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Australia: The Land Where Time Began |
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Rossby Waves Mediate Impacts on West Antarctic Atmospheric Circulation
of Tropical Oceans
Climate change around Antarctica has been found by recent studies to
link to the sea surface temperature of tropical oceans, with
teleconnections from the Pacific, Atlantic and Indian Oceans which make
different contributions to the climate of Antarctica. In this study Li
et al. have identified the
impacts of each ocean basin on the circulation of the Southern
Hemisphere in the austral winter by the use of simulation results from a
comprehensive atmospheric model, an idealised dynamical core model, and
a theoretical Rossby wave model. It is shown by the results of these
comparisons that warming in the tropical Atlantic Ocean, warming of the
Indian Ocean, and cooling of the eastern Pacific Ocean are all capable
of deepening the Amundsen Sea Low that is located adjacent to West
Antarctica, while warming of the western Pacific increases the pressure
to the west of the international date line, encompassing the Ross Sea as
well as regions to the south of the Tasman Sea. These tropical ocean
basins were found to work together linearly to modulate the circulation
of the atmosphere around West Antarctica in the austral winter. It was
indicated by further analysis that these teleconnections depend
critically on stationary Rossby wave dynamics and therefore are
sensitive to the background flow, in particular the
subtropical/midlatitude jet. Wind shear is amplified near these jets,
which strengthens the generation of Rossby waves. On the other hand, the
meridional gradient of the absolute vorticity near the edges of the jets
is also enhanced. The edge of the jet may reflect stationary Rossby wave
trains, thereby serving as a waveguide, as a consequence of the Rossby
wave dispersion relationship. As well as identifying the roles of each
of the tropical ocean basins in the tropical-Antarctic teleconnection,
the simulation results also suggest that a deeper understanding of
teleconnections requires a better estimation of the atmospheric jet
structures.
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |