Mark Petersen, November 7, 2003

These images show the time evolution of vorticity within a periodic box. Blue to green shows positive vorticity while red to orange shows negative vorticity. The governing equation is the Quasi-Geostrophic equation, an asymptotic derivation of the Navier-Stokes equations that models atmospheric and oceanic flows.

In these images gravity points downward. The images on the left are from a standard QG run, where rotation is vertical (like at the north pole). The images on the right are from an Intermediate QG run, where rotation is at a slanted angle (like at midlatitudes).

The first images show the initial condition, where a specified energy spectrum concentrates vortices at small scales. Same sign vortices on the same plane merge, so that many small vortices collect into a few large vortices. These vortices on each level align with same sign vortices above and below, so that at the end of the simulation a few large vortex columns dominate the flow. In the slanted rotation case on the right, the columns line up with the rotation vector.

Standard QG, time=0	Slanted QG, time=0
Standard QG, time=25	Slanted QG, time=25
Standard QG, time=50	Slanted QG, time=50
Standard QG, time=75	Slanted QG, time=75
Standard QG, time=100	Slanted QG, time=100