@InProceedings{MattosCoel:2013:DiCoAt,
author = "Mattos, Ariane Frassoni dos Santos de and Coelho, Caio Augusto dos
Santos",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto
Nacional de Pesquisas Espaciais (INPE)}",
title = "Diagn{\'o}stico das condi{\c{c}}{\~o}es atmosf{\'e}ricas
previstas pelo MCGA/CPTEC para a estiagem na Regi{\~a}o Nordeste
do Brasil durante o trimestre de MAM de 2013/ Diagnosing
CPTEC/AGCM atmospheric condition predictions for the Northeast
Brazil MAM 2013 drought episode",
booktitle = "Anais...",
year = "2013",
organization = "Simp{\'o}sio Internacional de Climatologia, 5. (SIC).",
keywords = "Seasonal climate forecasting, AGCM/CPTEC, Northeast Brazil.",
abstract = "RESUMO: A Regi{\~a}o Nordeste do Brasil {\'e} tipicamente
afetada pela ocorr{\^e}ncia de eventos de seca, principalmente
devido {\`a} distribui{\c{c}}{\~a}o irregular dos regimes de
chuvas e por localizase em regi{\~a}o de clima semi{\'a}rido.
Altera{\c{c}}{\~o}es nos padr{\~o}es atmosf{\'e}ricos podem
afetar a qualidade dos diferentes regimes chuvosos na Regi{\~a}o,
gerando per{\'{\i}}odos de secas prolongados. Desde meados de
2012 uma persistente condi{\c{c}}{\~a}o de estiagem vem sendo
observada na Regi{\~a}o Nordeste do Brasil. Esta
situa{\c{c}}{\~a}o tamb{\'e}m tem persistido ao longo do ano de
2013. O Centro de Previs{\~a}o de Previs{\~a}o de Tempo e
Estudos Clim{\'a}ticos (CPTEC) do Instituto Nacional de Pesquisas
Espaciais (INPE) realiza rotineiramente a previs{\~a}o
clim{\'a}tica sazonal utilizando o Modelo de
Circula{\c{c}}{\~a}o Geral da Atmosfera (MCGA/CPTEC). O modelo
{\'e} integrado com quinze condi{\c{c}}{\~o}es iniciais
distintas, tr{\^e}s diferentes esquemas de
parametriza{\c{c}}{\~a}o convectiva e duas condi{\c{c}}{\~o}es
de contorno, a saber: anomalia de temperatura do mar (TSM)
persistida e anomalia de TSM previsa pelo modelo acoplado
OceanoAtmosfera do National Centers for Environmental Prediction,
National Center for Atmospheric Research, gerando um conjunto de
90 membros (realiza{\c{c}}{\~o}es). As previs{\~o}es do
MCGA/CPTEC v{\^e}m indicando d{\'e}ficit de
precipita{\c{c}}{\~a}o para a Regi{\~a}o Nordeste do Brasil,
sendo tais previs{\~o}es condizentes com os padr{\~o}es que
v{\^e}m sendo observados ao longo dos anos de 2012 e 2013. O
presente trabalho tem como objetivo avaliar as previs{\~o}es
clim{\'a}ticas sazonais produzidas pelo MCGA/CPTEC em reproduzir
as caracter{\'{\i}}sticas atmosf{\'e}ricas de grande escala
associadas {\`a}s condi{\c{c}}{\~o}es de seca ocorridas na
Regi{\~a}o Nordeste do Brasil durante o trimestre de
mar{\c{c}}o, abril e maio de 2013 (MAM/2013). O trimestre em
considera{\c{c}}{\~a}o {\'e} um dos mais importantes em termos
de distribui{\c{c}}{\~a}o de chuva, sendo observados elevados
volumes pluviom{\'e}tricos em grande parte a Regi{\~a}o
Nordeste, em particular no setor norte. Para este estudo, foram
analisados campos de vento em baixos e altos n{\'{\i}}veis,
umidade espec{\'{\i}}fica, velocidade vertical e
precipita{\c{c}}{\~a}o do conjunto de previs{\~o}es do
MCGA/CPTEC. Tanto a anomalia de TSM persistida do m{\^e}s de
Janeiro de 2013quanto as anomalias de TSM previstas para o meses
de Fevereiro a Maio de 2013, ambas utilizadas como
condi{\c{c}}{\~o}es de contorno para o MCGA/CPTEC, indicavam o
predom{\'{\i}}nio de anomalias positivas de TSM no Oceano
Atl{\^a}ntico tropical norte e condi{\c{c}}{\~o}es variando de
normal a ligeiramente abaixo da normal climatol{\'o}gica no
Oceano Atl{\^a}ntico tropical sul. Os campos de anomalia de
circula{\c{c}}{\~a}o em altos n{\'{\i}}veis previstos pelo
MCGA/CPTEC indicaram a predomin{\^a}ncia de um cavado cujo eixo
se posicionou sobre a Regi{\~a}o Nordeste do Brasil. Em baixos
n{\'{\i}}veis, prevaleceu uma circula{\c{c}}{\~a}o
anticicl{\^o}nica an{\^o}mala centrada sobre o Oceano
Atl{\^a}ntico, pr{\'o}ximo {\`a} costa da Regi{\~a}o Sudeste,
gerando uma circula{\c{c}}{\~a}o anticicl{\^o}nica
perpendicular {\`a} costa da Regi{\~a}o Nordeste. Este
padr{\~a}o poderia favorecer o aumento da umidade na regi{\~a}o
litor{\^a}nea da Regi{\~a}o, por{\'e}m, de acordo com o campo
de movimento vertical em 500 hPa previsto pelo modelo, o
predom{\'{\i}}nio de movimentos descendentes sobre a Regi{\~a}o
contribuiu para a aus{\^e}ncia de convec{\c{c}}{\~a}o e
anomalias negativas de precipita{\c{c}}{\~a}o. Este padr{\~a}o
an{\^o}malo foi identificado em todas as vers{\~o}es do
MCGA/CPTEC, por{\'e}m, com mais intensidade nas vers{\~o}es cuja
condi{\c{c}}{\~a}o de contorno {\'e} a anomalia de TSM
prevista. Este mecanismo esteve associado {\`a} resposta
atmosf{\'e}rica ao padr{\~a}o de aquecimento na regi{\~a}o do
Oceano Atl{\^a}ntico tropical norte, gerando uma c{\'e}lula de
circula{\c{c}}{\~a}o local do tipo Hadley sobre a Regi{\~a}o
Nordeste do Brasil. Tamb{\'e}m, a previs{\~a}o do modelo indicou
anomalia negativa de umidade espec{\'{\i}}fica, padr{\~a}o este
mais intenso tamb{\'e}m nas vers{\~o}es com TSM prevista. Este
padr{\~a}o sugere uma poss{\'{\i}}vel resposta {\`a}
subsid{\^e}ncia compensat{\'o}ria da c{\'e}lula local de
Hadley, que favorece a subsid{\^e}ncia de ar seco sobre a
Regi{\~a}o Nordeste, proveniente dos altos n{\'{\i}}veis da
atmosfera. ABSTRACT: The Northeast region of Brazil is typically
affected by the occurrence of drought events, mainly due to the
uneven rainfall distribution regime and for being located in a
semiarid climatic region. Atmospheric pattern changes can affect
the quality of different rainfall regimes, particularly during the
rainy season over Northeast Brazil, producing long periods of
drought. Since mid2012 persistent drought conditions have been
observed in Northeastern Brazil. This characteristic has also
persisted throughout 2013. The Center for Weather Forecasting and
Climate Studies (CPTEC) of the National Institute for Space
Research (INPE) routinely performs seasonal climate forecasts with
the Atmospheric General Circulation Model (AGCM). The AGCM/CPTEC
is integrated with fifteen different initial conditions, three
different convective parameterization schemes and two boundary
conditions: persisted sea surface temperature (SST) anomaly and
forecast SST by the coupled oceanatmosphere model of the National
Centers for Environmental Prediction, National Center for
Atmospheric Research (NCEP/NCAR), generating an ensemble of 90
members. The AGCM/CPTEC forecasts have consistently indicated
rainfall deficit for Northeast Brazil, and such forecasts are
consistent with observed patterns since 2012 and mid2013. This
study aims to evaluate the ability of AGCM/CPTEC in reproducing
the largescale atmospheric features associated with drought
conditions occurred in Northeastern Brazil during March, April and
May 2013 (MAM/2013). This period is one of the most important in
terms of rainfall distribution, when expressive rainfall volumes
are observed over most Northeast, particularly in the north
portion of this region. In this study, wind fields at low and
upperlevels, specific humidity, vertical velocity and
precipitation ensemble forecasts are analyzed. Both January 2013
persisted SST anomalies and February to May 2013 forecast SST
anomalies boundary conditions indicated warmer than normal
conditions over tropical North Atlantic Ocean, and also indicated
conditions ranging from normal to slightly below normal in the
tropical South Atlantic Ocean. The forecasted upperlevel
circulation anomaly indicated a trough over Northeast Brazil. At
lowlevels, the forecast showed a prevailing anomalous anticyclonic
circulation centered over the South Atlantic Ocean, near the
Southeast coast of Brazil, generated an anticyclonic circulation
perpendicular to the Northeast coast of Brazil. This pattern could
have favored increased humidity availability in the coastal area.
However, the vertical motion forecast at 500 hPa revealed
prevailing downward air motion over the region, contributing to
convective activity suppression and the forecast consistently
indicated negative precipitation anomalies over Northeast Brazil.
This anomalous precipitation forecast pattern was identified in
all versions of the AGCM/CPTEC, but presented the most intense
anomalies in model versions forced with forecast SST anomalies.
The mechanism for the forecast precipitation deficit is the
atmospheric response to warmer than normal oceanic conditions over
the tropical North Atlantic ocean, generating a local Hadley Cell,
with ascending air motion over the ocean and descending air motion
over Northeast Brazil. The model forecast also indicated negative
specific humidity anomalies over this region, a feature that was
also more intense in the forecasts produced with forecast SST
anomalies as boundary conditions. This pattern is suggested to be
a possible compensatory response to the subsidence branch of the
Hadley Cell, which favors upperlevels dry air subsidence over the
Northeast region of Brazil.",
conference-location = "Florian{\'o}polis, SC",
conference-year = "15-19, set.",
urlaccessdate = "16 jun. 2024"
}