Abstract
Lateral eddy diffusion coefficient in the horizontal planes of scalar quantities Ky was investigated by smallscale diffusion experiments and turbulent measurements in the atmosphere. In order to obtain the lateral eddy diffusion coefficient Ky, a Lagrangian spectral function in the inertial subrange was determined based on the experimental results, then Ky was calculated by means of this function.
In stable conditions, the results indicated that the values of the lateral eddy diffusion coefficient, Ky normalized by the vertical eddy diffusion coefficient Kz in neutral conditions was found to be about 10, and the ratio was almost uniform with the stability ζ(≡z/L: L being the Monin-Obukhov length). On the other hand, Kz decreases rapidly with increasing stability in stable conditions due to the buoyancy effects. Therefore, Ky/Kz increases rapidly with increasing stability. When the ratio of Ky/Kz in stable conditions was normalized to that in neutral conditions, its stability dependence was similar to the results of laboratory experiments by Ueda et al.
