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