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Doctoral Thesis
DOI
10.11606/T.21.2008.tde-24062008-155722
Document
Author
Full name
Rosio Del Pilar Camayo Maita
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2008
Supervisor
Committee
Campos, Edmo Jose Dias (President)
Camargo, Ricardo de
Castro Filho, Belmiro Mendes de
Harari, Joseph
Lorenzzetti, Joao Antonio
Title in Portuguese
O papel de efeitos locais e remotos em variabilidades do sistema de ressurgência ao largo da costa oeste da América do Sul durante o El Niño
Keywords in Portuguese
Efeitos do El Ni~no na Ressurg^encia Costeira do Peru
Modelo de Brink
Ondas Aprisionadas na Costa
Ondeletas.
Abstract in Portuguese
Ao largo da costa oeste da Am´erica do Sul o sistema de ressurg^encia costeira apresenta uma excepcional produtividade, um resultado da alta efici^encia do ecossistema biol´ogico em converter a produ¸c~ao prim´aria em biomassa. Esses processos qu´?micobiol ´ogicos s~ao fortemente modulados pelo ambiente f´?sico da regi~ao. Por exemplo, durante eventos do El-Ni~no a produtividade pesqueira ´e fortemente prejudicada em resposta a uma inibi¸c~ao da ressurg^encia costeira. Apesar disso ser um fato j´a bastante conhecido desde ´epocas pr´e-colombianas, muita d´uvida ainda persiste sobre o mecanismo pelo qual o sistema costeiro ´e afetado por esses fen^omenos de grande escala. O presente trabalho foi realizado com o objetivo de se contribuir com esse conhecimento, estudando como ocorreram as mudan¸cas do sistema durante recentes eventos El Ni~no, principalmente na escala intrasazonal. Nessa investiga¸c~ao foram utilizadas diferentes metodologias de an´alise de dados para identificar a natureza dos for¸cantes de oscila¸c~oes significativas observadas durante o El Ni~no 1997-1998. Tamb´em foi investigado se essas oscila¸c~oes foram for¸cadas remotamente e se propagaram como ondas aprisionadas na costa; quais foram suas propriedades espaciais e sua propaga¸c~ao longo da costa. A primeira parte do trabalho consiste na an´alise da variabilidade temporal e a caracteriza¸c~ao das flutua¸c~oes de baixa freq¨u^encia ocorridas durante eventos El Ni~no. Essa an´alise faz uso do espectro de ondeleta aplicado a s´eries temporais longas de dados do n´?vel do mar de esta¸c~oes costeiras distribu´?das ao longo da costa sul do Equador, costa do Peru e costa norte do Chile. O espectro de ondeleta cruzada e o espectro da coer^encia foram usados para avaliar a import^ancia relativa das for¸cantes remota e local das varia¸c~oes do n´?vel do mar associadas com os efeitos do El Ni~no 1997-1998. Na segunda parte, as flutua¸c~oes for¸cadas remotamente foram comparadas com modelos lineares simples e o modelo de Brink e Chapman (1987) para se obter as propriedades das ondas aprisionadas na costa durante o El Ni~no Extraordin ´ario (1997-1998). Uma importante conclus~ao dessas an´alises foi a constata¸c~ao de que variabilidades intrasazonais ao largo da costa do Peru durante esse El Ni~no foi, em parte significativa, o resultado da atua¸c~ao de for¸cantes remotas e locais, associadas com ondas equatoriais incidindo na Costa Oeste da Am´erica do Sul e com o efeito do vento, respectivamente.
Title in English
The role of the local and remote effects on the upwelling system variabilities along the western coast of South America, during El Niño
Keywords in English
Brink\'s Model
Coastal Trapped Waves
Effects of El Ni~no in the Peruvian Coastal Upwelling
Wavelets.
Abstract in English
Off the western coast of South America, the coastal upwelling system presents an exceptional productivity, a result of the high efficiency of the biological ecosystem in converting the primary production into biomass. These chemical and biological processes are strongly modulated by the physical environment. For instance, during El Ni~no events the fishery productivity is strongly impaired in response to an inhibition of the coastal upwelling. In spite of this fact be widely known since pre-Colombian times, much doubts still persist about the mechanism by means of which the coastal system is affected by the large scale phenomena. The present work was idealized with the intention of contributing for this knowledge, studying how occurred the changes in the system during recent El Ni~no events, with emphasis on the intraseasonal scale. In this investigation, different methodologies of data analysis were used to identify the nature of the forcing which produced significant oscillations observed during the El Ni~no 1997-1998. Also, it was investigated if these oscillations were remotely forced and propagated along the coast as coastal trapped waves; what were their spatial and propagation properties. The first part of the work consists of an analysis of the temporal variability and the characterization of the low-frequency fluctuations occurred during the El Ni~no events. This analysis uses the wavelet spectrum applied to time series of sea level data collected off southern Equador, Peru and northern Chile. The cross wavelet spectrum and coherence spectrum were used to evaluate the relative importance of local and remote forcing of the sea level, associated with effects of the 1997-1998 El Ni~no. In the second part, the fluctuations remotely forced wer compared with results of simple linear models and with the model of Brink and Chapman (1987), in order to obtain the coastal trapped waves properties during that extraordinary El Ni~no event. One important conclusion of these analyses was the confirmation that the intraseasonal variability observed offo Peru during the 1997-1998 El Ni~no was, in part, the result of remote and local forcing, associated with equatorial waves and the wind effect, respectively.
 
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Publishing Date
2008-06-25
 
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