Mécanique et mathématiques numériques en sciences géologiques
Some simple models for tropical-extratropical interactions
Khouider, Boualem
University of Victoria

While the midlatitude weather and climate variability is associated with quasi-geostrophic planetary Rossby waves that are fairly easy to predict via simple dry dynamical models such the  quasi-geosptrophic equations, the atmospheric variability in the tropics involves a hierarchy of equatorially trapped  waves  that interact strongly with moist convection. Equatorially trapped waves display a wide variety of physical and dynamical features including geostrophic balance and non-balance, dispersive and non dispersive behaviour, symmetric and anti-symmetric structure. They propagate in both directions along the equator and are responsible for a significant portion of weather variability in the tropics on the scales of a few days to months. The  interactions between equatorially trapped and midlatitude  Rossby waves  play a major role in the lateral energy exchange between the tropics and extra-tropics. In fact, it is believed that progress in medium to long range weather forecasts, over a few weeks to months, and climate predictions in particular,  depends on a proper representation of tropical convection and associated rain fall variability in numerical weather prediction and global climate models. In this talk, I will use some simplified primitive equation models to illustrate some scenarios of tropical and extra-tropical interactions of equatorially trapped waves and barotropic Rossby waves, which propagate north- and southward from the tropics to the midlatitudes.

Mardi, 18 juin, 11h00
Salle Du Jardin