@PhDThesis{Antunes:2018:EsOnGr,
author = "Antunes, Cassio Espindola",
title = "Estudo de ondas de gravidade-ac{\'u}stica observadas na MLT sobre
a regi{\~a}o Amaz{\^o}nica e no Sul do Brasil",
school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
year = "2018",
address = "S{\~a}o Jos{\'e} dos Campos",
month = "2018-05-30",
keywords = "ondas de gravidade-ac{\'u}stica, fontes de gera{\c{c}}{\~a}o de
ondas de gravidade ac{\'u}stica, luminesc{\^e}ncia
atmosf{\'e}rica, simula{\c{c}}{\~o}es num{\'e}ricas, frentes
mesosf{\'e}ricas, acoustic gravity waves, acoustic gravity waves
sources, agrilow, numeric simulations, mesospheric bores.",
abstract = "Neste trabalho s{\~a}o investigadas as caracter{\'{\i}}sticas
das ondas de gravidade na alta atmosfera sobre duas regi{\~o}es
distintas do Brasil. Foram analisados dados da luminesc{\^e}ncia
atmosf{\'e}rica na MLT (Mesosphere and Lower Thermosphere), das
emiss{\~o}es do OI 557,7 nm e NaD 589,3 nm, obtidos por um
imageador all-sky. A esta{\c{c}}{\~a}o SMS (29,442S; 53,822O)
fica localizada no extremo sul do Brasil, entre baixas e
m{\'e}dias latitudes, na cidade de S{\~a}o Martinho da Serra,
RS. Os dados analisados foram coletados entre mar{\c{c}}o de 2011
a maio de 2012. Nos eventos analisados neste s{\'{\i}}tio
observou-se uma anisotropia na dire{\c{c}}{\~a}o de
propaga{\c{c}}{\~a}o em torno do eixo NO-SE. A
propaga{\c{c}}{\~a}o preferencial no inverno foi para NO,
enquanto que no ver{\~a}o ocorreu no sentido SE. A
esta{\c{c}}{\~a}o MAN (2,589S; 60,221O) fica na regi{\~a}o
Norte do Brasil em meio a floresta Amaz{\^o}nica, a cerca de 60
km de Manaus, AM. Os dados analisados para este s{\'{\i}}tio
compreendem o per{\'{\i}}odo de julho de 2015 a agosto de 2017.
Somente no per{\'{\i}}odo do outono observou-se uma
dire{\c{c}}{\~a}o preferencial para N na propaga{\c{c}}{\~a}o
das ondas de gravidade. Nas demais esta{\c{c}}{\~o}es do ano
n{\~a}o houve dire{\c{c}}{\~a}o preferencial, sendo que no
inverno, per{\'{\i}}odo com maior n{\'u}mero de
observa{\c{c}}{\~o}es, a propaga{\c{c}}{\~a}o foi quase
isotr{\'o}pica. Frentes mesosf{\'e}ricas foram observadas em
ambas regi{\~o}es e estudo de casos abordando este tipo de evento
s{\~a}o apresentados. Duas frentes mesosf{\'e}ricas duplas (twin
mesospheric bores) foram observadas na esta{\c{c}}{\~a}o MAN.
Mais de 50% dos eventos observados em SMS n{\~a}o tem
rela{\c{c}}{\~a}o com atividade convectiva na troposfera,
sugerindo que as fontes est{\~a}o acima dessa regi{\~a}o. Sobre
a esta{\c{c}}{\~a}o MAN a atividade convectiva troposf{\'e}rica
{\'e} praticamente cont{\'{\i}}nua ao longo do ano, sendo
tipicamente observadas m{\'u}ltiplas zonas de
convec{\c{c}}{\~a}o na regi{\~a}o Amaz{\^o}nica. A
posi{\c{c}}{\~a}o destas zonas de convec{\c{c}}{\~a}o
troposf{\'e}ricas apresentou alta correla{\c{c}}{\~a}o com a
dire{\c{c}}{\~a}o de propaga{\c{c}}{\~a}o das ondas de
gravidade observadas na MLT. Um novo mecanismo de
gera{\c{c}}{\~a}o de ondas de gravidade-ac{\'u}stica in situ na
baixa termosfera, devido a aquecimento Joule associado {\`a}s
camadas E-espor{\'a}dicas foi proposto. Simula{\c{c}}{\~o}es
num{\'e}ricas da gera{\c{c}}{\~a}o e propaga{\c{c}}{\~a}o de
ondas de gravidade-ac{\'u}stica foram conduzidas para o mecanismo
proposto e para m{\'u}ltiplas for{\c{c}}antes
troposf{\'e}ricas. ABSTRACT: In this work is presented an
investigation of gravity waves observed in the upper atmosphere
over two distinct regions of Brazil. Nightime airglow data
emissions of the OI 557.7 nm and NaD 589.3 nm from the MLT
Mesosphere and Lower Thermosphere, obtained by an all-sky imager
are analyzed. The SMS station (29.442S, 53.822W) is located in the
Southern Brazil, between low and middle latitudes, in the city of
S{\~a}o Martinho da Serra, RS state. The data were collected from
March 2011 to May 2012. An anisotropy was observed in the
propagation direction NW-SE for the events analyzed at SMS
station. The preferential propagation in the winter was to NW,
whereas in the summer it occurred in the SE direction. The MAN
station (2.589S, 60.221W) is in the Northern Brazil in the Amazon
forest region, located about 60 km from Manaus, AM state. The MAN
analyzed data comprise the period from July 2015 to August 2017. A
northward preferential propagation was observed during fall period
while during the other seasons there was no preferential
direction. In the winter, the period with the highest number of
observations, the propagation was almost isotropic. Mesospheric
fronts were observed in both regions and studies addressing this
type of event are presented. Two double mesospheric bores (twin
mesospheric bores) were observed at the MAN station. Investigation
of possible sources indicated that more than 50 % of the events
observed in SMS have no evident relation with convective ativity,
therefore probably have their sources above the troposphere. On
the other hand, the tropospheric convective activity is
practically continuous throughout the year on the MAN station,
being usual to observe multiple convection zones in the Amazon
region. These tropospheric convection zones position showed a high
correlation with the propagation direction of gravity waves
observed in the MLT. A new mechanism for acoustic gravity wave
generation in the low thermosphere due to Joule heating associated
with E-sporadic layers is proposed. Numerical simulations of
acoustic gravity waves generation and propagation were conducted
for the proposed in situ generation mechanism and for multiple
tropospheric forcing.",
committee = "Dal Lago, Alisson (presidente) and Pimenta, Alexandre Alvares
(orientador) and Silva, V{\^a}nia F{\'a}tima Andrioli Novaes
(orientador) and De Nardin, Clezio Marcos and Fagundes, Paulo
Roberto and Guede, Jos{\'e} Ricardo Abalde",
englishtitle = "Study of acoustic gravity waves observed in the MLT over the
Amazonic region and in the Southern Brazil",
language = "pt",
pages = "179",
ibi = "8JMKD3MGP3W34R/3R453E8",
url = "http://urlib.net/ibi/8JMKD3MGP3W34R/3R453E8",
targetfile = "publicacao.pdf",
urlaccessdate = "19 abr. 2024"
}