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Investigation of the Influence of Meteorology-Chemistry Interaction on the Results of Air Quality Modeling During a Highly Polluted Episode in Tehran

Sadeghi Maleki, Ensiyeh | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53424 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Firoozabadi, Bahar; Hosseini, Vahid
  7. Abstract:
  8. Atmospheric aerosols scatter or absorb a fraction of the incoming solar radiation to cool or warm the atmosphere, decreasing surface temperature and altering atmospheric stability to further affect the dispersion of air pollutants in the planetary boundary layer. This study aims to evaluate the impacts of meteorology-chemistry interaction on the meteorology and air quality simulations over Tehran megacity. The Coupled Weather Research and Forecasting-Community Multiscale Air Quality (WRF-CMAQ) modeling system was applied to model a period of time from 3rd to 23rd December of 2017. Comprehensive model evaluations for meteorology demonstrated that the modeling system had the capacity to reproduce the observations, and could capture the temporal and spatial variations of radiation, temperature, and wind speed; Of course, there were larger differences between the simulation and observation in urban sites than non-urban sites. Comprehensive model evaluations for chemistry showed that there were differences between present calculations and observations; PM10 concentrations were much smaller than observations, but other pollutants were close to the observations in most of the sites. The aerosol direct effect on meteorology and air quality were calculated by taking the differences between the results of the online simulations and the offline ones. The aerosol direct effects moderately decreased the shortwave radiation, planetary boundary layer height, temperature and wind velocity by -7.0579 w/m2 (-4.9169 %), -16.1919 m (-6.0287 %), -0.1891 k (-0.0677 %), and -0.0265 m/s (-1.0113 %), respectively. Consequently, the meteorological response to direct effects led to changes in air pollutant concentrations. The comparison between Online and offline simulations showed the concentrations of O3, PM2.5, and PM10 decreased and the concentrations of CO, SO2, and NO2 increased. The concentrations of O3, PM2.5 and PM10 was found to decrease by -0.388 ppb (-1.6208 %), -0.8355 µg/m3 (-3.7361 %) and -7.5154 µg/m3 (-20/6119 %) and the concentrations of CO, SO2 and NO2 was found to increase by 0.0114 ppm (11.2647 %), 0.012 ppb (-7.8217 %), and 0.4953 (1.2575%) over the entire domain. A correlation matrix clarifies that the effect of aerosol on air pollutants concentrations. The increase or decrease in the O3 concentration depended on the responses of the atmospheric dynamics as well as the photolysis rates. This study demonstrated that the effect of meteorology-chemistry interaction on meteorological and chemical modeling results is negligible
  9. Keywords:
  10. Aerosols ; Weather Research Forecasting (WRF) ; Community Multiscale Air Quality Modeling System (CMAQ) ; Air Quality Modeling ; Tehran's Weather ; Offline Simulation ; Online Simulation ; Meteorology-Chemistry Interaction

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