ocean component of the Community Earth System Model version 1 - the Parallel Ocean Program version 2 (CESM1-POP2) - this study builds upon existing research suggesting recent changes in the circulation of global subtropical gyres with respect to the South Atlantic Ocean. Results all point to an increase in the total counterclockwise circulation and a southward displacement of the sub- tropical gyre system. The northern boundary of the South Atlantic Subtropical Gyre (SASG) is represented by the bifurcation of the southern branch of the South Equatorial Current (sSEC) into the North Brazil Undercurrent/Current (NBUC/NBC) to the north and the Brazil Current (BC) to the south. The sSEC Bifurcation Latitude (SBL) dictates the partition between waters flowing poleward and those flowing equatorward. Although a northward migration of the SBL would be expected with the gyre spin up and associated poleward transport increase, the SBL migrates southwards at a rate of 0.051o/yr, in conjunction to a substantial increase in the equatorward advection of waters within the sSEC-SBL-NBUC system, which is included in the upper-branch of the Atlantic Meridional Overturning Circulation. / Através de análises da dinâmica de grande-escala do giro oceânico, proveniente dos resultados de simulação da componente oceânica do Community Earth System Model versão 1 - o Parallel Ocean Program versão 2 (CESM1-POP2) - este estudo se baseia em estudos prévios sugerindo mudanças recentes na circulação dos giros subtropicais globais, com respeito ao oceano Atlântico Sul. Os resultados apontam para uma intensificação da circulação anti-horária e um deslocamento para sul de todo o sistema do giro subtropical. A borda norte do Giro Subtropical do Atlântico Sul (GSAS) é representada pela bifurcação do ramo sul da Corrente Sul Equatorial (CSEs) em Subcorrente/Corrente Norte do Brasil (SCNB/CNB) para norte e Corrente do Brasil (CB) para sul. A Latitude da Bifurcação da CSEs (LBC) determina a partição entre as águas fluindo em direção ao pólo e aquelas fluindo em direção ao equador. Embora seja esperada uma migração para norte da LBC com a aceleração da circulação do giro e consequente aumento do transporte em direção ao pólo, a LBC migra para sul a uma taxa de 0.051o/ano. Esta migração ocorre em conjunto à um aumento substancial na advecção de águas em direção ao equador com o sistema CSEs-LBC-SCNB, o qual está incluso no ramo superior da Circulação de Revolvimento Meridional do Atlântico.
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