CICYTTP   12500
CENTRO DE INVESTIGACION CIENTIFICA Y DE TRANSFERENCIA TECNOLOGICA A LA PRODUCCION
Unidad Ejecutora - UE
artículos
Título:
Teleconnection Patterns and Rossby Wave Propagation Associated to Generalized Frosts over Southern South America
Autor/es:
MULLER, GABRIELA VIVIANA
Revista:
Climate Dynamics
Referencias:
Año: 2007 vol. 29 p. 1432 - 1894
ISSN:
1432-0894
Resumen:
Based on previous observational studies of the
mean atmospheric circulation leading to generalized frosts
(GF) in central Southern South America, it is possible to
establish a hypothesis that specific large scale patterns are
associated to the frequency of occurrence of these events
through the propagation of Rossby waves remotely excited.
This hypothesis is tested here through a teleconnection
analysis for austral winters which present an extreme frequency
of occurrence of GF in southeastern South America,
particularly over the Wet Pampa area in Argentina.
Rossby wave propagation regions are identified for two
basic states given by the composition of winters with
maximum and minimum frequency of GF occurrence,
during the 19611990 period. The stationary wavenumber
Ks indicates the regions where the Rossby wave propagation
is permitted and those where it will be inhibited
(Ks = 0), highlighting the importance of the jets as waveguides.
Nevertheless, differences exist between both basic
states analyzed. These differences indicate that the locations
for wave generation and its later evolution are conditioned
by the basic state. Results are validated through a
baroclinic model, which simulates the Rossby wave patterns
responsible for the teleconnection. Numerical experiments
confirm that the principal wave activity takes place
inside the subtropical and polar jets. In particular, for the
basic state with maximum frequency of GF occurrence, the
wave trains propagating inside the subtropical and polar
waveguides merge just before entering the continent, as
shown by the observations prior to the occurrence of GF
events. This configuration favors the development of an
intense south wind anomaly with large meridional extension
which results in the intensification of anticyclonic
circulation in southern South America. A conceptual model
is presented to summarise all these results.
Nevertheless, differences exist between both basic
states analyzed. These differences indicate that the locations
for wave generation and its later evolution are conditioned
by the basic state. Results are validated through a
baroclinic model, which simulates the Rossby wave patterns
responsible for the teleconnection. Numerical experiments
confirm that the principal wave activity takes place
inside the subtropical and polar jets. In particular, for the
basic state with maximum frequency of GF occurrence, the
wave trains propagating inside the subtropical and polar
waveguides merge just before entering the continent, as
shown by the observations prior to the occurrence of GF
events. This configuration favors the development of an
intense south wind anomaly with large meridional extension
which results in the intensification of anticyclonic
circulation in southern South America. A conceptual model
is presented to summarise all these results.
is permitted and those where it will be inhibited
(Ks = 0), highlighting the importance of the jets as waveguides.
Nevertheless, differences exist between both basic
states analyzed. These differences indicate that the locations
for wave generation and its later evolution are conditioned
by the basic state. Results are validated through a
baroclinic model, which simulates the Rossby wave patterns
responsible for the teleconnection. Numerical experiments
confirm that the principal wave activity takes place
inside the subtropical and polar jets. In particular, for the
basic state with maximum frequency of GF occurrence, the
wave trains propagating inside the subtropical and polar
waveguides merge just before entering the continent, as
shown by the observations prior to the occurrence of GF
events. This configuration favors the development of an
intense south wind anomaly with large meridional extension
which results in the intensification of anticyclonic
circulation in southern South America. A conceptual model
is presented to summarise all these results.
Nevertheless, differences exist between both basic
states analyzed. These differences indicate that the locations
for wave generation and its later evolution are conditioned
by the basic state. Results are validated through a
baroclinic model, which simulates the Rossby wave patterns
responsible for the teleconnection. Numerical experiments
confirm that the principal wave activity takes place
inside the subtropical and polar jets. In particular, for the
basic state with maximum frequency of GF occurrence, the
wave trains propagating inside the subtropical and polar
waveguides merge just before entering the continent, as
shown by the observations prior to the occurrence of GF
events. This configuration favors the development of an
intense south wind anomaly with large meridional extension
which results in the intensification of anticyclonic
circulation in southern South America. A conceptual model
is presented to summarise all these results.
s indicates the regions where the Rossby wave propagation
is permitted and those where it will be inhibited
(Ks = 0), highlighting the importance of the jets as waveguides.
Nevertheless, differences exist between both basic
states analyzed. These differences indicate that the locations
for wave generation and its later evolution are conditioned
by the basic state. Results are validated through a
baroclinic model, which simulates the Rossby wave patterns
responsible for the teleconnection. Numerical experiments
confirm that the principal wave activity takes place
inside the subtropical and polar jets. In particular, for the
basic state with maximum frequency of GF occurrence, the
wave trains propagating inside the subtropical and polar
waveguides merge just before entering the continent, as
shown by the observations prior to the occurrence of GF
events. This configuration favors the development of an
intense south wind anomaly with large meridional extension
which results in the intensification of anticyclonic
circulation in southern South America. A conceptual model
is presented to summarise all these results.
Nevertheless, differences exist between both basic
states analyzed. These differences indicate that the locations
for wave generation and its later evolution are conditioned
by the basic state. Results are validated through a
baroclinic model, which simulates the Rossby wave patterns
responsible for the teleconnection. Numerical experiments
confirm that the principal wave activity takes place
inside the subtropical and polar jets. In particular, for the
basic state with maximum frequency of GF occurrence, the
wave trains propagating inside the subtropical and polar
waveguides merge just before entering the continent, as
shown by the observations prior to the occurrence of GF
events. This configuration favors the development of an
intense south wind anomaly with large meridional extension
which results in the intensification of anticyclonic
circulation in southern South America. A conceptual model
is presented to summarise all these results.
Ks = 0), highlighting the importance of the jets as waveguides.
Nevertheless, differences exist between both basic
states analyzed. These differences indicate that the locations
for wave generation and its later evolution are conditioned
by the basic state. Results are validated through a
baroclinic model, which simulates the Rossby wave patterns
responsible for the teleconnection. Numerical experiments
confirm that the principal wave activity takes place
inside the subtropical and polar jets. In particular, for the
basic state with maximum frequency of GF occurrence, the
wave trains propagating inside the subtropical and polar
waveguides merge just before entering the continent, as
shown by the observations prior to the occurrence of GF
events. This configuration favors the development of an
intense south wind anomaly with large meridional extension
which results in the intensification of anticyclonic
circulation in southern South America. A conceptual model
is presented to summarise all these results.