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Doctoral Thesis
DOI
https://doi.org/10.11606/T.14.2022.tde-25102022-213227
Document
Author
Full name
Hugo Alves Braga
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2022
Supervisor
Committee
Ambrizzi, Tercio (President)
Freitas, Ana Carolina Vasques
Oliveira, Cristiano Prestrelo de
Raupp, Carlos Frederico Mendonça
Rueda, Victor Orlando Magana
Title in Portuguese
Propagação de Ondas de Rossby Atmosféricas e a Zona de Convergência do Atlântico Sul
Keywords in Portuguese
ENOS
Ondas de Rossby
ZCAS
Abstract in Portuguese
A relação entre a Zona de Convergência do Atlântico Sul (ZCAS) e as propagações de ondas de Rossby foram analisadas durante 34 verões austrais, de acordo com as fases positivas, negativas e neutras do El Niño Oscilação Sul (ENOS). Anomalias das componentes zonais e meridionais do vento, foram calculadas com base na climatologia de 1979-2013 no nível de 200 hPa, e submetidos ao filtro de Lanczos nas bandas temporais de 20-90 dias e 200 dias passa baixa, com a intenção de destacar as variabilidades intrassazonal e interanual, através da análise observacional das composições médias de ZCAS climatológicas e das fases positiva, negativa e neutra do ENOS. As análises desta tese foram divididas em duas partes principais, primeiramente em relação ao domínio da América do Sul, para entender o impacto da ZCAS local, e no domínio do Oceano Pacifico e Atlântico Sul, para compreender os efeitos remotos associados a ZCAS. Da América do Sul com relação as fases do ENOS são destacados; a supressão da ZCIT durante anos de El Niño e a intensificação da mesma durante eventos de La Niña; e sob o Atlântico Equatorial o cavado do nordeste aparenta ser enfraquecido durante anos de La Niña e intensificado durante os anos de El Niño, o que contribui para o estabelecimento dos Vórtices Ciclônicos de Altos Níveis (VCAN). Do Pacifico à América do Sul foram revelados diferentes guias de ondas de Rossby que interagem com a ZCAS a depender da variabilidade interanual, durante anos de El Niño as ondas são mais longas e partem do Oceano Pacifico Leste, próximo da região da Zona de Convergência do Pacifico Sul. Durante as La Niñas um trem de ondas de Rossby interhemisférico foi identificado partindo do Sudeste da Ásia e dispersando energia para a ZCAS com até 15 dias, este padrão de ondas de Rossby foi confirmado a partir de simulações numéricas com a utilização do modelo baroclínico DREAM. Posteriormente foi simulado a resposta da atmosfera a pertubações na região da ZCAS sob diferentes estados básicos de ENOS, sendo identificada propagações de ondas de Rossby a partir da ZCAS aos subtropicos do Hemisfério Norte durante anos de El Niño,destacando a importância dos dutos de oeste na propagação meridional de ondas. Nesta tese foram revelados diferentes guias de ondas de Rossby que interagem com a ZCAS, inclusive guias de ondas interhemisféricos que até então nunca tinham sido relacionados a esta Zona de Convergência Subtropical, este estudo também revela que a ZCAS pode agir como fonte de ondas de Rossby a depender da presença dos dutos de oeste que podem dispersar energia da América do Sul ao Hemisfério Norte, aqui foi demonstrado que esta interação é facilitada durante eventos de El Niño.
Title in English
Atmospheric Rossby Wave Propagations and The South Atlantic Convergence Zone
Keywords in English
ENSO
Rossby Waves
SACZ
Abstract in English
The relationship between the South Atlantic Convergence Zone (SACZ) and Rossby Wave propagation was analyzed over 34 summers, with positive, negative and neutral phases of El Niño Southern Oscillation (ENSO). Zonal and meridional wind components anomalies, calculated based on climatology between 1979-2013 at the level of 200 hPa, were submitted to the Lanczos filter for 20-90 days and 200 days low pass bands, with the intention of highlighting intraseasonal and interannual variability, ensuring three mean compositions of SCAZ referring to the positive, negative and neutral phases of ENSO, through observational analysis of the mean composites of climatological SACZ and positive, negative and neutral phases of ENSO. The analyses in this thesis were divided into two main parts, firstly in relation to the South American domain, to understand the impact of local SACZ, and in the Pacific and South Atlantic Ocean domain, to understand the remote effects associated with this cloud band. From South America in relation to the ENSO phases are highlighted; the suppression of the ITCZ during El Niño years and the intensification of the same during La Niña events; and over the Equatorial Atlantic the north-eastern trough appears to be weakened during La Niña years and intensified during El Niño years, which contributes to the establishment of the Upper Tropospheric Cyclonic Vortex (UTCV). From Pacific Ocean to South America, different Rossby wave guides were revealed that interact with SACZ depending on the interannual variability, during El Niño years the waves are longer and depart from the East Pacific Ocean, close to the South Pacific Convergence Zone region. During La Niñas an interhemispheric Rossby wave train was identified departing from Southeast Asia and dispersing energy to the SACZ with up to 16 days, this Rossby wave pattern was confirmed from numerical simulations using the DREAM (Dynamical Research Empirical Atmospheric Model) baroclinic model. Subsequently, the response of the atmosphere to perturbations in the SACZ region under different basic ENSO states was simulated, and Rossby wave propagation from the SACZ to the subtropics of the Northern Hemisphere was identified during El Niño years, highlighting the importance of the westerly ducts in the meridional wave propagation. In this thesis different Rossby waveguides that interact with the SACZ were revealed, including interhemispheric waveguides that until then have never been related to this Subtropical Convergence Zone, this study also reveals that, the SACZ can act as a source of Rossby waves depending on the presence of the westerly ducts that can disperse energy from South America to the Northern Hemisphere, here it was shown that this interaction is facilitated during El Niño events.
 
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Publishing Date
2022-10-27
 
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