Nonlinear Processes in Geophysics www.nonlin-processes-geophys.net 1023-5809 1607-7946 2 2 1995 10.5194/npg-2-89-1995 http://www.nonlin-processes-geophys.net/2/89/1995/ http://www.nonlin-processes-geophys.net/2/89/1995/npg-2-89-1995.html http://www.nonlin-processes-geophys.net/2/89/1995/npg-2-89-1995.pdf 89 100 0000-00-00 Flux-gradient relationship for turbulent dispersion over complex terrain F. Tampieri U. Giostra F. Trombetti D. Anfossi E. Ferrero G. Tinarelli Istituto FISBAT/CNR, Via Gobetti 101, 40129 Bologna, Italy Istituto ISIATA/CNR, Strada per Arnesano, 73100 Lecce, Italy Istituto ICG/CNR, corso Fiume 4, 10133 Torino, Italy Dip. Scienze e tec. Avanz., Universitá di Alessandria, Corso Borsalino 54, 15100 Alessandria, Italy ENEL/CRAM, Servizio Ambiente, Via Rubattino 54, 20134 Milano, Italy The transfer of a passive tracer in inhomogeneous turbulent flow is investigated. Starting from Lumley's constitutive equation, we derived an expression for the ratio between the effective eddy diffusivity <i>K</i> and eddy diffusivity <i>K</i> as a function of three length scales characterizing the local turbulence structure, flux variations and turbulence inhomogeneities. The theoretical predictions for the one-dimensional case of inhomogeneous symmetric turbulence were validated through a comparison with the numerical results of a Lagrangian particle model simulating a wind tunnel experiment of dispersion in the lee of an idealized two-dimensional hill. A qualitative agreement is reached between the theoretical evaluation of <i>K</i> and the value obtained from the numerical simulation.