MODELING THE DISPERSION OF ATMOSPHERIC POLLUTION USING CUBIC-SPLINES AND CHAPEAU FUNCTIONS

A quasi-Lagrangian cubic-spline and chapeau-function (Galerkin) methods are investigated and numerical results are compared in advecting a passive scalar. The methods are simple to use, are computationally fast, and give reasonably accurate results. Little numerical dissipation is manifested by the schemes. In simple advection tests with equal mesh spacing, chapeau functions maintain slightly more accurate peak values than the cubic spline method. In tests with unequal mesh spacing, the cubic spline method has less noise, but slightly more damping than the standard chapeau method. However, undesired noise can be reduced without significant distortion of the true concentration field by filtering or selective dissipation terms imbedded within the chapeau scheme. Both cubic splines and chapeau functions can be used to solve the dispersion of gaseous emissions in three dimension without excessive programming complexity or storage requirements. © 1979.