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# Steady State Pollution Concentration from Box Model for City

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1) Consider an urban area (100 km^2) with a temperature profile that decreases linearly with height between 30 degrees C at the surface, and 24 degrees C at 500 m. At 500 m, the temperature increases with height to 30 degrees C at 1000 m.
What is the mixing height for this situation?
Using a box model for the city, calculate the average steady-state concentration of pollutants if the average pollutant emissions from the city are 2×10^-5 g m-2 s-1 and the wind speed is 4 m s-1.

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1) Consider an urban area (100 km2) with a temperature profile that decreases linearly with height between 30o C at the surface, and 24o C at 500 m. At 500 m, the temperature increases with height to 30o C at 1000 m.
What is the mixing height for this situation?

The increase in temperature after the linear decrease causes an "inversion layer". (http://www.engin.umich.edu/labs/EAST/me589/gallery/CCAQ_f04/mixing_height_inv.htm) explains it well....

"Mixing Height and Inversions
The mixing height is the height of vertical mixing of air and suspended particles above the ground. This height is determined by the observation of the atmospheric temperature profile. A parcel of air rising from the surface of the Earth will rise at a given rate (called the dry-adiabatic lapse rate). As long as the parcel of air is warmer than the ambient temperature, it will continue to rise. However, once it becomes colder than the ...

#### Solution Summary

This highly detailed solution shows how to calculate steady-state concentration of pollutants in a city using a box model for the city.

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