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| |  | | | | NASA's Aura Satellite Peers Into Earth's Ozone Hole
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12.07.05
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NASA researchers, using data from the agency's AURA satellite, determined
the seasonal ozone hole that developed over Antarctica this year is smaller
than in previous years.
Image above:The annual "ozone hole" over Antarctica this year reached its largest area on Sept. 11. Observations are from the Ozone Monitoring Instrument on NASA's Aura satellite, launched in 2004. Blue and purple areas represent low ozone levels. (+ Download High-Res .jpg) Credit: NASA
NASA's 2005 assessment of the size and thickness of the ozone layer was the
first based on observations from the Ozone Monitoring Instrument on the
agency's Aura spacecraft. Aura was launched in 2004.
This year's ozone hole measured 9.4 million square miles at its peak
between September and mid-October, which was slightly larger than last
year's peak. The size of the ozone hole in 1998, the largest ever recorded,
averaged 10.1 million square miles. For 10 of the past 12 years, the
Antarctic ozone hole has been larger than 7.7 million square miles. Before
1985, it measured less than 4 million square miles.
 Image right: The 2005 Antarctic ozone hole was breaking up and shrinking on Nov. 8 when these observations were made by NASA's Aura satellite. The region of low ozone (blue and purple) moved over the tip of South America. (+ Download High-Res .jpg) Credit: NASA
The protective ozone layer over Antarctica annually undergoes a seasonal
change, but since the first satellite measurements in 1979, the ozone hole
has gotten larger. Human-produced chlorine and bromine chemicals can lead
to the destruction of ozone in the stratosphere. By international
agreement, these damaging chemicals were banned in 1995, and their levels
in the atmosphere are decreasing.
Another important factor in how much ozone is destroyed each year is the
temperature of the air high in the atmosphere. As with temperatures on the
ground, some years are colder than others. When it's colder in the
stratosphere, more ozone is destroyed. The 2005 ozone hole was
approximately 386,000 square miles larger than it would have been in a year
with normal temperatures, because it was colder than average. Only twice in
the last decade has the ozone hole shrunk to the size it typically was in
the late 1980s. Those years, 2002 and 2004, were the warmest of the period.
 Image left: The 2005 Antarctic ozone hole grows and eventually fades away between July and November in this animation of its seasonal cycle. The ozone hole this year was slightly larger in area than North America, measuring 9.4 million square miles (24 million square kilometers) The size of the ozone hole in 1998, the largest ever recorded, averaged 10.1 million square miles (26.1 million square kilometers). Blues and purples represent low ozone; greens, yellows and red represent where there is more ozone. Click on image to open a daily composite video of this years ozone hole. Credit: NASA
Scientists also monitor how much ozone there is in the atmosphere from the
ground to space. The thickness of the Antarctic ozone layer was the third
highest of the last decade, as measured by the lowest reading recorded
during the year. The level was 102 Dobson Units (the system of measurement
designated to gauge ozone thickness). That is approximately one-half as
thick as the layer before 1980 during the same time of year.
The Ozone Monitoring Instrument is the latest in a series of
ozone-observing instruments flown by NASA over the last two decades. This
instrument provides a more detailed view of ozone and is also able to
monitor chemicals involved in ozone destruction. The instrument is a
contribution to the mission from the Netherlands' Agency for Aerospace
Programs in collaboration with the Finnish Meteorological Institute. The
Royal Netherlands Meteorological Institute is the principal investigator on
the instrument.
Rob Gutro
NASA Goddard Space Flight Center
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