Theory of tracer distribution near the ground

Abstract

The peculiarities of tracer distribution in ground-layer air are investigated on the basis of the solution of the differential equation of turbulent diffusion. The use of numerical methods of solution and an electronic computer allowed us to calculate the concentration field from elevated sources under natural conditions of changes of horizontal and vertical wind velocity components and exchange coefficients. The use of both light and heavy pollutants as tracers is considered. Possibilities of using tracers under anomalous meteorological conditions when increased concentrations (elevated inversions, calms, etc.) can be created in the ground-layer air are also examined. The relationship between pollutant concentration from the source both in the presence and in the absence of wind is analyzed. The velocity field of air currents over rough terrain is studied theoretically by integration of the equation of motion. Air currents over some kinds of relief (hills and hollows) are investigated. For these problems, turbulent exchange is taken into consideration and potential currents near various forms of underlying surface are used for more schematic calculations. The field of vertical and horizontal velocity and turbulence is also determined on models with the help of wind-tunnel experiments. Characteristic forms of cross terrain and city buildings of old and new types are modeled.