7.3 Thermal Inversion

Vocabulary

• Thermal Inversion
• Inversion Layer

Description

Thermal inversion is a meteorological phenomenon that occurs when a layer of warm air becomes trapped above a layer of cooler air, creating a temperature reversal in the usual atmospheric temperature gradient. In a typical situation, the air temperature decreases with increasing altitude, a phenomenon known as the normal temperature lapse rate. However, during a thermal inversion, the air temperature increases with increasing altitude. This can occur at any altitude, but is most common in the lower atmosphere, near the earth's surface.

Thermal inversions are caused by a variety of factors, including the movement of cold and warm air masses, the presence of high pressure systems, and the presence of topographic features that can trap the warmer air. They can occur at any time of year, but are more common during the winter months when the earth's surface cools more quickly than the air above it.

Thermal inversions can have a number of impacts on the earth's climate and weather patterns. They can trap pollutants near the surface, leading to poor air quality and reduced visibility. They can also prevent clouds from forming, leading to clear skies and increased solar radiation. In some cases, thermal inversions can lead to the formation of frost or hoarfrost on the ground, as the warmer air above prevents the ground from cooling.

Thermal inversions can have a number of impacts on human health and well-being. They can increase the risk of respiratory problems, as the trapped pollutants can irritate the respiratory system. They can also affect the way that people feel, as the warm air trapped near the surface can lead to a feeling of stuffiness and discomfort.

Formation

Most cities sit on an open plain. Winds blow through them. The heat from the sun causes hot air to rise. Pollution is, therefore, able to move out of the city. 

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Some cities sit within a valley, surrounded by hills or mountains. This impedes the winds that normally blow through. The sun continues to heat the surfaces in the city and the warm air rises. At night, the warm air creates a thermal blanket that traps air pollution. 

Pollution

One of the most significant impacts of thermal inversion is its ability to trap pollutants near the earth's surface.

Normally, the air temperature decreases with increasing altitude, which causes pollutants to rise and disperse into the atmosphere. However, during a thermal inversion, the warmer air above acts as a "lid" that traps the pollutants near the surface. This can lead to a buildup of pollutants in the air, resulting in poor air quality and reduced visibility.

One of the main sources of pollutants that can be trapped by thermal inversion is car exhaust fumes. The emissions from cars contain a range of harmful chemicals, including carbon monoxide, nitrogen oxides, and volatile organic compounds. These pollutants are released into the air when a car burns fuel, and can contribute to the formation of ground-level ozone, a key component of smog.

Thermal inversion can also trap other types of pollutants, such as smoke from wildfires, industrial emissions, and particulate matter from construction sites. These pollutants can have a range of negative impacts on human health, including respiratory problems, allergies, and heart disease.

In addition to its impacts on air quality, thermal inversion can also affect the weather. The trapped warm air can prevent clouds from forming, leading to clear skies and increased solar radiation. In some cases, it can lead to the formation of frost or hoarfrost on the ground, as the warmer air above prevents the ground from cooling.

Overall, the relationship between thermal inversion and pollution trapping is complex and multifaceted. Thermal inversion can trap pollutants near the earth's surface, leading to poor air quality and reduced visibility. It can also affect the weather and have a range of negative impacts on human health. Understanding and predicting these inversions can help people to better prepare for and mitigate their impacts.

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🎥 Watch: AP Environmental Science - Air Pollution