What Is Temperature Inversion And How Does it Affect The Weather?
Normally, the temperature continues to fall as altitude increases. It roughly drops by 9.8° Celsius every 1 000 meters (5.4° Fahrenheit every 1 000 feet). Most of us experienced this scientific occurrence at some point during our lives, when walking outside on a tall building or hiking up a mountain.
There is a phenomenon, however, that turns this norm on its head by causing an increase in temperature with height. It is called Temperature Inversion.
We take a closer look at what a temperature inversion is, what causes it, and its impact on the weather and environment.
What is Temperature Inversion?
A temperature inversion can be defined as a phenomenon through which a rise in temperature takes place as altitude increases in a layer of air. This is in contrast to the normal behavior of air throughout the atmosphere where temperature typically decreases as altitude increases.
This phenomenon can take place in a fixed position like the stratosphere, where the temperature naturally rises with height.
(The average temperature in the stratosphere starts at -51° Celsius (-60° Fahrenheit) above the troposphere, and rises to average of -15° Celsius (5° Fahrenheit) close to the mesosphere.)
Temperature inversion also takes place in pockets or layers of air throughout the atmosphere caused by different variables. These layers are not so easily predictable and can have a dramatic impact on the weather and environment.
Causes And Types Of Temperature Inversion
In this section, we will focus on the different variables that cause the inversion layers that appear randomly throughout the atmosphere. Temperature inversion is primarily caused by four different factors, resulting in four types of inversion:
1) Surface Inversion
This form of temperature inversion usually takes place on a cloudless night with little or no wind present, creating the perfect conditions for heat to escape rapidly from the surface.
As a result, the air at the surface cools down much more quickly than the air above it in the atmosphere, creating a low-lying temperature inversion.
2) Frontal Inversion
Colder air is more dense and heavier than warmer air, which means a cold front is also heavier and thicker than a warm front.
When the two fronts meet, the lighter and warmer air from the warm front is lifted up by the cold and dense air from the cold front, resulting in warm air on top of a layer of cold air.
Unlike the other forms of temperature inversions, a frontal inversion takes place much higher up the atmosphere, as the size and steep gradient of the cold front allow the warmer air to be raised up to higher altitudes.
To find out more about warm and cold fronts and their characteristics, you can read more about it in this article.
3) Subsidence Inversion
This form of temperature inversion is a direct result of the pressure caused by huge masses of air. When these large volumes of air start to descend, it compresses the air within the layer which leads to an increase in temperature.
It also has the added effect of slowing the speed at which temperature change takes place (lapse rate). If this layer of warm compressed air continues to descend, it causes the air higher up in the atmosphere to be warmer than the air closer to the surface.
The topography of the surface can also be responsible for the creation of a temperature inversion. A good example of this form of inversion is the one that takes place at night in the valley between hills or mountains.
When it cools down in the evening, the surface of the slopes on the hillside (or mountain peaks) cools down quicker than its surroundings, causing the air above it also to cool down. The colder air starts moving down the slopes and accumulates at the bottom of the valley.
As the colder air moves into the valley, it lifts the warmer air at the bottom up and away from the surface. This leaves the valley with colder air at the surface and warmer air higher up in the atmosphere.
The Effects Of Temperature Inversion
Due to the "unnatural" nature of temperature inversion, some unexpected and extreme conditions are created as a result of this phenomenon. Some of these results can be seen as potentially harmful and dangerous. The most important ones are:
1) Freezing Rain
Under normal conditions, when ice crystals combine to form snowflakes in subzero temperatures, it falls to the ground and stays intact as it falls through colder air as it nears the surface.
With an inversion layer present, though, the snow melts as it falls through the warmer air. When it exits the layer, it does not have enough time to freeze again, but the temperature in the raindrops continue to drop to below freezing point, creating supercooled water.
This is called freezing rain, and as soon as these cold raindrops hit the surface, they are immediately turned into ice. This is extremely dangerous, as the thin layer of ice that is formed, is almost invisible and extremely slippery.
When this ice forms on the surface of roads or pavements where people walk, it makes these surfaces very slippery almost impossible to spot. This is referred to as black ice and is a major cause of accidents on and off the road in countries frequently experiencing this weather phenomenon.
(You can get more in-depth information about freezing rain, supercooled water, and similar phenomena in this article.)
2) Sound Amplification
A temperature inversion also has the effect of amplifying sounds below it. It as act as giant reflective ceiling under which all sound generated is refracted down.
This means sounds can travel further and sound much louder than it really is. For example, it has been extensively reported that thunderstorms sounds much louder when an inversion layer is present.
Man-made occurrences like the sound of a passenger aircraft, explosions and other loud sounds appear to sound louder and can be heard further away.
Probably the most important and dangerous consequence of temperature inversion is the trapping of smog and other toxic gasses in a densely populated urban environment or metropolitan area.
Due to the infrastructure and the heat generated by transport and other human activities in a city, heat is absorbed and maintained, only to be slowly released in the atmosphere above the city at night and during cold winter months.
This creates a layer of temperature inversion covering the city. This inversion layer acts as a seal which traps smog, warm air and other toxic emissions in the city.
This not only creates a serious environmental problem but also poses a dangerous and potentially life-threatening situation by keeping these gases from escaping and trapped on the surface and lower atmosphere.
Carbon dioxide, smog, carbon monoxide, and lead are just a few of the chemicals trapped below the inversion layer. All these chemicals have severe and long-term effects on human health and mortality.
You can read all about The Urban Heat Island effect, what causes it, and its effect on the weather and environment in this article.
And now you understand this rebellious phenomenon that likes to buck the trend of meteorological norms called Temperature Inversion.
To be honest though, as the weather is starting to show some startling and peculiar trends during recent years due to more than a hundred years of reckless human interference, it may not stand out as rebellious or unanticipated on its own for much longer.
For now, we need to understand the causes and dangers of temperature inversion, in order to make sure we prevent similar disruptive weather trends from getting established, expanding and become the new norm.
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