Significant progress has been made toward the goal of developing a viable computer model based on second-order closure of the turbulent correlation equations for predicting the fate of nonchemically reacting contaminants released in the atmospheric boundary layer. The invariant turbulent model discussed in previous reports has been modified both by extending its capabilities and by developing approximations to the full system of equations which may be used in complicated flow geometries where economy of computing time justifies some compromise in accuracy. Sample calculations of several flow problems of current practical interest are included. These are: that of the diurnal variations in the turbulence distributions in the planetary boundary layer induced by the unsteady surface heat flux; the spatial variation of turbulence occurring when the wind blows over an abrupt change in surface roughness; and the dispersal of a plume released at different heights, under different stability conditions, and over different terrain.

"EPA project officer: Douglas G. Fox." "Prepared for Office of Research and Development, U.S. Environmental Protection Agency." "September 1974." "Contract No. 68-02-1310; Grant No. R-800662; ROAP No. 21ADO; Program Element No. 1AA009; " "EPA-650/4-74-035." PB 239 323--NTIS. Includes bibliographical references.