Tuesday, 24 January 2012: 12:00 PM

New Developments in Geostrophic Turbulence Since Wiin-Nielsen

Room 353 (New Orleans Convention Center )

One of the many areas in geophysical fluid dynamics that Aksel Wiin-Nielsen made contributions was the large scale turbulence of atmospheric flow. Aksel studied energy and enstrophy cascades and was one of the first to detect in the atmosphere the -3 power law predicted in two-dimensional turbulence theory put forward by Batchelor and Kraichnan in the late 1960s. A consequence of this observational finding is the fact that, unlike three-dimensional turbulence in which the eddy turnover time decreases with eddy length scale, in two dimensional and quasi-geostrophic turbulence the eddy turnover time is constant independent of eddy length scale in the enstrophy cascading range. A further consequence of this is that the Rossby number is constant through the enstrophy cascade. This implies that instabilities which depend on ageostrophic processes are restricted because the scaling laws which imply balanced, quasi-geostrophic dynamics are valid at all length scales. Recent results show, however, even given that all of the above statements are true and maintained in the dynamics, there is a mechanism through which quasi-geostrophic turbulence becomes inconsistent and develops the seeds of its own destruction at small scales.

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