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Air Quality Part 11

Tham khảo tài liệu 'air quality part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Nonlocal-closure schemes for use in air quality and environmental models 243 Fig. 3. The eddy diffusion OLD versus TKE scheme. Comparison of the modeled and observed NO2 in air pg N m-3 concentrations left panels and their biases right panels in the period April-September for the years 1999 2001 and 2002. M and O denotes modeled and observed value respectively. The statistics gave the following values 1 TKE V 0.548 VBR 0.293 7 0.211 7 0.147 and OLD v 0.802 VBR 0.433 7 0.303 7 0.147 and 2 VUR v 0.571 pg N m-3 VBR 0.056 pg N m-3 7 0.219 pg N m-3 7 0.211 pg N m-3 and OLD v 0.802 VBR 0.159 7 0.303 7 0.211 . A comparison of 7 and 7 for 1 and 2 shows that difference between them is evidently smaller with the TKE and VUR scheme schemes versus the OLD one. 244 Air Quality Fig. 4. The eddy diffusion OLD versus the VUR scheme. Comparison of a the modelled and observed NO2 in air pg N m-3 concentrations and b their biases in the period April-September for the year 2002. M and O denotes modelled and observed value respectively. 4. Conclusions In the ABL during convective conditions when much of the vertical mixing is driven by buoyant plumes we cannot properly describe mixing processes using local approach and eddy diffusion schemes. Nonlocal-closure schemes simulate much better vertical mixing than local ones. In this chapter two nonlocal schemes the TKE scheme and the VUR scheme for applications in air quality and environmental models are described. The comparison of the TKE scheme and the VUR one with an eddy diffusion scheme OLD commonly used in chemical transport models was done. These comparisons were performed with the EMEP Unified chemical model using simulated and measured concentrations of the pollutant NO2 since it is one of the most affected ones by the processes in the ABL layer. Nonlocal shemes gave better results than local one. Acknowledgement The research work described here has been funded by the Serbian Ministry of Science and Technology under the project .