Page 340 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

318 11 Air Dispersion

11.2 General Gaussian Dispersion Model

While the box model is useful for certain applications, it cannot be used for predicting
the concentration in the atmosphere where air is subjected to mixing and concen-
tration changes with time and location. For this kind of problem, we have to use other
complex air dispersion models by considering the effect of meteorology. Before we
start the mathematical expression of the models, we first put forward a few concepts.

11.2.1 Atmosphere

The temperature and pressure of the Earth’s atmosphere change with elevation.
Based on the variation of the average temperature profile with altitude, atmosphere
can be divided into five distinguished layers (Fig. 11.3). From near Earth surface
upward to the space, they are called [21]
• Troposphere,
• Stratosphere,
• Mesosphere,
• Thermosphere,
• Exosphere.

Troposphere is the lowest layer of the atmosphere, which is below 8–18 km
altitude, depending on latitude and time of year, from the Earth’s surface; In this
region, temperature decreases with height, and there is a rapid vertical mixing of air.

Fig. 11.3 Schematic diagram of atmosphere layers and temperature profile (not in scale)