Inversion (meteorology) - Consequences of A Thermal Inversion

Consequences of A Thermal Inversion

Temperature inversion stops atmospheric convection (which is normally present) from happening in the affected area and can lead to the air becoming stiller and murky from the collection of dust and pollutants that are no longer able to be lifted from the surface. This can become a problem in cities where many pollutants exist. Inversion effects occur frequently in big cities such as:

• Los Angeles, California, United States
• Mexico City, Mexico
• Mumbai, India
• Santiago, Chile
• São Paulo, Brazil
• Tehran, Iran

but also in smaller cities like:

• Boise, Idaho, United States
• Brisbane, Queensland, Australia
• Chiang Mai, Thailand
• Launceston, Tasmania, Australia
• Ljubljana, Slovenia
• Logan, Utah, United States
• Oslo, Norway
• Prague, Czech Republic
• Salt Lake City, Utah, United States
• Vancouver, British Columbia, Canada

These cities are closely surrounded by hills and mountains that, together with the inversion effect, bottle-caps the air in the city. During a severe inversion, trapped air pollutants form a brownish haze that can cause respiratory problems. The Great Smog of 1952 (London, England), is one of the most serious examples of such an inversion; it was blamed for an estimated 11,000 to 12,000 deaths.

Sometimes the inversion layer is at a high enough altitude that cumulus clouds can condense but can only spread out under the inversion layer. This decreases the amount of sunlight reaching the ground and prevents new thermals from forming. As the clouds disperse, sunny weather replaces cloudiness in a cycle that can occur more than once a day.

As the temperature of air increases, the index of refraction of air decreases, a side effect of hotter air being less dense. Normally this results in distant objects being shortened vertically, an effect that is easy to see at sunset (where the sun is "squished" into an oval). In an inversion, the normal pattern is reversed, and distant objects are instead stretched out or appear to be above the horizon, leading to the phenomenon known as a Fata Morgana (or mirage).