http://file3.status.net/i/identica/-20120307T213535-zv9gsgc.html

Fig. 1. Particles spacing on 20 March, 2011 at 12:00 UTC (top) and on 27 March, 2011 at 18:00 UTC (bottom); shades of red indicate particles in the bottom layer, up to 3 km; black to dark blue indicate the middle layer, up to 6 km height; and light blue indicates the upper layer; the trajectories were simulated using the Lagrangian dispersion model (time of the particles release was on 12 March 2011). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)