What is Temperature Inversion? | The Different Types, Causes, & Effects
Have you ever seen smog linger over a city? Well, this is often caused by a Temperature Inversion, and it’s a deviation from your typical meteorological phenomenon.
The region of the atmosphere closest to Earth’s surface is called the troposphere. Generally, the air in the troposphere is warmer than the layers of air above it. The standard rule of meteorology is that air gets cooler with an increase in altitude.
But temperature inversions change that.
As a result, you’ll see weather phenomena like fog, smog, mist, and hazy horizons. Generally, it’s more common in mountainous regions or valleys or during winter when a cold night breeze from the mountains swoops to the ground.
But what are temperature inversions? Well, we’ll explain the different types, effects, and their relationship with air pollution here.
Temperature Inversion Definition
Temperature inversions occur when a layer of warm air traps cool air near the Earth’s surface. This is the inverse of what normally happens. Most of the time, for example, the Earth’s surface is warm during the day and air gets colder the higher you go.
A temperature inversion usually happens during the night when the ground temperature drops because it’s no longer heated by the sun.
4 Types of Temperature Inversions
There are 4 types temperature inversions to know about:
- Ground or Radiation Inversion. The temperature inverses when the air near the ground is cooled off more rapidly than the layer of air above it.
- Turbulence or Vertical Advection. Turbulence inversion happens when stagnant air lids turbulent air. The turbulent layer transports heat downwards, cooling its upper layer (vertical mixing). But the layer of static air is unmixed and thus so it’s warmer than below.
- Subsidence Inversion. When a significant layer of air descends due to high pressure, it warms up rapidly, and the air at lower altitudes remains colder.
- Frontal Inversion. When warm and cold air current meets, cold air raises the warm air due to differences in densities.
How Do Temperature Inversions Form?
Depending on the type of inversion, there are different causes. Factors like the weather and geography can all have an impact. Here’s a list explaining what causes different temperature inversions:
- Radiation inversions happen when the ground is heated due to radiations from the sun during the day and then cools off rapidly during the night. As a result, the air in contact with the ground also cools down. If air temperature falls below its dew point, fog forms. The topography of the region plays a significant role in this case.
- Vertical advection usually happens in valleys where air and sun’s radiations can travel vertically.
- Subsidence inversions are common in northern regions or subtropical oceans. They form due to high air pressures and anti-cyclones.
- Frontal inversions occur in temperate zones where warm western winds converge with the cold northern polar winds and give rise to anti-cyclonic conditions.
The Effects of Temperature Inversion
Temperature inversion is an important contributor to cloud formation, fog, smog, lack of precipitation, and visibility disruption. Here is how temperature inversions affect our environment:
- Visibility: Cooler air gets trapped within a layer of warmer air, and the moisture condenses and forms clouds called smog. But since these clouds cannot escape the level of inversion, they cause poor visibility in that region.
- Rainfall: Because the clouds cannot get high enough, there is no rain. This has adverse effects on the agriculture industry.
- Diurnal variations: Temperature inversion also affects the usual fluctuations in temperature throughout the day. Typically, the sun’s radiation heats the ground during the day. The heat energy transfers to the air above the ground through convection and conduction. Due to the accumulation of cool air in temperature-inverted areas, the heat transfer is minimal, and diurnal temperature variation is slight.
- Thunderstorms and tornados: Inversions also cause intense thunderstorms and tornadoes because of the energy trapped high up in the atmosphere.
- Pollution: Finally, smoke, dust, and pollutant particles get trapped in the troposphere, and they can react with each other to form chemicals that are hazardous when inhaled, like smog.
How Temperature Inversions Relate to Air Pollution
Air pollution and temperature inversion are a dangerous combination. In areas where the concentration of air pollutants is high, temperature inversions can significantly affect the our society’s health.
The envelope of hot air surrounds the cool air of a region and traps the pollutant particles in it. Because of the restricted airflow, these particles remain stagnant. Then, the particles react with each other to turn even more deadly, creating a lingering, harmful smog.
During winter, inverse temperatures are more common in the northern hemisphere. Add to that, air pollution is made worse due to houses burning wood or coal for warmth—further releasing harmful pollutants into the air.
So, what can you do about it?
One way is by monitoring the air around you.
Monitor the Particulate Matter levels around the world with our free, real-time PurpleAir Map or join PurpleAir's mission to make air quality data accessible to everyone by investing in an air quality monitor for your home.
Together, we can be informed and make changes in our daily habits and the community to improve air quality.