INVESTIGADORES
MÜLLER Gabriela Viviana
artículos
Título:
Mean Atmospheric Circulation Leading to Generalized Frosts in Central Southern South America
Autor/es:
MÜLLER GABRIELA V; AMBRIZZI, TÉRCIO; NUÑEZ, MARIO
Revista:
Theoretical and Applied Climatology
Editorial:
Springer Link
Referencias:
Año: 2005 vol. 82 p. 95 - 112
ISSN:
0177-798X
Resumen:
The purpose of this study is to analyze the atmospheric
circulation patterns associated to extreme frost episodes
which affect the extensive region known as the Wet Pampas
in the center-south of South America during the 19611990
period. The years with an extreme frequency of generalized
frost are identified by selecting the cases beyond one
standard deviation above and below the average of the
corresponding period. Two groups were formed: one for
the years with events above the average (þs) and the other
with those below the average (s). The years of generalized
frosts were separated into the periods from May to
September, June to August and individual months.
From the comparison between the composite of the two
groups (þs and s), it was possible to determine that the
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
frosts were separated into the periods from May to
September, June to August and individual months.
From the comparison between the composite of the two
groups (þs and s), it was possible to determine that the
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
frosts were separated into the periods from May to
September, June to August and individual months.
From the comparison between the composite of the two
groups (þs and s), it was possible to determine that the
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
frosts were separated into the periods from May to
September, June to August and individual months.
From the comparison between the composite of the two
groups (þs and s), it was possible to determine that the
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
frosts were separated into the periods from May to
September, June to August and individual months.
From the comparison between the composite of the two
groups (þs and s), it was possible to determine that the
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mid-latitude
wave was observed at higher levels with a large-amplitude
trough over SouthAmerica extending to tropical latitudes
and a progressive amplification from another trough located
upstream in the Pacific Ocean.
The analysis of the different periods confirmed the relationship
between the intensification of the subtropical jet
in South America and the higher frequency of generalized
frosts. The intensification of the jet may be related to an
amplification of the pressure gradient in the region due to
the increase in Rossby wave activity.
anomaly fields are opposite in almost all the periods studied.
In the seasonal composites of generalized frosts below average,
the circulation field presented a barotropic structure with
an anomalous cyclonic persistence over the south-west of
South America and a weak subtropical jet over the continent.
On the other hand, the structure and evolution of the systems
that produce generalized frosts in extremely cold winters
were analyzed by calculating the composites of the daily
fields from these episodes. The results showed that the incursion
of cold air in the lower levels begins with a migratory
anticyclone moving from the south-east Pacific to the south
of the continent and a deepening of an anomalous low pressure
center over the south-east of the Argentine Atlantic
coast. Both systems cause cold, dry air advection from the
south, with a reduction in temperature over the center and
eastern parts of the country. The development of a mi