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Ozone hole modest despite optimal conditions for ozone depletion



The ozone hole that formed in the upper atmosphere of the Antarctic each September was slightly above average in 2018, reported NOAA and NASA scientists.

Above-average low temperatures in the Antarctic stratosphere created ideal conditions for the destruction of ozone this year, but a decline in ozone-depleting chemicals prevented the hole from being as large as it would have been 20 years ago.

"Chlorine levels in the Antarctic stratosphere have fallen by about 11 percent since the peak year of 2000," said Paul A. Newman, chief geoscientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "The colder temperatures this year would have given us a much larger ozone hole if the chlorine in 2000 was still at a level."

According to NASA, the annual ozone hole reached an average area coverage of 8.83 million square miles (22.9 square kilometers) in 201

8, nearly three times the size of the adjacent United States. It is the 13th largest of 40 years of NASA satellite observations. Nations of the world began in 1987 to phase out the use of ozone-depleting substances under an international agreement known as the Montreal Protocol.

The 2018 ozone hole was heavily influenced by a stable and cold Antarctic vortex – the stratospheric low-pressure system flows clockwise into the atmosphere above the Antarctic. These colder conditions – in the coldest conditions since 1979 – helped to create polar stratospheric clouds whose cloud particles activate ozone-depleting forms of chlorine and bromine compounds.

In 2016 and 2017, warmer temperatures limited the formation of polar stratospheric clouds and slowed the growth of the ozone hole. In 2017, the ozone hole reached a size of 19.6 km ², before it began to recover. In 2016, the hole grew to 8 million square miles (20.7 square kilometers).

However, the current ozone hole area is still large compared to the 1980s when ozone depletion over Antarctica was first discovered. The atmospheric levels of man-made ozone-depleting substances increased until the year 2000. Since then, they have slowly declined, but they remain high enough to cause significant ozone loss.

According to NOAA scientists, the colder temperatures could be almost completely eliminated in 2018. Ozone in a deep, 5 km long layer above the South Pole. In this layer, active chemical degradation of ozone takes place in polar stratospheric clouds. Ozone levels at the South Pole reached a minimum of 104 Dobson units on October 12, making it the 12th lowest year in 33 years for measuring NOAA ozone probes at the South Pole, according to NOAA scientist Bryan Johnson.

"Even under this year's optimal conditions, ozone loss at upper altitudes was less strong, which we would expect given the decreasing stratospheric chlorine levels," Johnson said.

A Dobson unit is the standard measurement for the total amount of ozone in the atmosphere above a point on the earth's surface, and it indicates the number of ozone molecules required to reach a temperature of 0 ° C (0 ° C) C) a pure ozone layer at a temperature of 0 ° C to produce atmospheric pressure that corresponds to the Earth's surface. A value of 104 Dobson units would be a 1.04 millimeter thick layer at the surface, less than the thickness of a dime.

Before the appearance of the Antarctic ozone hole in the 1970s, the average amount of ozone was above September and October, the South Pole was between 250 and 350 Dobson units.

What is ozone and why is it important?

Ozone consists of three oxygen atoms and is very reactive with other chemicals. In the stratosphere, about 11 to 40 kilometers (11 to 40 kilometers) above the surface, an ozone layer acts like sunscreen, protecting the planet from ultraviolet radiation that can cause skin cancer and cataracts, suppress the immune system, and damage plants. Ozone can also be produced by photochemical reactions between the sun and pollution from vehicle emissions and other sources that form harmful smog in the lower atmosphere.

NASA and NOAA use three complementary instrumental methods to monitor the growth and breakup of the ozone hole year. Satellite instruments such as NASA's Aura Satellite ozone monitoring instrument and NASA's NOAA Suomi National Ozone Mapping Profiler Suite measure ozone over large areas of space. The Aura Satellite's Microwave Limb Sounder also measures certain chlorine-containing gases and provides estimates of the total chlorine content.

The total amount of ozone in the atmosphere is extremely low. All the ozone in a column of the atmosphere that extends from the ground into space would be 300 Dobson units, about the thickness of two pennies stacked on top of each other.

NOAA scientists monitor the thickness of the ozone layer and its ozone layer vertical distribution above the South Pole by periodically firing weather balloons with ozone probes up to a height of 34 km and using a ground-based instrument called the Dobson spectrophotometer.

Related Links

Goddard Ozone Watch

Earth Observation News – Suppiliers, Technology and Application



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