Published online by Cambridge University Press: 18 February 2015
We study the scaling properties and Kraichnan–Leith–Batchelor (KLB) theory of forced inverse cascades in generalized two-dimensional (2D) fluids (  ${\it\alpha}$ -turbulence models) simulated at resolution
 ${\it\alpha}$ -turbulence models) simulated at resolution   $8192^{2}$ . We consider
 $8192^{2}$ . We consider   ${\it\alpha}=1$  (surface quasigeostrophic flow),
 ${\it\alpha}=1$  (surface quasigeostrophic flow),   ${\it\alpha}=2$  (2D Euler flow) and
 ${\it\alpha}=2$  (2D Euler flow) and   ${\it\alpha}=3$ . The forcing scale is well resolved, a direct cascade is present and there is no large-scale dissipation. Coherent vortices spanning a range of sizes, most larger than the forcing scale, are present for both
 ${\it\alpha}=3$ . The forcing scale is well resolved, a direct cascade is present and there is no large-scale dissipation. Coherent vortices spanning a range of sizes, most larger than the forcing scale, are present for both   ${\it\alpha}=1$  and
 ${\it\alpha}=1$  and   ${\it\alpha}=2$ . The active scalar field for
 ${\it\alpha}=2$ . The active scalar field for   ${\it\alpha}=3$  contains comparatively few and small vortices. The energy spectral slopes in the inverse cascade are steeper than the KLB prediction
 ${\it\alpha}=3$  contains comparatively few and small vortices. The energy spectral slopes in the inverse cascade are steeper than the KLB prediction   $-(7-{\it\alpha})/3$  in all three systems. Since we stop the simulations well before the cascades have reached the domain scale, vortex formation and spectral steepening are not due to condensation effects; nor are they caused by large-scale dissipation, which is absent. One- and two-point p.d.f.s, hyperflatness factors and structure functions indicate that the inverse cascades are intermittent and non-Gaussian over much of the inertial range for
 $-(7-{\it\alpha})/3$  in all three systems. Since we stop the simulations well before the cascades have reached the domain scale, vortex formation and spectral steepening are not due to condensation effects; nor are they caused by large-scale dissipation, which is absent. One- and two-point p.d.f.s, hyperflatness factors and structure functions indicate that the inverse cascades are intermittent and non-Gaussian over much of the inertial range for   ${\it\alpha}=1$  and
 ${\it\alpha}=1$  and   ${\it\alpha}=2$ , while the
 ${\it\alpha}=2$ , while the   ${\it\alpha}=3$  inverse cascade is much closer to Gaussian and non-intermittent. For
 ${\it\alpha}=3$  inverse cascade is much closer to Gaussian and non-intermittent. For   ${\it\alpha}=3$  the steep spectrum is close to that associated with enstrophy equipartition. Continuous wavelet analysis shows approximate KLB scaling
 ${\it\alpha}=3$  the steep spectrum is close to that associated with enstrophy equipartition. Continuous wavelet analysis shows approximate KLB scaling   $\mathscr{E}(k)\propto k^{-2}~({\it\alpha}=1)$  and
 $\mathscr{E}(k)\propto k^{-2}~({\it\alpha}=1)$  and   $\mathscr{E}(k)\propto k^{-5/3}~({\it\alpha}=2)$  in the interstitial regions between the coherent vortices. Our results demonstrate that coherent vortex formation (
 $\mathscr{E}(k)\propto k^{-5/3}~({\it\alpha}=2)$  in the interstitial regions between the coherent vortices. Our results demonstrate that coherent vortex formation (  ${\it\alpha}=1$  and
 ${\it\alpha}=1$  and   ${\it\alpha}=2$ ) and non-realizability (
 ${\it\alpha}=2$ ) and non-realizability (  ${\it\alpha}=3$ ) cause 2D inverse cascades to deviate from the KLB predictions, but that the flow between the vortices exhibits KLB scaling and non-intermittent statistics for
 ${\it\alpha}=3$ ) cause 2D inverse cascades to deviate from the KLB predictions, but that the flow between the vortices exhibits KLB scaling and non-intermittent statistics for   ${\it\alpha}=1$  and
 ${\it\alpha}=1$  and   ${\it\alpha}=2$ .
 ${\it\alpha}=2$ .