APES 7.3 Thermal Inversion
Enduring Understanding:
- Human activities have physical, chemical, and biological consequences for the atmosphere.
Learning Objective:
- Describe thermal inversion and its relationship with pollution.
Essential Knowledge:
- During a thermal inversion, the normal temperature gradient in the atmosphere is altered as the air temperature at the Earth’s surface is cooler than the air at higher altitudes.
- Thermal inversion traps pollution close to the ground, especially smog and particulates.
Thermal Inversion
- Under normal conditions in the troposphere, temperature decreases as altitude increases
- During thermal inversion, there is a reversal in the trend
- A warmer layer on top of the cooler surface air develops
- This is the opposite of the expected conditions
- Thermal inversion ‘traps’ cooler, denser air
- Air cannot rise, so pollutants do not disperse
- This includes photochemical smog and particulate matter
- Geography can encourage inversion layers
- Valleys, near mountain ranges, and coastal or prevailing winds increase the frequency of inversion layers
- Pollution is intensified by the inversion
- Large cities with high industrialization and many vehicles will be more affected by inversion