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Numerical Modeling and Forecasting of the Dust over Tehran Utilizing WRF-Chem Model

Seifi, Mohammad Mahdi | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51479 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Afshin, Hossein; Firoozabadi, Bahar
  7. Abstract:
  8. In recent years, the increase of particulate matter concentration due to frequent dust storms has become one of the most important dilemmas of people around the world. The high concentration of dust particles causes irreparable respiratory diseases, premature death, economic and social damages. Because of placement in the vicinity of the main sources of dust, Iran has been severely affected by the phenomenon of dust storms and damage caused by it.In this research, two dust storms occurred in Tehran are simulated using WRF-Chem and HYSPLIT models. The first event took place on February 2, 2016, and the second event took place on May 22, 2018. In order to determine the empirical parameters of the WRF-Chem model, the HYSPLIT model was initially simulated by the backward trajectory. The results of this simulation are used as inputs of the WRF-Chem model to forecast the emission, transfer, and computation of dust concentrations. Comparison of numerical modeling results with the observation of air quality measurement stations and satellite imagery shows the accurate dust concentration predicted by the model. In order to evaluate the numerical modeling results, an experimental relation between the visibility and the concentration of PM10 has been proposed. In the first case, the concentration of dust particles in Tehran exceeds 400 µg/m3. Furthermore, in order to determine the sources of dust in two recent events, the contour of dust emissions, a wind rose diagram of the main source of dust, the variation of spatial and temporal concentration of PM10 contour, and synoptic analysis of the atmospheric circulations and air fronts have been used. According to the above mentioned, the primary source of the two investigated dust storms is the arid region of Iraq in western Iran. Dust emissions in the eastern region of the Tigris River reach more than 20000 μg/m2s. Finally, the effect of the presence of dust particles on atmospheric dynamics and physical parameters has been analyzed. In this study, it has been shown that the presence of dust particles reduces the temperature of the earth's surface, increases the temperature of the middle layers of the atmosphere, increases the cloud cover, reduces wind speed, and reduces the planetary boundary layer. An increase in cloud cover is due to the presence of dust particles, contrary to previous research
  9. Keywords:
  10. Computational Fluid Dynamics (CFD) ; Numerical Modeling ; Dust ; Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT)Model ; Weather Research and Forecasting (WRF)Modeling System ; Field of View (FOV) ; Satellite Observations

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