Richardson's extrapolation without interpolation in problems of advective-diffusive transport

It is offered to use Richardson's extrapolation on the basis of the up-wind scheme. Four difference problems with double grid steps at each grid point are solved simultaneously in one iteration process, which allows one to obtain a difference solution with the double grid step for all the grid points. The effect of this approach is illustrated on examples of solution of the two problems: of advection and of advective-diffusive transport.