(a) Parabolic Behavior

$/gamma(/vert {/boma h}/vert )/simeq{c/vert/boma{h}/vert}^2$ when $/boma{h}/rightarrow /boma{0}.$ $/gamma({/boma h})$ is twice differentiable at the origin and the random function is itself differentiable in the mean square sense. This type of behavior is characteristic of a highly regular spatial variability.