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 
romine-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@NASA
 
 
Regards,
 
Roger

--- D'Bridge 3.99
 * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)