2014 Ozone Hole Update
 
Oct 30, 2014: The Antarctic ozone hole reached its annual peak size on
Sept. 11, according to scientists from NASA and the National Oceanic and
Atmospheric Administration (NOAA). The size of this year's hole was 24.1
million square kilometers (9.3 million square miles) - an area roughly the
size of North America.
 
http://www.nasa.gov/sites/default/files/thumbnails/image/ozone_11sept2014.png
 
This image shows ozone concentrations above Antarctica on Sept. 11, 2014.
Image Credit: NASA. See also NASA's Ozone Hole Watch website
 
The single-day maximum area was similar to that in 2013, which reached 24.0
million square kilometers (9.3 million square miles). The largest
single-day ozone hole ever recorded by satellite was 29.9 million square
kilometers (11.5 million square miles) on Sept. 9, 2000. Overall, the 2014
ozone hole is smaller than the large holes of the 1998-2006 period, and is
comparable to 2010, 2012, and 2013.
 
With the increased atmospheric chlorine levels present since the 1980s, the
Antarctic ozone hole forms and expands during the Southern Hemisphere
spring (August and September). The ozone layer helps shield life on Earth
from potentially harmful ultraviolet radiation that can cause skin cancer
and damage plants.
 
The Montreal Protocol agreement beginning in 1987 regulated ozone depleting
substances, such as chlorine-containing chlorofluorocarbons and
bromine-containing halons. The 2014 level of these substances over
Antarctica has declined about 9 percent below the record maximum in 2000.
 
"Year-to-year weather variability significantly impacts Antarctica
ozone because warmer stratospheric temperatures can reduce ozone
depletion," said Paul A. Newman, chief scientist for atmospheres at
NASA's Goddard Space Flight Center in Greenbelt, Maryland. "The ozone
hole area is smaller than what we saw in the late-1990s and early 2000s,
and we know that chlorine levels are decreasing. However, we are still
uncertain about whether a long-term Antarctic stratospheric temperature
warming might be reducing this ozone depletion."
 
http://science.nasa.gov/media/medialibrary/2014/10/30/med6b.jpg
 
The graphs above show the progress of the 2014 ozone hole. The gray shading
indicates the highest and lowest values measured since 1979. The red
numbers are the maximum or minimum observed values. The stratospheric
temperature and the amount of sunlight reaching the south polar region
control the depth and size of the Antarctic ozone hole. [more] Scientists
are working to determine if the ozone hole trend over the last decade is a
result of temperature increases or chorine declines. An increase of
stratospheric temperature over Antarctica would decrease the ozone hole's
area. Satellite and ground-based measurements show that chlorine levels are
declining, but stratospheric temperature analyses in that region are less
reliable for determining long-term trends.
 
Scientists also found that the minimum thickness of ozone layer this year
was recorded at 114 Dobson units on Sept. 30, compared to 250-350 Dobson
units during the 1960s. Over the last 50 years satellite and ground-based
records over Antarctica show ozone column amounts ranging from 100 to 400
Dobson units, which translates to about 1 millimeter (1/25 inch) to 5
millimeters (1/6 inch) of ozone in a layer if all of the ozone were brought
down to the surface.
 
The ozone data come from the Dutch-Finnish Ozone Monitoring Instrument on
NASA's Aura satellite and the Ozone Monitoring and Profiler Suite
instrument on the NASA-NOAA Suomi National Polar-orbiting Partnership
satellite. NOAA measurements at South Pole station monitor the ozone layer
above that location by means of Dobson spectrophotometer and regular
ozone-sonde balloon launches that record the thickness of the ozone layer
and its vertical distribution. Chlorine amounts are estimated using NOAA
and NASA ground measurements and observations from the Microwave Limb
Sounder aboard NASA's Aura satellite.
 
NASA and NOAA are mandated under the Clean Air Act to monitor
ozone-depleting gases and stratospheric depletion of ozone. Scientists from
NASA and NOAA have been monitoring the ozone layer and the concentrations
of ozone-depleting substances and their breakdown products from the ground
and with a variety of instruments on satellites and balloons since the
1970s. These observations allow us to provide a continuous long-term record
to track the long-term and year-to-year evolution of ozone amounts.
 
Credits:
Production editor: Dr. Tony Phillips | Credit: Science{at}NASA
 
 
Regards,
 
Roger

--- D'Bridge 3.99