A PARAMETERIZATION OF DIFFUSION INTO THE MIXED LAYER.

Abstract

THE DIFFUSION FROM A SOURCE NEAR THE GROUND INTO THE DAYTIME MIXED LAYER HAS BEEN DEDUCED FROM LABORATORY MEASUREMENTS, MAKING USE OF BOUNDARY-LAYER FREE CONVECTION SIMILARITY SCALING.A PARAMETERIZATION IS PRESENTED WHICH PRESERVES THIS SIMILARITY SCALING FOR INTERMEDIATE AND LONG-RANGE DIFFUSION, AND WHICH FOR SHORT-RANGE DIFFUSION INCORPORATES THE EFFECTS OF SOURCE HEIGHT AND OF NEAR-GROUND MECHANICALLY INDUCED MIXING.THE PARAMTERIZATION CAN BE APPLIED IN STEADY CONDITIONS TO THE POLLUTION CONCENTRATION DOWNWIND OF A STEADY SOURCE, OR IN UNSTEADY CONDITIONS TO THE CONCENTRATION IN AN EXPANDING CYLINDRICAL COLUMN ADVECTED WITHIN A MULTIPLE PUFF MODEL.THE PARAMETERIZATION APPLIES ONLY TO CHEMICALLY INERT, NONBUOYANT POLLUTANTS HAVING NO INTERACTION WITH THE GROUND.(A.)