Satellite Data Reveals Slight Shrinking Of Antarctic Ozone Hole
[ Watch The Video: Daily Ozone Hole for 2013 ]
redOrbit Staff & Wire Reports – Your Universe Online
The Antarctic ozone hole, a seasonal phenomenon that starts forming during the month of August was slightly smaller this year than it was on average over the past several decades, NASA satellite data has revealed.
The average size of the ozone hole in September-October 2013 was 8.1 million square miles (21 million square kilometers), the US space agency reported on Friday.
In comparison, the average size since the mid-1990s (when the annual maximum size of the hole stopped growing) is 8.7 million square miles (22.5 million square kilometers). However, scientists claim that the single-year size change is not enough data to determine whether or not the phenomenon has started to heal.
“There was a lot of Antarctic ozone depletion in 2013, but because of above average temperatures in the Antarctic lower stratosphere, the ozone hole was a bit below average compared to ozone holes observed since 1990,” Paul Newman, an atmospheric scientist and ozone expert at NASA’s Goddard Space Flight Center in Maryland, said in a statement.
The formation of the ozone hole begins during Antarctic spring each year, when the sun starts rising following several months of winter darkness. Cold air is trapped above the continent by polar-circling winds, and sunlight serves as a catalyst for reactions involving ice clouds and chlorine from manmade chemicals. Those reactions deplete the ozone until early December, when they wind down and allow the seasonal hole to eventually close.
“Levels of most ozone-depleting chemicals in the atmosphere have gradually declined as the result of the 1987 Montreal Protocol, an international treaty to protect the ozone layer by phasing out production of ozone-depleting chemicals,” NASA explained. “As a result, the size of the hole has stabilized, with variation from year to year driven by changing meteorological conditions.”
“The single-day maximum area this year was reached on Sept. 16 when the maximum area reached 9.3 million square miles (24 million square kilometers), about equal to the size of North America,” it added. “The largest single-day ozone hole since the mid-1990s was 11.5 million square miles (29.9 million square kilometers) on Sept. 9, 2000.”
NASA and National Oceanic and Atmospheric Administration (NOAA) scientists have been using a variety of ground, satellite-based and balloon-based instruments to monitor the ozone layer for approximately five decades. Each of those instruments collects data regarding different aspects of ozone depletion.
“The independent analyses ensure that the international community understands the trends in this critical part of Earth’s atmosphere. The resulting views of the ozone hole have differences in the computation of the size of the ozone hole, its depth, and record dates,” the US space agency said.
NASA’s 2013 observations of the ozone hole were obtained from data supplied by instruments on the agency’s Aura satellite, as well as the Ozone Monitoring and Profiler Suite instrument on the NASA-NOAA Suomi National Polar-orbiting Partnership satellite. Among the long-term satellite-based ozone-monitoring instruments used to monitor the hole are the Total Ozone Mapping Spectrometer, the second generation Solar Backscatter Ultraviolet Instrument, the Stratospheric Aerosol and Gas Experiment series of instruments, and the Microwave Limb Sounder.