Vorticity maps for various cases (see text), all based on the same original Gaussian field (displayed in panel a). The panels show the following: (a) initial conditions; (b–d) divorticity syntheses with (b) first order deformation, (c) advection then deformation, and (d) deformation only; (e) reference simulation at t = 2 (about 1/3rd turnover timescale); (f) basic synthesis for vorticity; (g, h) divorticity syntheses with (g) deformation then advection and (h) advection only. All syntheses are shown at the same time, t, as for the simulation and a coherence time based on the local strain time (See Section 2.4.2).