ON THE PDF MODELS FOR ATMOSPHERIC DIFFUSION IN BOUNDARY LAYER^*

In this paper,taking its turbulent exchange coefficient as a function of the Lagrangian time scale and standard variance of the turbulence in atmosphere,the atmospheric dispersion PDF models are obtained on the basis of atmospheric diffusion K-theory.In the model the statistics of wind speed are directly used as its parameters instead of classic dispersion parameters.The bi-Gaussian PDF is derived in convective boundary layer (CBL),from the statistics of vertical velocity in both of the downdraft and updraft regions that are investigated theoretically in the other part of this paper.Giving the driven parameters of the CBL (including the convective velocity scale ω* and the mixing depth hi) and the time-averaged wind speed at release level,the PDF model is able to simulate the distribution of concentration released at any levels in the CBL.The PDF's simulations are fairly consistent with the measurements in CONDORS experiment or the results brought out by some numerical simulations.