• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 45
  • 41
  • 26
  • 10
  • 8
  • 7
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 155
  • 155
  • 42
  • 36
  • 31
  • 30
  • 30
  • 30
  • 30
  • 28
  • 25
  • 23
  • 21
  • 20
  • 20
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

“Caracterización de la dieta de Spheniscus humboldti ¨Pingüino de Humboldt¨ durante los años 1992, 1993 y 1996 procedentes de los alrededores de Punta San Juan- Ica, Perú”

Luna Donoso, Andrea Julia January 2016 (has links)
El objetivo del presente trabajo fue caracterizar la dieta de Spheniscus humboldti de los alrededores de Punta San Juan, Punta Caballa y Sombrerillo-Ica, Perú durante los años 1992, 1993 y 1996. Se estudiaron 378 estómagos provenientes de captura incidental durante operaciones de pesca artesanal de Seriorella violacea, utilizando redes agalleras. La alimentación de S. humboldti comprendió 27 especies. De acuerdo al coeficiente alimentario numérico, los ítems primarios fueron: Teuthida, Isacia conceptionis, Cheilodactylus variegatus, Sciaena deliciosa, Seriolella violacea, Stromateus stellatus, Eugraulis ringens, Opistonema liberate, Normanichthys crockery, Odonthestes regia, Myctophum nitidulum, Merluccius gayi y Leuroglossus stilbius. La dieta de S. humboldti se considera especialista y con amplitud de dieta. Se observaron diferencias en la dieta de S. humboldti interanual, debido a que en 1992 los ítem presa primarios fueron: Teuthida, C. variegatus, E. ringens, O. liberate, N. crockery, O. regia, M. nitidulum y M. gayi. En el año 1993 los ítem presa primario fueron: Teuthida, I. conceptionis, C. variegatus, S. stellatus, E. ringens, N. crockery, O. regia, M. gayi y L. stilbius. En el año 1996 los ítems primarios fueron: Teuthida, E. ringens, N. crockery y O. regia. Se observaron ligeras diferencias en la dieta de S. humboldti interestacional. Los valores de Shannon-Wiener dan un rango entre 0,07 a 0,47, y el índice de amplitud de nicho de Levin fue de 0,04 a 0,13, por lo tanto, se trata de un depredador especialista. El traslapamiento de la dieta mediante el índice de Bray-Curtis indica que a nivel interestacional por años la diferencia fue de 0,20 Existieron diferencias en la dieta de S. humboldti en relación a los eventos oceanográficos, observándose una diferencia entre 1992 (evento de El Niño), 1996 (evento influenciado por La Niña) y 1993 (año influenciado por El Niño).This work aimed at characterizing the diet of the Spheniscus humboldti from around Punta San Juan, Punta Caballa and Sombrerillo (Ica, Peru) in 1992, 1993 and 1996. Three hundred seventy-eight stomachs from the incidental catch of Seriorella violacea in subsistence fishing operations using gillnets. The diet of the S. humboldti comprised 27 species. Per the numerical food coefficient, the primary items were the following: Teuthida, Isacia conceptionis, Cheilodactylus variegatus, Sciaena deliciosa, Seriolella violacea, Stromateus stellatus, Eugraulis ringens, Opistonema liberate, Normanichthys crockery, Odonthestes regia, Myctophum nitidulum, Merluccius gayi and Leuroglossus stilbius. The S. humboldti is considered a specialist species with dietary breadth. Differences were noted in the diet of the S. humboldti interanual, since, in 1992, the primary prey items were the following: Teuthida, C. variegatus, E. ringens, O. liberate, N. crockery, O. regia, M. nitidulum and M. gayi. In 1993, the primary prey items were Teuthida, I. conceptionis, C. variegatus, S. stellatus, E. ringens, N. crockery, O. regia, M. gayi and L. stilbius. In 1996, the primary prey items were Teuthida, E. ringens, N. crockery and O. regia. Slight differences were noted in the interseasonal diet of the S. humboldti. The Shannon-Wiener index values result in a range between 0,07 and 0,47, and Levin’s niche breadth ratio resulted in 0,04 to 0,13. Therefore, it is a specialized predator. The overlap in the diet, determined through the Bray-Curtis ratio, indicates that, seasonally and by year, the difference was 0,20. There were differences in the diet of the S. humboldti regarding oceanographic events. A difference was observed between 1992 (El Niño event), 1996 (event influenced by La Niña) and 1993 (a year influenced by El Niño).
22

Dinâmica populacional do caranguejo baú Hepatus pudibundus (Herbst, 1785) (Decapoda Aethroidea) numa área de pesca intensa: comparação num intervalo de 20 anos /

Teles, Jeniffer Natália January 2019 (has links)
Orientador: Giovana Bertini / Resumo: O objetivo deste estudo foi analisar e comparar a distribuição espaço-temporal de Hepatus pudibundus num intervalo de 20 anos, associado com os fatores ambientais, na Enseada de Ubatuba, SP. As coletas foram realizadas em dois períodos, de setembro/1995 a agosto/1996 (1º período = 1ºP) e setembro/2016 a agosto/2017 (2º período = 2ºP), em 5 áreas amostrais (5m, 10m e 15m, área exposta e área abrigada), com um barco de pesca camaroeiro. Os fatores ambientais coletados foram: temperatura e salinidade de fundo e superfície, sedimento para análise de phi e teor de matéria orgânica. Após 20 anos do primeiro período de estudo na Enseada de Ubatuba foi possível detectar que houve um aumento na deposição de sedimentos finos em todas as áreas amostradas. Em relação à população de H. pudibundus observou-se que no 1ºP foram coletados 865 caranguejos e no 2ºP 4222. Essa maior abundância de indivíduos no 2ºP pode ser devido a coleta ter sucedido um evento intenso de El Niño, que faz que com a ACAS (Águas Centrais do Atlântico Sul) permaneça mais tempo na região externa da enseada, diminuindo a temperatura da água, e podendo fazer com que os indivíduos se abriguem dentro da enseada. Houve uma alteração da distribuição espacial dos indivíduos, principalmente, dos caranguejos adultos, os quais mudaram da área exposta e 15m no 1ºP para área abrigada no 2ºP. Tal mudança pode estar relacionada ao aumento de sedimentos finos nesta área e por ela ser uma região de exclusão natural de pesca, o que ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objective of this study was to analyze and compare the spatio-temporal distribution of Hepatus pudibundus in a 20-year interval, associated with environmental factors, in the Ubatuba Bay, SP. The samples were collected in two sampling periods, from September/1995 to August/1996 (1st period = 1P) and September/2016 to August/2017 (2nd period = 2P), in five areas (5m, 10m, 15m, exposed area and sheltered area) with a shrimp fishing boat. The environmental factors collected were bottom and surface temperature and salinity, sediment for phi analysis and organic matter content. After 20 years of the first study period in the Ubatuba Bay, it was possible to detect that there was an increase in the deposition of fine sediments in all the areas sampled. In relation to the population of H. pudibundus it was observed that in the 1P were collected 865 crabs and in the 2ºP 4222. This greater abundance of individuals in the 2P can be due to the collection to have happened an intense event of El Niño, that causes that with ACAS (Central Waters of the South Atlantic) remain longer in the outer region of the bay, lowering the water temperature, and may cause individuals to shelter within the bay. There was a change in the spatial distribution of the individuals, mainly of the adult crabs, who changed from the exposed area and 15m in the 1P to the sheltered area in the 2P. Such change may be related to the increase of fine sediments in this area and because it is a region of natural exclu... (Complete abstract click electronic access below) / Mestre
23

Condições térmicas ambientais relacionadas à exploração florestal na Amazônia Central

Nascimento, Kauê Augusto Oliveira 21 February 2017 (has links)
Submitted by Inácio de Oliveira Lima Neto (inacio.neto@inpa.gov.br) on 2017-05-29T14:22:31Z No. of bitstreams: 2 MSC_KAUENASCIMENTO_CFT.pdf: 3264146 bytes, checksum: 9a7127729916fc0775c3deec91756e4a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-05-29T14:22:31Z (GMT). No. of bitstreams: 2 MSC_KAUENASCIMENTO_CFT.pdf: 3264146 bytes, checksum: 9a7127729916fc0775c3deec91756e4a (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-02-21 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The Amazon covers an extensive area with forests that are poorly managed. There are challenges to forest management, poor human resources training, lack of advanced technology and poor working conditions. This causes poor quality of logging, generating unsustainability. This activity requires large contingent and high physical load of workers. The thermal comfort at work in tropical regions is between 20 and 24 °C, in the Central Amazon the day averages exceed 28 °C. To worsen the situation, El Niño phenomena cause an increase in average temperatures in the region. The current thermal conditions and forecasts for the region are under the requirements of a controversial labor norm (NR-15). The need for well-being at work, to improve the quality, health and safety in the forest logging, justify the study. The objective of this research was to investigate the relationship between environmental thermal conditions and natural pauses and the performance of workers in forest logging. The data were collected by operation: cutting, pre-extraction, extraction and patio. The observed data were compared with the national standard (NR-15 Annex 03) and consulted NHO-06 and NIOSH standards. The WBGT variables and natural pauses (%/hour) were collected, comparing the pause patterns of the standard with that observed in the field. Data were collected on heart rate, personal variables (age, weight and height) and estimated the physical work load by two different methods: Annex C ISO 8996 and Apud (1989). Performance variables (operational cycle, productivity, mechanical interruption, hour and natural pauses) and safety (perception of heat and psychophysiological effects) were collected. These variables were analyzed using MANOVA and multiple regressions. Environmental variables of the El Niño phenomenon (November 2015), with the local climate and data of a time without phenomenon (November 2010), were collected and compared by means of t tests. Based on WBGT, at 8 a.m., it is necessary to apply pauses, according to NR-15. The pauses were intermittent, larger every 02 hours of work. The natural pauses represented about 30% of the pauses of the norm, and their behavior was not altered by the variation of WBGT. The method of Apud (1989) found physical load and pauses consistent with the norm. The ISO 8996 method found a very variable physical load, for the same occupation, related to personal variables. The variables productivity and natural pauses were strongly influenced by the mechanical interruption, with probable influence of the hour. All workers showed discomfort with the heat. The statistical differences between the environmental variables of the El Niño Godzilla with the climate and the 2010 study were virtually certain. The air temperature was higher and the relative humidity was lower. The adequacy of the working conditions in the heat exposure, would result in workers' welfare, with consequent improvements in health, safety, quality and performance of forest logging, essential requirements for the sustainability of forest management in the Amazon under the current and future scenario of climate change. / A Amazônia abrange uma área extensa com florestas ainda pouco manejadas. Há desafios para o manejo florestal, pela má formação de recursos humanos, falta de tecnologia avançada e condições de trabalho precárias. Isto causa a baixa qualidade da exploração florestal, gerando a insustentabilidade. Esta atividade exige grande contingente e alta carga física dos trabalhadores. O conforto térmico no trabalho em regiões tropicais está entre 20 e 24°C, na Amazônia Central as médias diurnas superam os 28°C. Para agravar a situação, fenômenos El Niño, causam aumento das temperaturas médias na região. As condições térmicas atuais e de previsões para a região, estão sob as exigências de uma norma trabalhista controversa (NR-15). A necessidade de bem estar laboral, para melhoria da qualidade, saúde e segurança na exploração florestal, justificam o estudo. Este trabalho teve como objetivo, investigar as relações das condições térmicas ambientais com o regime de pausas naturais e com o desempenho dos trabalhadores na exploração florestal. Os dados foram coletados por operação: corte, pré-arraste, arraste e pátio. Os dados observados foram confrontados com o estipulado pela norma nacional (NR-15 anexo 03) e consultadas NHO-06 e NIOSH. Foram coletadas as variáveis IBUTG e pausas naturais (%/hora), com isso, foi comparado o regimes de pausas da norma com o observado em campo. Foram coletados dados de frequência cardíaca, variáveis pessoais (idade, peso e altura) e estimada a carga física de trabalho por meio de dois métodos diferentes: anexo C ISO 8996 e Apud (1989). Foram coletadas as variáveis de desempenho (ciclo operacional, produtividade, interrupção mecânica, hora do dia e pausas naturais) e segurança (percepção de calor e efeitos psicofisiológicos). Estas variáveis foram analisadas por meio de MANOVA e regressões múltiplas. Foram coletadas e comparadas variáveis ambientais do fenômeno El Niño (Novembro 2015), com o clima local e com dados de uma época sem fenômeno (Novembro 2010), por meio de testes t. Com base em IBUTG, a partir de 08 horas é necessária aplicação de pausas, segundo a NR-15. As pausas foram intermitentes, maiores a cada 02 horas de trabalho. As pausas naturais representaram cerca de 30% das pausas da norma, e seu comportamento não foi alterado pela variação de IBUTG. O método de Apud (1989) encontrou carga física e pausas condizentes com a norma. O método da ISO 8996 encontrou carga física muito variável, para a mesma ocupação, relacionados às variáveis pessoais. As variáveis produtividade e pausas naturais foram muito influenciadas pela interrupção mecânica, com provável influência da hora do dia. Todos os trabalhadores demonstraram desconforto com o calor. Foram praticamente certas as diferenças estatísticas entre as variáveis ambientais do El Niño Godzilla com o clima e com o estudo de 2010. A temperatura do ar foi superior e a umidade relativa do ar foi inferior. As adequações das condições de trabalho na exposição ao calor, acarretariam no bem estar dos trabalhadores, com consequentes melhorias na saúde, na segurança, na qualidade e no desempenho da exploração florestal, requisitos essenciais para a sustentabilidade do manejo florestal na Amazônia, sob o cenário atual e futuro da mudança climática.
24

Variabilidade de tsm no Atlântico Tropical em respostas às teleconexões de diferentes Enos e seus impactos na precipitação na América do Sul.

FIGLIUOLO, Guilherme Cordeiro 29 June 2017 (has links)
Submitted by Inácio de Oliveira Lima Neto (inacio.neto@inpa.gov.br) on 2017-09-04T14:37:18Z No. of bitstreams: 1 DISSGCF_vf.pdf: 8952149 bytes, checksum: 24fc925d7eeb0858019bdcb1786f333f (MD5) / Made available in DSpace on 2017-09-04T14:37:18Z (GMT). No. of bitstreams: 1 DISSGCF_vf.pdf: 8952149 bytes, checksum: 24fc925d7eeb0858019bdcb1786f333f (MD5) Previous issue date: 2017-06-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Changes in teleconnection patterns in response to different types of El Niño Southern Oscillation (ENSO), classified by the positioning of SST anomalies in: East Pacific (EP) and Central Pacific (CP) and their impacts on SST variability on the Tropical North Atlantic (TNA) and tropical South American precipitation, during the positive and negative phases of Atlantic Multidecadal Oscillation (AMO) were evaluated for the 1901-2010 period, using the composite method for the quarterly anomalies. These analyses were applied to atmospheric and oceanic anomaly variable fields (Sea Surface Temperature-SST, precipitation, 200 hPa stream function, 1000 hPa horizontal winds and mean sea level pressure). Regarding the distribution of ENSO events, the results shows consistency with previous studies on the relation between AMO and ENSO, with the ENSO events occurring more frequently during the negative phase of AMO. The El Niño (La Niña) events, independent of the type (EP or CP), during the positive (negative) phase of AMO were followed by a warming (cooling) on TNA after their mature phases. The dynamics of this relationship involve variations in Walker's circulation or variations in the Pacific North American (PNA) teleconnection pattern. On the other hand, for the El Niño (La Niña) years that occurred during the negative (positive) phase of the AMO, no significant variations were observed in the SST over the TNA. These results shows the important role of the SST anomaly precondition in the Tropical Atlantic and north, associated to AMO phases, in defining teleconnection patterns in response to ENSO. When ENSO and AMO are both in the same phase, the patterns of extratropical teleconnections are dominant, through the PNA, in addition, they have anomalies with the same sign in the tropical Pacific and in the TNA. On different phases of ENSO and AMO, the tropical teleconnection patterns are dominants, through the Walker circulation and the inter-basin zonal gradient that is intensified due to the observed SST anomalies in the Pacific Ocean and the neutral pattern in the Atlantic. These circulations pattern changes affect the rainfall over tropical South America. The results presented here highlight the importance of low frequency oscillations in defining the teleconnection patterns between the Pacific and AT oceans, not discussed previously. / As mudanças nos padrões de teleconexões em resposta aos diferentes tipos do evento El Niño-Oscilação Sul (ENOS), classificado pelo posicionamento das anomalias de TSM em: evento do Pacífico Leste (EP) e Pacífico central (CP) e seus impactos na variabilidade da TSM sobre o Atlântico Tropical Norte (ATN) e na precipitação da América do Sul tropical (AST), durante as fases positiva e negativa da Oscilação Multidecenal do Atlântico (AMO) foram avaliadas durante o período 1901-2010, utilizando o método de composições para as anomalias trimestrais. Essas análises foram aplicadas aos campos de anomalias de variáveis atmosféricas e oceânicas (Temperatura da Superfície do Mar-TSM, precipitação, função de corrente em 200 hPa, ventos horizontais em 1000 hPa e Pressão ao nível médio do mar). Em relação à distribuição de eventos ENOS, os resultados são consistentes com os de estudos anteriores que evidenciam a relação entre a AMO e o ENOS, com maior frequência de eventos ENOS durante a fase fria da AMO. Os eventos El Niño (La Niña), independentemente do tipo (EP ou CP), durante a fase positiva (negativa) da AMO foram acompanhados por um aquecimento (resfriamento) no ATN após suas fases maduras. A dinâmica dessa relação envolve variações na circulação de Walker ou variações no padrão de teleconexão Pacífico/América do Norte (PNA). Por outro lado, para os anos de El Niño (La Niña) que ocorreram durante a fase negativa (positiva) da AMO não foram notadas variações significativas na TSM sobre o ATN. Esses resultados mostram o importante papel da pré-condição de ATSM no AT e norte, associadas às fases da AMO, na definição dos padrões de teleconexões em resposta ao ENOS. Quando os eventos de ENOS encontram-se na mesma fase que a AMO, os padrões de teleconexões extratropicais são dominantes, através do PNA, além disso, apresentam anomalias de mesmo sinal no Pacífico tropical e ATN, com uma pequena defasagem. Em fases distintas do ENOS e AMO, os padrões de teleconexões tropicais são predominantes, através da célula de Walker e do gradiente zonal inter-bacias, que é intensificado devido as anomalias de TSM observadas sobre o oceano Pacífico e o padrão neutro no Atlântico. Essas mudanças nos padrões de circulação afetam os padrões de precipitação na AST. Os resultados aqui apresentados destacam a importância das oscilações de baixa frequência na definição dos padrões de teleconexões entre os oceanos Pacífico e AT, não discutidos anteriormente.
25

Patrones de variabilidad y las pesquerías en el Pacífico Sud Este

Espino Sánchez, Marco Antonio January 2014 (has links)
En el Pacífico Oriental, se dan patrones de variabilidad interanuales, decenales y seculares asociados a factores de variabilidad como el ENSO, PDO y PSV, estableciendo condiciones transitorias y relativamente permanentes, determinadas por la dinámica del Ecosistema de Afloramiento Peruano, que ocupa gran parte del Pacífico Sud Este. El Niño es un evento trascendental en la dinámica oceánica pero transitorio y, luego de algunos meses a no más de 2 años concluye, retornando el sistema a las condiciones propias del momento decenal (periodicidad) imperante, cálido, frío o templado según se ha diferenciado por análisis de distancia euclidiana. La periodicidad está afectada por la secularidad definida por la varianza del Índice de Oscilación del Sur. Tanto la periodicidad como la secularidad constituyen estados climáticos que afectan las economías de los países ribereños con pesquerías importantes a nivel regional y mundial. En la década de los 70s, la periodicidad decenal motivó una alternancia entre la anchoveta (Engraulis ringens) y la sardina (Sardinops sagax sagax) determinando que la productividad del ecosistema pase de biomasas de anchoveta de entre 10 a 15 millones de toneladas, a biomasas de sardina de 5 y 10 millones; y, en los 90s un retorno de dominancia de la anchoveta. Esto motiva cambios en la matriz productiva, tanto en la extracción, el procesamiento, como el mercado debido a que se trata de especies totalmente diferentes. Asimismo, otras especies como el jurel (Trachurus murphyi), caballa (Scomber japonicus), bonito (Sarda chiliensis) y calamar gigante (Dosidicus gigas), son también afectadas por los cambios decenales que a su vez son exacerbados o atenuados por la secularidad; sin embargo, la variabilidad ha sido una marca de este ecosistema desde sus orígenes y, las especies están adaptadas a estos cambios, lo que aún no se adapta y requiere de mecanismos aún sofisticados de ajuste son los sistemas productivos regulados por el ser humano. Basadas en la periodicidad y la secularidad se modela retrospectiva y prospectivamente la abundancia de los recursos pesqueros pelágicos en el periodo comprendido entre 1500 y 2050 para el Pacífico Sudoriental. / Tesis
26

Simulation of tropical pacific circulation anomalies with linear atmosphere and ocean models

Dixit, Sanjay 12 August 1987 (has links)
A simple atmosphere and ocean model of relevance to El Nino and Southern Oscillation (ENSO) is discussed. Both the atmosphere and ocean models are two layer, three dimensional, linear and baroclinic, and generally follow the Oregon State University coupled general circulation model. However, the parameterization differs considerably from previous work in the treatment of the atmospheric latent heat release. This new parameterization follows the formula used in the theory of conditional instability of the second kind (CISK). In this the latent heat release is proportional to the low level convergence. Utilizing the "Comprehensive Ocean Atmosphere Data Set" (COADS), which contains all oceanic and atmospheric surface variables over the global ocean from 1946-1979, experimental model results are discussed for determination of the validity of the parameterizations. In particular, the years 1957, 1965 and 1972 in which El Nino events occurred are examined. The parameterization is deemed to be realistic, and should permit simulation of the El Nino upon coupling the two models. / Graduation date: 1988
27

A study of El Niño/southern oscillation : numerical experiments and data analysis

Ahn, Joong Bae 23 August 1990 (has links)
For the purpose of investigating the fundamental nature of the interannual oscillation observed in the tropical Pacific in conjunction with El Nino/Southern Oscillation (ENSO), the Comprehensive Ocean Atmosphere Data Set was analyzed. Based upon this analysis, an "intermediate" tropical atmosphere-ocean coupled model was developed. For reason of their particular importance to atmosphere-ocean interactions, moisture processes such as condensation-convergence, evaporation-sea surface temperature and evaporation-wind feedbacks were given special emphasis in both the data analysis and modeling processes. The atmospheric component of the model is based on the first baroclinic mode, which is driven by the atmospheric internal heating. The oceanic model consists of two layers with an imbedded oceanic mixed-layer, by which SST is predicted. The present study has demonstrated that despite the structural simplicity of the oceanic model, it is capable of simulating mean oceanic circulation. In preparation for coupling, individual models were first tested with the use of appropriate time-dependent boundary conditions specified from the composite ENSO data. Both model simulations reproduced the major features associated with the ENSO events. Coupling was performed following the imposition of wind stress anomalies over the western Pacific for a given time period and the removal of all external forcing for a period of eight years thereafter. The coupled responses simulated during the the first two-year period provided reasonable simulations of the following ENSO-like features: the appearance of warm sea-surface temperature anomalies in the central Pacific, deepening/shallowing of mixed-layers in the eastern/western Pacific, weakening of the trades in the central Pacific, strengthening/weakening of the North Equatorial Counter Current/South Equatorial Currents, and enhanced convective activities around the dateline. The long-term coupled integration showed a pattern of interannual oscillation over a period of approximately three years. The results obtained from this coupling study have illustrated (1) that the necessary condition for the interannual oscillation is the interaction between the atmosphere and the ocean and (2) that it is likely that oceanic wave dynamics plays a crucial role in the determination of the growth and decay of ENSO events. / Graduation date: 1991
28

Does El Nino affect the capture fishery production in the Pacific Ocean?

Liu, Ting-An 16 January 2012 (has links)
This study examines the non-linear cointegrated relationship between capture production and the El Nino/La Nina index using the quantile technique proposed by Xiao (2009). According to the annual sample data of 6 Major Fishing Areas in the Pacific Ocean from 1950 to 2008, our empirical findings provide strong evidence that the cointegrating coefficients follow a time-varying process. They also imply that most of these long-run relationships are influenced by potential shocks over time rather than from maintaining a constant effect consistently. Overall, the contributions of this study not only stresses the importance of the quantile property in cointegrated models, but also provides a viewpoint on the long-run approach that the overall El Nino and La Nina act as engines for capture production.
29

Analysis of Upwelling Changes in the Eastern Equatorial Pacific during El Niño Southern Oscillation

Perugachi Salamea, Carlos 2011 December 1900 (has links)
The ocean reanalysis Simple Ocean Data Assimilation (SODA) 2.2.4 is used to explore the changes in upwelling from normal conditions to either El Nino or La Nina conditions. Physical and thermodynamic variables from the reanalysis are used to explore the structure and behavior of El Nino Southern Oscillation (ENSO) events. The results of this analysis show that sea surface temperature (SST), entrainment velocity, wind stress, mixed layer depth, wind curl, and heat content anomalies are in general agreement with ENSO theory. Interestingly, the distribution of upwelling based on the entrainment velocity is very patchy, which led us to explore zonal and meridional sections of vertical velocity. We used three methods to compute changes in upwelling during ENSO events. The first method computes upwelling within the areas of SST anomalies during ENSO events. During El Nino events upwelling shows prominent decadal variability, while during La Nina the decadal variability is weaker. A new upwelling index is used for the second method, and upwelling is computed in the areas of strong upwelling anomalies. The variability of upwelling is higher in periods of reduced upwelling than in periods of strong upwelling. Despite the fact that the new index is computed independently, it agrees in the timing of the index used to define ENSO events for this research. The first and second methods show that the amplitude of SST anomalies and upwelling anomalies do not have a direct relationship, suggesting that upwelling does not explain all of the variance in SST. The last method used is to compute changes in upwelling in the Nino 1+2 region during ENSO events. In the east Pacific there is almost no correlation between upwelling and SST anomalies during ENSO, but this might be attributed to the fact that the Nino 1+2 region is a relatively small region compared to the Nino 3.4 region that is used to define ENSO events. In general, the time series of SST and upwelling anomalies agree well just in the cases when ENSO events are prominently in the eastern Pacific. A comparison between yearly fisheries data from Ecuador and Peru and monthly data of SST anomalies during ENSO years is presented showing that during El Nino events the fish catch decreases and during La Nina events the fish catch increases. We infer that the increase or decrease in fish catch is associated to changes in fish populations, and that these changes are mainly due to availability of nutrients and changes in temperature during ENSO events.
30

Carbon Dioxide Variation in the Taiwan Strait and the Northern South China Sea

Huang, Ting-Hsuan 10 September 2009 (has links)
The dynamics of marginal seas is complex in terms of carbon dioxide absorption and release. This thesis analyzes data collected in the southern Taiwan Strait and in the South China Sea. In order to deduct the influence of temperature on the fCO2, fCO2 is normalized to the average water temperature (fCO2 mean). In the spring of 2008, in the Taiwan Strait, when salinity was smaller than approximately 33.8, measured fCO2 mean and salinity had a negative correlation; but when the salinity was higher than approximately 33.8, the correlation was positive. When salinity was smaller than apprx. 33.8, fCO2 cal. mean correlated slightly negatively to chlorophyll. This indicates that the low fCO2 cal. was not only caused by the increase of the CO2 solubility at lower temperatures, but also by the biotic photosynthesis. On the contrary, when the salinity was higher than apprx. 33.8, fCO2 cal. mean and the chlorophyll held positive correlation. It indicates that the influence of photosynthesis was reduced. In this case, the primary factor of fCO2 cal. change was due to the mixing of the high normalized dissolved inorganic carbon (NDIC=35¡ÑDIC/S) China Coastal Current with low NDIC seawater. With a raise of seawater temperature, then a decrease of the CO2 solubility, seawater became a source of carbon dioxide. In the summer of 2008, the northern South China Sea was influenced by Pearl River plume, resulting in lower fCO2 and salinity. The fCO2 of the China coast was influenced not only by the Pearl River plume, but also by the Jiulong River plume and upwelling. The Taiwan Strait water mass mainly contains the South China Sea water, a Kuroshio branch and the China Coast Current. During an El Niño year, the monsoon weakens, so that the volume of Kuroshio entering the South China Sea increases. However, for La Niña years, the monsoon strengthens, therefore the volume of the Kuroshio entering the South China Sea decreases. As a result, the Taiwan Strait water changes interannually due to different mixture of seawater of the Kuroshio and the South China Sea. The southern Taiwan Strait could be divided into the Penghu Channel and the western strait. During an El Niño summer, the Penghu Channel is occupied by waters with high temperature, salinity and pH, but low NDIC and nutrients. This is because more Kuroshio waters enter the South China Sea, then move northward to the southern Taiwan Strait. The hydrology in the Penghu Channel in normal years shows different result from season to season. In the summer, the Penghu Channel contains low temperature, salinity and pH water. In winter, waters with high salinity and pH, but low AOU, NDIC and nutrients prevail. This indicates that less Kuroshio waters enter the South China Sea in summer than in winter. The hydrology of the Penghu Channel changes decidedly from season to season in a normal year but spring, summer and fall have no clear change in the El Niño period, because more Kuroshio waters enter the South China Sea in summer. The wind effect during the El Niño period becomes weakened, have the hydrology during summer monsoon is similar to the hydrology in spring and summer. The waters of the Penghu Channel reach the highest pH, but the lowest AOU, NDIC and nutrients in winter. Older waters from upwelling move to the north in the western Strait during spring and fall in a normal year. However, during the El Niño period, possibly due to the weaker monsoon, such upwelling signal is reduced. Waters of the western strait in winter have higher temperature, salinity and pH, but lower NDIC during the El Niño period compared to a normal year. This indicates that the El Niño influences not only the Penghu Channel but also the entire southern Taiwan Strait in winter.

Page generated in 0.0591 seconds