Why is the ozone hole concentrated in Antarctica?

Have you ever wondered why when mentioning the hole in the ozone layer people often associate with Antarctica? Or why the hole does not appear in places where many dangerous emissions are released?

The serious depletion of the stratosphere in the late winter and early spring in Antarctica, commonly known as "", was first discovered in Antarctica in 1985. Since then this problem has always been a global concern. .

Here are the reasons why this hole often appears in Antarctica.

Halogen collection

Some compounds contain halogen, especially CFC gas, from the ground will move to the stratosphere by wind and air convection. This activity occurs in both hemispheres despite the majority of emissions in the northern hemisphere.

The smallest ozone layer vulnerability has been announced by NASA this month - (Photo: NASA).

The gases that damage the ozone layer are quite large and can travel a long way to the stratosphere. The reason is that they are difficult to "eliminate" naturally in the lower atmosphere.

Hazardous compounds enter the stratosphere mainly from the tropics, then transfer to the two poles due to the impact of the stratosphere air.

Low temperature

The necessary conditions for ozone depletion are low temperatures in the stratosphere that span a large area and last a long time.

Low temperatures allow polar stratospheric clouds to form, also called nacreous clouds (abbreviated: PSC). This is the environment for reactions to destroy ozone layer.

The lowest stratosphere temperature on Earth at 2 poles in winter. However, winter in Antarctica is generally colder and more stable than in the Arctic winter.

Antarctic temperatures help PSC form longer during the winter for about 5 months compared to a period of only 10 to 60 days in the Arctic.

 

Nacreous clouds formed in Antarctica - (Photo: NASA).

Nacreous cloud is a kind of cloud in the polar stratosphere of winter at a height of about 15,000 - 25,000m, which helps to support chemical reactions that create chlorine monoxide (ClO), the main cause of ozone depletion.

Unlike the troposphere, the stratosphere is very dry and it rarely allows cloud formation. However, in extreme cold conditions of polar winter, stratospheric clouds of different types can be formed.

The most common type of PSC is formed from HNO ₃ and water and occasionally contains some drops of H ₂ SO ₄ .

As the average temperature begins to increase at the end of winter, PSC forms less and produces less ClO. And when PSC doesn't happen again, usually before the end of January or early February in the Arctic and in mid-October in Antarctica, the most destructive phase of the ozone layer ends.

HNO ₃ gas

Once formed, molecules in the PSC often fall to a lower height due to gravity. The largest molecules can fall a few kilometers in the stratosphere during the cold winter months of Antarctica.

PSC contains a very high ratio of HNO ₃ , thus lowering elevation contributes to release HNO ₃ . This process is called nitrification in the stratosphere.

Less HNO ₃ while ClO still exists in high quantities increases the ability to destroy the ozone layer.

Nitrification problems are often severe every spring in Antarctica and a few other places but not in the Arctic because the temperature influences PSC's nitrification process must be stable in a large and extant high altitude. in for a long time.