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)