The Antarctic connection to cold and warm anomalies in So. Brazil
Setzer, A.W.1, Romão, M.O.1 and Aquino, F.E.2
1CPTEC\INPE
- Center for Numerical Weather Forecast and Climate Studies, National
Space Institute of Brazil
2CPC\UFRGS – Climate and Polar Center, Federal University of Rio Grande do Sul,
Brazil.
Neglected phenomena:
Direct exchanges of air
masses between
Antarctica and South
America tropical and
equatorial latitudes
occur at the surface
level, on both ways.
Main implications:
weather, atmospheric
chemistry, biological
exchanges, Antarctic
contamination, etc...
North to South - Emissions from vegetation fires in Amazonia are
transported southward, eventually reaching the Brazilian
Antarctic Station, 6,000 km away.
South to North Antarctic Outflow
Masses of cold air from the Bellingshausen and
Weddell seas occasionally propagate northwards at
surface level, reaching the coastal tropical latitudes
of Brazil and causing low temperatures, precipitation,
and snow in high mountains.
Resulting monthly anomalies for surface air
temperature in south Brazil vary from - 1oC to - 3.5oC.
The summer of 2004, so far the season with more SNC
days, was the coldest on record for the last 45 years at
Rio de Janeiro.
On 20/Jun/2005, the SNC reached the latitude of
~15oS, thus propagating over more than 8,000 km
from ~85oS.
Austral Summer
2003-04:
Antarctic wind
anomalies affected
the climate in S & SE
Brazil
The coldest summer
in 39 years
Air Temperature: monthly surface anomalies, summer 2003-04
Dec/03, – 3oC
Jan/04, – 2oC
Feb/04, – 2oC
Mar/04, – 1oC
Wind vector: monthly surface anomalies, summer 2003-04
Dez/03, – 6 m/s, Drake(reversal!)
Feb/04, from Weddell N to S Brasil
Jan/04, up to + 6 m/s
Mar/04, from Weddell N to S Brasil
1st. Semester/2004 in S & SE Brasil: the coldest in decades
Examples for May/2004.
Example of the air outflow from the
Weddell Sea until S and SE of Brazil,
from 16-19/May/2004, at surface level
bringing lower air temperatures and
more precipitation.
Wind vector at 300 hPa showing
intense and abnormal northward air
flow from the N Weddell Sea and
Antarctic Peninsula S Brazil
The anomalies in temperature and wind occurred with changes
in the jet stream pattern at 300 hPa: average February, 19682003, average Feb/2004 and anomaly Feb/2004
The unique circulation South-to-North from the Weddell Sea to the
South American east coast plays an important role in the regional
climate. Wind Vector at 925 hPa.
19/June/2005
20/June/2005
Wind Vector at 925 hPa. Note strong circulation South=>North
from Weddell Sea to the South American east coast
21/june/2005
22/june/2005
Surface weather chart for
20/June/2005 12 Z
Note the South-to-North
circulation from the Sea of
Weddell to the S and SE
coast of Brazil
Surface weather chart for
21/June/2005 12 Z
Note the South-to-North
circulation from the Sea of
Weddell to the S and SE
coast of Brazil
Trajectory analysis also confirms (within its limitations) the
northward trajectory of the air masses from the Weddell Sea.
12o S
11 & 12/September/2005: again, South-to-North surface Antarctic wet
circulation, causing air temperature decrease (10oC in 24h) an
precipitation (snow and freezing rain for many counties in the Brazilian
southern states of RS and SC.
Freezing rain at São
Joaquim, SC, 11/Set/2005
(Source: Jornal A Notícia)
This Antarctic outflow is
always humid because it
absorbs moisture while
propagating over warmer
Atlantic waters, causing
overcast skies and
precipitation.
These are opposite
conditions to those for frosts,
when skies are clear and the
atmosphere dry under strong
anticiclones.
Basic synoptic configuration for the S-N Antarctic outflow
Operational
alerts have
been issued
with numerical
forecast
products at
CPTEC/INPE,
based on the
synoptic set up
associated to
the S-N flow.
South-North Antarctic outflow reaching at least 30oS
An open question
South-North Antarctic Outflow to South America
• Unique meteorological phenomenon: Antarctic air from high
latitudes reaches S and SE Brazil, convering up to 70o of
latitude (~7.000 km !) at surface level from south to north,
with an average speed of ~15 m/s (~50 km/h).
• Marked effects in the temperature and precitipation, mainly
at the south and southeast coast.
• Its duration affects the temperature in the S and SE of Brazil:
2004 was the coldest summers in the last decades, and 2005
one of the warmest..
• Phenomena not yet understood and used in weather
forecasting and modelling..
Endereços contendo publicações
sobre circulação S-N
• http://www.cptec.inpe.br/prod_antartica/publicacoes/200
509_setzer_romao_spaxiii_continente.pdf
• http://www.cptec.inpe.br/prod_antartica/publicacoes/200
111_aquino_dewes_setzer_spa_x_nevesul.pdf
• http://www.cptec.inpe.br/prod_antartica/publicacoes/200
410_romao_setzer_spaxii_verao2003_04.pdf
• http://www.cptec.inpe.br/prod_antartica/publicacoes/200
605_aquino_setzer_viana_romao_encontro_ufrgs_quadr
oclimatico.pdf
• http://www.cptec.inpe.br/prod_antartica/publicacoes/200
611_aquino_setzer_simoes_14sbmet_3112.pdf
• http://www.cptec.inpe.br/prod_antartica/publicacoes/200
610_aquino_setzer_romao_14spa_conexoes.pdf