A PDF Dispersion Model for Buoyant Plumes in the Convective Boundary Layer

Abstract A probability density function (PDF) dispersion model is presented for buoyant plumes in the convective boundary layer (CBL), where the mean concentration field C is obtained from the PDFs py and pz of tracer particle position in the lateral y and vertical z directions. The py is assumed to be Gaussian, whereas the pz is derived from the the vertical velocity PDF, which is skewed. Three primary sources contribute to the modeled C field: 1) the “direct” or real source at the stack, 2) an “indirect” source to account for the slow downward dispersion of lofting plumes from the CBL top, and 3) a “penetrated” source to treat material that initially penetrates the elevated inversion but later fumigates into the CBL. Image sources are included to satisfy the zero-flux conditions at the ground and the CBL top. Comparisons between the modeled crosswind-integrated concentration fields Cy and convection tank data show fair to good agreement in the lower half of the CBL. In particular, the Cy profiles at the...

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