  We introduce a class of stochastic advection problems amenable to analysis of
turbulent transport. The statistics of the flow field are represented as a
continuous time Markov process, a choice that captures the intuitive notion of
turbulence as moving from one coherent structure to another. We obtain closed
form expressions for the turbulent transport operator without invoking
approximations. We recover the classical estimate of turbulent transport as a
diffusivity tensor, the components of which are the integrated auto-correlation
of the velocity field, in the limit that the operator becomes local in space
and time.
