Part IV: Giving a hoot : pollution and Environmental Quality
Although smog is not isolated to urban areas, it’s more common around cities. One factor that intensifies smog in urban areas is the occurrence of a thermal inversion in the atmosphere . Generally speaking, the temperature of the air becomes gradually cooler as you move upward in the atmosphere : warm air near the surface moves upward , gradually cooling . In the case of a temperature inversion however , atmospheric circulation and geographic factors trap a layer of warm air between two layers of cooler air,inverting or flipping the usual pattern. Figure 15-1 illustrates what this effect looks like.