Application and numerical experiments with a highly-accurate advection scheme in a regional transfer model

Summary

This paper examines a 19-level regional transfer model, EM3. The sensitivity of the results to different transfer schemes and effectiveness of using a high-precision scheme in raising modeling accuracy is examined. The use of a good scheme to improve the ability to simulate horizontal diffusion close to reality is also explored. EM3 was run with different precision schemes, i.e., a high-precision second-order moment conservation prather scheme (SOM for short) and an anti-diffusion Smolarkiewicz scheme (Smolar for short). The model was run 70 hrs. Results indicate that EM3 is much more sensitive to the precision of the schemes. SOM and Smolar, were compared, the former showing very weak numerical diffusion and computational dispersion so that positive solutions were kept. It is shown that i) numerical diffusion in SOM is one order of magnitude less compared to the latter; ii) the central intensity of transferred SO₂ increases by 4–5 times and the average motion trajectory of the concentration center is much improved in SOM; iii) SOM allows EM3 to precisely reflect the real horizontal diffusion. Therefore, choice of a high-precision advection scheme for EM3 will contribute greatly to an increase in its simulation accuracy.