Spatially correlated and inhomogeneous random advection

We study the equilibrium statistics of an idealized model of random advection. Theoretical results for large-scale homogeneous forcing - notably the shapes of the PDFs - are recovered; they are compared with results for various inhomogeneous and intermittent forcings. The correlation times of the forcings are varied. The PDFs are interpreted in terms of the underlying mixing time scales. Conditional statistics of the tracer field - the conditional diffusion in particular - are computed; they are used to elucidate the influence of small-scale tracer-field correlations. We contrast results for spatially smooth and spatially rough velocity fields. © 2000 American Institute of Physics.