Department of Geophysical Atmospheric and Planetary Sciences, Tel Aviv University,
Department of Meteorology (MISU), Stockholm University,
Thursday 26th of September 2013 – 10.00 am till 12.00am – Room Nano BM 6204
The concept of Counter-propagating Rossby Waves (CRWs) has been introduced by Bretherton (1966) to explain the basic mechanism of baroclinic instability in the atmosphere. This is the main mechanism which generates cyclones and hence determines the weather in the mid-latitudes. CRWs are vorticity waves which propagate in regions of strong vorticity gradients in a counter-direction to the mean flow (the mid-latitudinal atmospheric jet ). They interact in a distance by inducing a far velocity field which enables them to be phase-locked in a growing configuration.
In this talk I will try to relate this approach to general shear flow instability and to show how it rationalizes different fundamental aspects of the instability including the necessary conditions for the onset of the instability, and the mechanism of optimal non-normal growth and how it feeds back with nonlinear mixing.
Finally, I will suggest a more general type of modified Rossby-gravity wave instability in the presence of stratification, where the dynamics is formulated solely in terms of vorticity and wave displacement across the shear. I will argue that the latter formulation can be generally applied to various different setups where external forces generate vorticity by exerting torque on the flow.
Eyal Heifetz obtained Bachelors and Masters degree in Geophysics and Planetary Sciences from Tel-Aviv University. In 1998 he finished his Ph.D. also at Tel-Aviv University, whereafter he become a Post Doctorate Research Fellow at Harvard University. In 2001 he returned to Tel-Aviv University first as a lecturer and from 2004 as senior lecturer with tenure. Since 2010 he is an Associate Professor there. 2012-2013 he worked as a Rossby Visiting Fellow at the International Metrological Institute at Stockholm University.