Estimating Temporal and Seasonal Variation of Ventilation Coefficients



The main objective of a research program, whose output is presented here, has been to estimate “Ventilation Coefficients”, a critical parameter in determining air pollution concentration near the surface ground which signifies the ability for natural ventilation of an air shed in an urban or rural area. Relevant measured data from the city of Tehran has been used to calibrate and further demonstrate the validity of the mathematical model developed. Since most polluted mega cities require significant air pollution modeling activities, capable of providing relatively reliable outputs, calculating such highly important parameter is by far the most important outcome of this research. The Ventilation Coefficients have been estimated assuming normal adiabatic lapse rates and utilizing ten-year daily atmospheric radio-sound data. Mean Maximum Mixing Depth, Wind Speed at Mean Maximum Mixing Depth, and the Ventilation Coefficients have been computed and as a result it has been noted that despite the fact that Mean Maximum Mixing Depth peacks in June and Wind Speed at Mean Maximum Mixing Depth reaches its maximum in April, this has caused the Ventilation Coefficient to remain at its peack almost constant over April-June time span. It may also be observed for an urban area such as Tehran, the Ventilation Coefficient stands maximum in spring at 22329.17 m2/s and minimum in fall at 22329.17 m2/s.