@PhDThesis{Figueroa:1997:EsSiCi,
author = "Figueroa, Silvio Nilo",
title = "Estudo dos sistemas de circula{\c{c}}{\~a}o de ver{\~a}o sobre
a Am{\'e}rica do Sul e suas simula{\c{c}}{\~o}es com modelos
num{\'e}ricos",
school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
year = "1997",
address = "Sao Jose dos Campos",
month = "1997-08-15",
keywords = "estudo do tempo e clima, Am{\'e}rica do Sul, Alta da
Bol{\'{\i}}via, zona de converg{\^e}ncia do Atl{\^a}ntico Sul,
v{\'o}rtices cicl{\^o}nicos, modelos atmosf{\'e}ricos.",
abstract = "Neste trabalho, realizou-se um estudo observacional e de modelagem
dos sistemas de circula{\c{c}}{\~a}o de ver{\~a}o sobre a
Am{\'e}rica do Sul (AS): Zona de Converg{\^e}ncia do
Atl{\^a}ntico Sul (ZCAS), Alta da Bol{\'{\i}}via (AB), Vortice
Cicl{\^o}nico (VC) e a Zona de Converg{\^e}ncia Intertropical
(ZCIT). Utilizou-se Fun{\c{c}}{\~o}es Ortogonais
Emp{\'{\i}}ricas (EOF) com os dados de vorticidade relativa para
17 ver{\~o}es, e modelos num{\'e}ricos (modelo de
circula{\c{c}}{\~a}o geral e modelo de {\'a}rea limitada). Os
resultados mostram que a forma{\c{c}}{\~a}o da ZCAS n{\~a}o
depende dos Andes, da ZCIT, da convec{\c{c}}{\~a}o da
{\'A}frica e da Zona de Converg{\^e}ncia do Pac{\'{\i}}fico
Sul (ZCPS). Entretanto, na aus{\^e}ncia de convec{\c{c}}{\~a}o
tropical sobre a AS, a ZCAS n{\~a}o se forma. Os Andes s{\~a}o
respons{\'a}veis pela localiza{\c{c}}{\~a}o da m{\'a}xima
precipita{\c{c}}{\~a}o observada durante o ver{\~a}o entre 60
degrees e 50 degrees W e em torno de 10 degrees S. Na
aus{\^e}ncia dos Andes, esta zona de m{\'a}xima
precipita{\c{c}}{\~a}o localiza-se pr{\'o}ximo ao Equador,
entre 60 degrees e 50 degrees W e em torno de 2,5 degrees S.
Portanto, os Andes influenciam indiretamente no posicionamento e
na intensifica{\c{c}}{\~a}o da ZCAS atrav{\'e}s da
localiza{\c{c}}{\~a}o e intensifica{\c{c}}{\~a}o da
m{\'a}xima precipita{\c{c}}{\~a}o sobre a parte central da AS.
A aus{\^e}ncia da convec{\c{c}}{\~a}o da ZCIT favorece a
ocorr{\^e}ncia de precipita{\c{c}}{\~a}o na regi{\~a}o sul do
Nordeste. As ondas transientes de n{\'u}meros de onda zonal 5 e 6
e com per{\'{\i}}odos de 8 a 10 dias tem influ{\^e}ncia na
ZCAS. Portanto, para a forma{\c{c}}{\~a}o e
manuten{\c{c}}{\~a}o da ZCAS {\'e} importante a
intera{\c{c}}{\~a}o entre a convec{\c{c}}{\~a}o tropical sobre
a AS e as ondas transientes de n{\'u}meros de onda zonal 5 e 6,
sendo os Andes, a ZCIT e a convec{\c{c}}{\~a}o da {\'A}frica
fatores secund{\'a}rios. Por{\'e}m, existem outros fatores que
modulam a variabilidade intrasazonal da ZCAS. Estas s{\~a}o, as
oscila{\c{c}}{\~o}es de 20-30 dias (per{\'{\i}}odo m{\'e}dio
de 22 dias) e de 30-60 dias (per{\'{\i}}odo m{\'e}dio de 42
dias). Estas oscila{\c{c}}{\~o}es tamb{\'e}m est{\~a}o
associadas {\`a} teleconex{\~a}o entre a ZCPS e a ZCAS. A
forma{\c{c}}{\~a}o e manuten{\c{c}}{\~a}o do VC
quase-estacion{\'a}rio (VCQ) pr{\'o}ximo ao Nordeste deve-se
{\`a} presen{\c{c}}a da ZCAS. Os sistemas de
circula{\c{c}}{\~a}o AB, ZCAS e VCQ constituem um sistema
acoplado quase-estacion{\'a}rio (SAQE). Este sistema acoplado
pode existir na aus{\^e}ncia da ZCIT. Entretanto, a ZCIT do
Atl{\^a}ntico tem influ{\^e}ncia na intensifica{\c{c}}{\~a}o
do SAQE. Neste sistema acoplado, o VCQ depende da ZCAS, a AB
depende da convec{\c{c}}{\~a}o da Amaz{\^o}nia e da ZCAS, a
ZCAS depende da convec{\c{c}}{\~a}o da Amaz{\^o}nia e dos
transientes de latitudes m{\'e}dias, e a convec{\c{c}}{\~a}o da
Amaz{\^o}nia depende de fatores de grande escala. Mas existe
tamb{\'e}m uma intera{\c{c}}{\~a}o entre cada um dos
componentes deste sistema, contribuindo para manter o SAQE por
v{\'a}rios dias. Por outro lado, a g{\^e}nese dos v{\'o}rtices
cicl{\^o}nicos transientes (VCT) sobre o Atl{\^a}ntico Sul
deve-se {\`a} libera{\c{c}}{\~a}o de calor latente em torno da
Bahia, ao sul do Nordeste. ABSTRACT: This work presents an
observational and modeling study of the Southern Hemisphere (SH)
summer circulation systems over South America, namely, the South
Atlantic Convergence Zone (SACZ), the Bolivian High (BH), Cyclonic
Vortices (CV), and the Intertropical Convergence Zone (ITCZ). EOF
analysis was used in the observational part to analyze relative
vorticity data for 17 SH summer periods. In the modeling part,
both Global Circulation and Limited Area Models were used. The
results indicate that the establishment of the SACZ does not
depend on the Andes Mountains or on the ITCZ or on African
convection, or on the South Pacific Convergence Zone (SPCZ).
However, the SACZ does not establish itself with absence of
tropical convection over South America. The Andes Mountains seem
to be responsible for the placement of the SH summer rainfall
maxima around 50o-60oW and 10oS. In a simulation without the Andes
Mountains, the rainfall maxima is displaced equatorward to 2.5oS.
Therefore, the Andes Mountains affect indirectly the position and
intensification of the SACZ through anchoring the rainfall maxima
over central tropical South America. Weak or no convection over
the ITCZ favors precipitation over southern Northeast Brazil.
Transient waves with zonal wave numbers 5 and 6 and period of 8-10
days influence the SACZ. In sum, the main factor for the
establishment and maintenance of the SACZ is the interaction
between tropical convection over South America and the transient
waves with zonal wave numbers 5 and 6. The Andes Mountains, ITCZ
and African convection are secondary in importance for the SACZ.
However, there are other factors which modulate the intraseasonal
variability of the SACZ. There are 20-30-day (average period 22
days) and 30-60-day oscillations (average period 42 days) sweeping
through the SACZ region. These oscillations are also associated
with teleconnection between the SPCZ and the SACZ. The formation
and maintenance of the quasi-stationary CV (QCV) over the tropical
South Atlantic in the vicinity of Northeast Brazil is directly
related to the SACZ. The circulation systems BH, SACZ and QCV
constitute a tightly linked, quasi-stationary system. This system
can exist independent of the Atlantic ITCZ, but its
intensification is related to the Atlantic ITCZ. In this system
the QCV depends on the SACZ, the BH depends on Amazon convection
and on convection over the SACZ, the SACZ depends on Amazon
convection and midlatitude transient disturbances, and, lastly,
Amazon convection depends on large scale factors. Additionally
there exist interactions among the components of this system
(BH-SACZ-QCV) which contribute to maintaining the system for
several days. On the other hand, the genesis of transient CV (TVC)
is associated to the release of latent heat in southern Northeast
Brazil (Bahia region).",
committee = "Bonatti, Jos{\'e} Paulo (presidente) and Nobre, Carlos Afonso
(orientador) and Kayano, Mary Toshie and Rao, Vadlamudi
Brahmananda and Dias, Pedro Leite da Silva and Grimm, Alice
Marlene",
copyholder = "SID/SCD",
englishtitle = "Observational and modeling study of the summer circulation systems
over South America",
label = "8469",
language = "pt",
pages = "201",
ibi = "6qtX3pFwXQZ4PKzA/hsMyo",
url = "http://urlib.net/ibi/6qtX3pFwXQZ4PKzA/hsMyo",
targetfile = "publicacao.pdf",
urlaccessdate = "09 maio 2024"
}