Parameterisation of turbulence in the free atmosphere is an underdeveloped aspect of long-range transport and dispersion models, especially for off-line model where parameters such as the turbulent diffusion coefficient or the turbulent kinetic energy calculated by the meteorological model are not available. We are working on a parameterisation for CAT using the turbulence index described by Ellrod and Knapp (1991) in an aviation meteorology context. This index considers only dynamical aspects of the airflow. It is calculated as the product of the vertical wind shear and the horizontal deformation. We show examples of the sensitivity of this index to the grid resolution of the wind fields using horizontal maps and vertical cross-sections from the boundary layer into the stratosphere. For the stratosphere, a modification of the index may be necessary. All examples are based on ECMWF analyses. The effect of this parameterisation on long-range transport simulations with the Lagragian particle dispersion model FLEXPART will be demonstrated.