@MastersThesis{Carneiro:2005:AvDeMo,
author = "Carneiro, Gl{\'a}ucia Meira",
title = "O jato em baixos n{\'{\i}}veis na Am{\'e}rica do Sul:
avalia{\c{c}}{\~a}o do desempenho do modelo Eta/CPTEC durante o
SALLJEX",
school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
year = "2005",
address = "S{\~a}o Jos{\'e} dos Campos",
month = "2005-04-01",
keywords = "jato em baixos n{\'{\i}}veis (JBN), SALLJEX, NCEP, modelo Eta,
crit{\'e}rio de bonner, Am{\'e}rica do Sul, Low Level Jet (LLJ),
South American Low Level Jet Experiment (SALLJEX), National Center
for Enveronmental Prediction (NOAA), Eta model, bonner
criterion.",
abstract = "Um dos sistemas meteorol{\'o}gicos que adquiriu maior
import{\^a}ncia nos {\'u}ltimos tempos na Am{\'e}rica do Sul
{\'e}, sem duvida, o Jato de Baixos N{\'{\i}}veis (JBN), devido
a sua influ{\^e}ncia na variabilidade da temperatura, umidade e
precipita{\c{c}}{\~a}o na regi{\~a}o central do continente. Por
esse motivo a comunidade cient{\'{\i}}fica se dedicou a
realiza{\c{c}}{\~a}o de campanhas intensivas de
medi{\c{c}}{\~a}o, como por exemplo, o South American Low Level
Jet Experiment (SALLJEX), com a inten{\c{c}}{\~a}o de mitigar,
pelo menos parcialmente, a grande falta de informa{\c{c}}{\~a}o
na regi{\~a}o de atua{\c{c}}{\~a}o do JBN. Este estudo tem como
principal objetivo realizar uma avalia{\c{c}}{\~a}o da
capacidade do modelo regional Eta/CPTEC em prever e simular os
eventos de JBN. A metodologia utilizada consistiu na
compara{\c{c}}{\~a}o das sa{\'{\i}}das do modelo Eta/CPTEC da
vers{\~a}o operacional (40 km) e da vers{\~a}o experimental (20
km) com os dados de radiossondagem realizados nas
esta{\c{c}}{\~o}es de Santa Cruz, Resistencia e Santiago,
coletados durante o SALLJEX. O estudo se concentrou no
per{\'{\i}}odo 1 a 10 de fevereiro de 2003, o qual esteve
marcado fundamentalmente, pela atua{\c{c}}{\~a}o da baixa
termoorogr{\'a}fica {\`a} leste dos Andes, que permitiu a
acelera{\c{c}}{\~a}o geostr{\'o}fica dos ventos de norte na
regi{\~a}o subtropical. Alguns experimentos num{\'e}ricos
tamb{\'e}m foram realizados com o objetivo de analisar o
poss{\'{\i}}vel impacto de determinados fatores num{\'e}ricos,
como a resolu{\c{c}}{\~a}o horizontal, o tamanho do
dom{\'{\i}}nio de integra{\c{c}}{\~a}o e as
condi{\c{c}}{\~o}es de contorno, nos resultados. Ambas as
vers{\~o}es do modelo conseguiram prever com uma boa
acur{\'a}cia as caracter{\'{\i}}sticas fundamentais dos JBN,
ainda que o modelo Eta de 20 km n{\~a}o tenha fornecido um ganho
significativo nas previs{\~o}es quando comparados com o modelo
Eta 40 km. O modelo tamb{\'e}m conseguiu reproduzir
satisfatoriamente as condi{\c{c}}{\~o}es meteorol{\'o}gicas nos
casos de JBN inativos, embora para a esta{\c{c}}{\~a}o de
Santiago o modelo apresente uma superestimativa da velocidade do
vento meridional. Em geral, n{\~a}o foram detectadas grande
diferen{\c{c}}as no desempenho do modelo para os distintos prazos
de previs{\~a}o, evidenciando um maior {\^e}xito nas
previs{\~o}es superiores a 36 horas de anteced{\^e}ncia, embora,
haja uma subestimativa na condi{\c{c}}{\~a}o inicial obtida
atrav{\'e}s das an{\'a}lises do NCEP. Sendo assim, ressalta-se
que o modelo possui a f{\'{\i}}sica adequada para reproduzir as
caracter{\'{\i}}sticas dos JBN quando a situa{\c{c}}{\~a}o de
escala regional {\'e} suficientemente capturada nas
condi{\c{c}}{\~o}es iniciais. A an{\'a}lise espacial mostrou
novamente um bom desempenho do modelo, visto que o erro m{\'e}dio
e o desvio padr{\~a}o n{\~a}o eram significativos na regi{\~a}o
de atua{\c{c}}{\~a}o do JBN. As diferentes
simula{\c{c}}{\~o}es realizadas com ambas as vers{\~o}es do
modelo Eta/CPTEC mostraram, em geral, que o ganho com a
utiliza{\c{c}}{\~a}o de condi{\c{c}}{\~o}es de contorno
analisadas (an{\'a}lises do NCEP) foi pouco significativo, porque
o fator determinante da qualidade da integra{\c{c}}{\~a}o de
curto prazo s{\~a}o as condi{\c{c}}{\~o}es iniciais comum entre
as rodadas. Atrav{\'e}s do estudo dos campos m{\'e}dios de
temperatura, umidade espec{\'{\i}}fica e transporte de vapor
durante o per{\'{\i}}odo analisado, utilizando as
simula{\c{c}}{\~o}es realizadas com um prazo de 36 horas,
p{\^o}de se comprovar que a atua{\c{c}}{\~a}o do JBN exerce uma
forte influ{\^e}ncia sobre a variabilidade da
precipita{\c{c}}{\~a}o na regi{\~a}o subtropical da
Am{\'e}rica do Sul, {\`a} leste dos Andes, incluindo a
Regi{\~a}o Sul do Brasil, Bol{\'{\i}}via, Paraguai, Uruguai e
norte da Argentina. ABSTRACT: One of the meteorological systems
that acquired great importance in South America during the last
years is, undoubtedly, the Low Level Jet (LLJ), mostly due to its
probable influence on the temperature, humidity and precipitation
variability on the central region of the continent. The major
attention that the scientific community gave to this system
motivated the organization of intensive measure campaigns, as the
experiment SALLJEX, tending to reduce at least partially, the lack
of information in the LLJ region. The main objective of this study
is to perform an evaluation of the ability of the Eta/CPTEC
regional model to forecast and simulate some events of LLJ. To
this purpose comparisons between model outputs (an operational
version (40km) and a experimental one (20 km)) and radiosonde data
collected at Santa Cruz, Resistencia and Santiago stations, during
the SALLJEX were done. The work was concentrated in the period
from February, 1st to February, 10th, 2003, which was
characterize, for the presence of the thermal-orographic low to
the east of Andes that allowed a geotrophic acceleration of
northerly winds on the subtropical region. Some experiments has
been performed in order to analyze the possible impact of some
numeric factors into results, such as the horizontal resolution,
the size of the integration domain and the boundary conditions.
Both model versions succeeded in accurately forecasting/simulating
the main features of the LLJ. The Eta 20 km version did not show a
significant forecast improvement when compared to the Eta 40 km.
Eta Model was also successful in reproducing the meteorological
conditions in the cases of inactive LLJ, although it showed a
slight tendency to overestimate the southern wind at Santiago
station. In general model performance was relatively independent
of the forecast lead times, even showing e slight improvement when
the forecast lead-time was greater than 36 hours. This fact is
possibly influenced by the systematic underestimation of the NCEP
analysis, used as initial condition. Results make evident that the
Eta model has an adequate physical package in order to reproduce
the main features of the LLJ, if the regional scale meteorological
situation is corrected captured by the initial conditions. The
horizontal variability of the LLJ was also well captured by the
model since mean and standard errors were no significant in the
region affected by the LLJ. Both 40km and 20 km Eta/CPTEC model
simulations showed that the use of analyzed boundary conditions
(NCEP) did not cause a significant impact. Studying the mean
fields of temperature, specific humidity and humidity transport
during the analyzed period, it is possible to conclude that LLJ
has a strong influence on the precipitation variability in the
subtropical South America, to the east of the Andes, including the
Southern Brazil, Bolivia, Paraguay, Uruguay and north of
Argentina.",
committee = "Orsini, Jos{\'e} Antonio Marengo (presidente) and Nobre, Carlos
Afonso (orientador) and Seluchi, Marcelo Enrique and Chan, Chou
Sin and Ambrizzi, T{\'e}rcio",
copyholder = "SID/SCD",
englishtitle = "The low level jet in South American: valuation of the Eta/CPTEC
model performance during the SALLJEX",
language = "pt",
pages = "129",
ibi = "6qtX3pFwXQZ3P8SECKy/Gta8b",
url = "http://urlib.net/ibi/6qtX3pFwXQZ3P8SECKy/Gta8b",
targetfile = "paginadeacesso.html",
urlaccessdate = "21 maio 2024"
}