| With the development of social economy,fog-haze has gradually become the main problem of environmental pollution in China,and the air pollution problem in Guanzhon g area centered on Xi'an is becoming more and more serious.At the same time,the air pollution problem is also a regional environmental pollution problem.Under certain influences of weather conditions and geographical location,there will be pollutant transport in the adjacent areas.Fog-haze aerosols are affected by local pollutant emissions and cross-region al transport,which are two important sources of air pollution and a hot research topic of fog-haze aerosols.As a very effective research method,numerical simulation has been paid more and more attention and development.Therefore,it is necessary to analyze the distribution and transport characteristics of fog-haze aerosol in Xi'an area comprehensively.In this thesis,the WRF-Chem model is used to simulate the fog-haze in Xi'an.A fog-haze case in Xi'an where is one of the key areas of air pollution in China,is selected to simulate the whole process of the fog-haze by adjusting the model simulation scheme.The qualitative,quantitative evaluation and comprehensive comparison of the simulated data are carried out respectively,and the results show that the WRF-Chem model has successfully reproduced the fog-haze process,and the simulation data can be used in the study of aerosol characteristics.Using simulation data and observation data from ground monitoring stations to analyze the distribution and transportation characteristics of the fog-haze,it can be seen that each component of the fog-haze aerosol decreases with the increase of height,the highest vertical distribution is about 5km,and the highest concentration is near the ground.During the fog-haze dissipation period,the pollutants existed in Tongchuan-xi'an-shanyang transportation path.Considering that the research of the fog-haze should also analyze the overall three-dimensional distribution structure and four-dimensional spatial-temporal evolution,the visualization method of model output data is designed.The visualization method includes three-dimensional visualization of PM2.5 mass concentration,HGT terrain height data,and wind field data to analyze the influence of wind field on the fog-haze transportation.The visualization method is verified by the analysis of the fog-haze case.Compared with the analysis in Chapter 3,the visualization method shows that the fog-haze formation period belongs to the regional accumulation type.In the dissipation period,the fog-haze at the bottom layer dissipates first,while the fog-haze at the upper layer changes little,and there is still a fog-haze layer at the upper layer when the ground fog-haze has dissipated.Through the comprehensive analysis of the fog-haze case and the verification of visualization method,the results show that:(1)The research scheme of the fog-haze distribution and transportation characteristics in Xi'an is feasible.The research scheme includes the air mass trajectory tracking method,WRF-Chem model simulation method,model data visualization method and radar data processing method.Other later analysis can apply this scheme to obtain the corresponding distribution and transportation characteristics of fog-haze aerosol.(2)Through the debugging and selection of the WRF-Chem mode physical scheme and chemical scheme,a simulation scheme suitable for the fog-haze analysis in Xi'an was obtained.(3)A visualization method suitable for the output data format of the model is designed.This method can supplement the existing analysis methods.(4)Obtained the distribution and transportation characteristics of a type of fog-haze aerosol in Xi'an,which can provide some reference for the early governance of the fog-haze and the construction of Urban Ventilation corridor by the government. |
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