Estimating Temporal and Seasonal Variation of Ventilation Coefficients

Abstract

The main objective of a research program, whose output is presented\nhere, has been to estimate "Ventilation Coefficients", a critical\nparameter in determining air pollution concentration near the surface\nground which signifies the ability for natural ventilation of an air\nshed in an urban or rural area. Relevant measured data from the city of\nTehran has been used to calibrate and further demonstrate the validity\nof the mathematical model developed. Since most polluted mega cities\nrequire significant air pollution modeling activities, capable of\nproviding relatively reliable outputs, calculating such highly\nimportant parameter is by far the most important outcome of this\nresearch. The Ventilation Coefficients have been estimated assuming\nnormal adiabatic lapse rates and utilizing ten-year daily atmospheric\nradio-sound data. Mean Maximum Mixing Depth, Wind Speed at Mean Maximum\nMixing Depth, and the Ventilation Coefficients have been computed and\nas a result it has been noted that despite the fact that Mean Maximum\nMixing Depth peacks in June and Wind Speed at Mean Maximum Mixing Depth\nreaches its maximum in April, this has caused the Ventilation\nCoefficient to remain at its peack almost constant over April-June time\nspan. It may also be observed for an urban area such as Tehran, the\nVentilation Coefficient stands maximum in spring at 22329.17 m2/s and\nminimum in fall at 22329.17 m2/s.