Study of the Vertical Dispersion Coefficient of Air Pollution Under Different Atmospheric Stability Conditions over Baghdad

The city of Baghdad is facing a real crisis of increasing air pollution due to increasing population density and industrial areas. This study aims to construct the specialized six curves for calculating vertical dispersion coefficients at different stabilities and distances from the measurement point, which can be represented by the urban atmosphere of Baghdad. This was also achieved in conjunction with the integrated Lagrangian time scale (T_L). The observed data were obtained through a three-dimensional ultrasonic anemometer for instantaneous velocity components and air temperature, as the study was from January to July of the year (2016). The vertical wind speed and the height dispersion coefficient were also calculated in the context of Lagrangian coordinates and related to the dimensionless atmospheric stability. The results show that T_L has the unity value at neutral, behaves in the linear increase at stable, and is non-linear under unstable conditions. Most of the stability is found in the slightly unstable segment range (–0.1 to –1) and it was found that the vertical dispersion coefficient plays an important role in measuring the dispersion of pollutants causing instability in the atmosphere. The dispersion coefficient is mainly produced by atmospheric turbulence, which is of great importance in mixing pollutants and spreading them horizontally or vertically.