Ozone hole

Why in news?

• The Antarctic ozone hole — one of the deepest, largest gap in the ozone layer in the last 40 years — has closed, according to World Meteorological Organization (WMO) January 6, 2021.
• The annually occurring ozone hole over the Antarctic had rapidly grown from mid-August and peaked at around 24 million square kilometres — one of the largest so far — in early October 2020. 

About Ozone

• Ozone, made up of three oxygen atoms, occurs naturally in small amounts.
• Roughly 10 km to 40 km up in the atmosphere (the layer called the stratosphere), the ozone layer is a sunscreen, shielding Earth from harmful ultraviolet radiation.
• On the other hand, close to the surface, ozone created as a byproduct of pollution can trigger health problems such as asthma and bronchitis.
• Manufactured chemicals deplete the ozone layer.
• The ozone hole results from ozone-depleting chemicals (e.g. chlorofluorocarbons (CFCs)).
• When CFCs are hit by ultraviolet light, they release chlorine. Chlorine reacts with ozone, destroying it to produce chlorine monoxide and diatomic oxygen.
• These reactions are most effective when they occur on the surface of ice crystals, occurring in Polar Stratospheric Clouds in the stratosphere.

Why there is a larger hole in ozone over Antarctic?

• Polar Stratospheric Clouds occur mostly over the Antarctica than the Arctic region.
• Each spring over Antarctica (it is now spring there), atmospheric ozone is destroyed by chemical processes. This creates the ozone hole, which occurs because of special meteorological and chemical conditions that exist in that region.
• The Southern Hemisphere also receives higher intensity of net insolation because the Perihelion coincides with the Southern Hemisphere summer. This is the period during which the earth is closest to the Sun along its elliptical orbit. This greater intensity of Solar radiation results in breakdown of CFCs into free chlorine atoms that deplete the Ozone layer.
• On the other hand, Ozone depleting gases such as CFCs, HCFCs etc are emitted more from the Northern Hemisphere because of the presence of large industrial zones and highly populated regions.

Prelims Question

Consider the following statements regarding Ozone Hole:
1.The annual ozone hole is usually larger over the south pole region compared to north pole region.
2.In warmer temperatures, more polar stratospheric clouds form and they helps in ozone-formation process. 
Which of the statements given above is/are correct?
(a)1 only
(b)2 only
(c)Both 1 and 2
(d)Neither 1 nor 2

 Answer to prelims question