High Gravity Wave Activity Observed in Patagonia, Southern America: Generation by a Cyclone Passage over Andes Mountain Range

PULIDO M.; M. M. LUCINI; C. RODAS; H. TEITELBAUM

Foz Iguazu (Brazil)

Conferencia; The Meeting of the Americas, American Geophysical Union; 2010

American Geophysical Union

The generation and propagation of gravity waves in Patagonia region (South of South America) in an event of strong wave activity from 30 Oct 95 to 1 Nov 95 is examined trough radiosondes measurements and WRF simulations. The analysis shows that the observed waves are generated by flow over the Andes mountain range. The strong surface wind found near the mountains is related to a cyclone that is propagating south-eastward in the South Pacific ocean and approaching the western coast of the continent. A rich horizontal wavenumber spectrum is generated due to the direction of surface wind changes rapidly during the cyclone passage. The waves propagate long zonal and meridional (lateral) distances due to the background conditions. They are found on 1 Nov 95 over Tierra del Fuego a fact that is corroborated with both WRF simulations and a ray tracing technique. The waves continue their propagation over the Passage Drake. The characteristics of the waves are strongly influenced by the strong background wind shear at the region during their propagation. The perturbation field possesses elliptical polarization at 14-21 km height range, this fact is shown to be due to orographic waves that are propagating toward their critical levels and so the polarization becomes more and more circular.