The Ozone Hole

All life on Earth depends on the existence of a thin shield of a poisonous gas high in the atmosphere: the ozone layer.
(Ozone Secretariat, UNEP, “Action on Ozone”)

The ozone layer is a region of our atmosphere widely known for absorbing a large part of the direct dangerous ultraviolet radiation coming from the Sun. Indeed UV exposition can affect our immune system, damage our skin and eyes and impact on marine life. In this respect the ozone layer, composed by an high concentration of the homonym gas, is basically acting as a shield protecting the Earth and being of crucial importance for the equilibrium of the atmosphere.

A the end of 1970s several aspects related to the ozone layer started to be observed, leading to the discovery of the so called ozone depletion. This phenomenon consists of two different events, namely a lowering of the total amount of the gas concentration in the atmosphere and a much larger springtime decrease in the stratospheric ozone around Earth’s polar regions. This second one phenomenon is referred to as the ozone hole.

Ozone Hole (Nov 2018) – O3 Total Column – Stereographic South Pole

The discovery of the Antarctic ozone hole was firstly reported in the 1985 by two British scientists and came as a shock to the scientific community, because the observed decline in polar ozone was far larger than anyone had anticipated. Satellite measurements showing massive depletion of ozone around the poles were becoming available with good frequency and nowadays the Copernicus Sentinel-5p mission, thanks to the high revisit time and wide swath, is giving continuity to this purpose.

In the two showed images we can see in two particular projections the ozone total column concentration over the atmosphere. The gas concentration is expressed in Dobson Units (DU), a unit of measurement of the amount of a trace gas in a vertical column: lower is the DU, lower is the concentration. The atmospheric region over the Antarctica shows the lowest values, thus highlighting the hole as we can see in the image above in a the stereographic south pole projection. The image has been processed using 7 days of consecutive Sentinel-5P acquisition in November 2018, in the middle of the southern hemisphere’s spring where the ozone hole concentration can reach around 100 DU.

Ozone Worldwide (Nov 2018) – O3 Total Column – Mollweide Projection

The primary cause of the ozone depletion is linked to the presence in the atmosphere of specific gases, namely CFCs and halocarbons. Human activities cause the emission of those gases in the Earth atmosphere and in presence of UV light specific reactions are triggered, thus leading to the ozone depletion. Those substances are present throughout all the ozone layer but the depletion on the Antarctic region occurs because of the special atmospheric and chemical conditions that exist only there. One of them is related to the formation of clouds in the cold Antarctic stratosphere that increases the amount of chlorine present in ozone-destroying forms, thus producing the hole in southern hemisphere springtime (September to December).

Earth Starts Beating started to monitor the ozone layer with monthly Sentinel-5p maps published via our ESB browserin order to offer the community a systematic and frequent overview of its depletion through the seasons and through the years. All the images contains Copernicus modified data and are processed in ONDA.

References:

[1] https://www.ozonelayer.noaa.gov/science/basics.htm

[2] http://www.tropomi.eu/data-products/total-ozone-column

[3] https://sciencing.com/about-6453516-uv-light-harmful-.html

[4] https://sentinel.esa.int/documents/247904/3541451/Sentinel-5P-Readme-OFFL-Total-Ozone.pdf

[5] https://acd-ext.gsfc.nasa.gov/Documents/O3_Assessments/Docs/WMO_2010/Q2_QA.pdf

[6] https://www.researchgate.net/publication/246650409_Large_Losses_of_Total_Ozone_in_Antarctica_Reveal_Seasonal_ClOxNOx_Interaction

[7] http://www.faqs.org/faqs/ozone-depletion/antarctic/

[8] https://esrl.noaa.gov/csd/assessments/ozone/2006/chapters/Q7.pdf

[9] https://uk-air.defra.gov.uk/research/ozone-uv/moreinfo?view=antarctica-hole-explained

 

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.