TESTING ADVECTION SCHEMES IN A 3-DIMENSIONAL AIR-POLLUTION MODEL

A three-dimensional air pollution model is in the process of development at the National Environmental Research Institute. The model will be used to study long-range transport from the industrial areas in Europe, Asia, and North America to the Arctic. It is important to choose good advection schemes for such a model. The advection process can be split into two parts: (i) horizontal advection and (ii) vertical advection. Different schemes can be used in the different parts. It will be shown that it is efficient to apply a pseudospectral algorithm in the horizontal layers, while the use of a Galerkin finite elements algorithm is more appropriate along the vertical grid-lines. It will be explained why such a combination is a good choice when big long-range transport air pollution models are to be treated numerically. A three-dimensional test-example was constructed and used in the experiments. The test-example describes a problem that is close to the real situation. Its analytical solution is known. Therefore, such an example can successfully be applied to check the performance of the advection part of the model. It is demonstrated that the advection schemes chosen perform well on this test-example.