The Ozone Hole of 2010 was the second smallest in over a decade. It reached it’s
largest size of 22.6 million square kilometers on September 25,2010 which is
below the decade average of 25.7 million square kilometers.
Ozone values reached the lowest point at 118 Dobson Units on October 1, 2010 .
The year-to-year variation in the size of the ozone hole is mainly related to
the weather conditions in the polar stratosphere. The warmer conditions that
prevailed over Antarctica in the winter of 2010 resulted in a smaller ozone hole
as compared to previous years.
MACC – Monitoring Atmospheric
Composition and Climate-The destruction of ozone in the ozone layer over
Antarctica this year is about 40 to 60% less compared to the previous five
years, according to MACC analyses based on observations from the SCIAMACHY
instrument on board the European ENVISAT satellite. Less ozone destruction is
consistent with the expectation that the ozone layer will recover during the
coming decades due to reduction in the stratospheric amount of chlorine.
However, such a large change cannot be attributed to the slow decrease of
stratospheric chlorine of 0.5-1% per year. This year’s reduced ozone destruction
turns out to be caused by unusual meteorological conditions.
Sudden Stratospheric Warming
In July and August a phenomenon known as a Sudden Stratospheric Warming occurred
in the stratosphere above Antarctica: a sudden fast warming in the ozone layer.
The stratosphere is the atmospheric layer between 15 and 35 km altitude which
contains large amounts of ozone that protects us from harmful ultraviolet
radiation. The exact mechanisms of these of warmings are still not fully
understood, but they happen quite often and have their origin in the
troposphere, the lowest layer of the atmosphere where our weather occurs.
Effect of nitrogen-oxides on
chlorine release
The ozone hole appears because of the destructive power of chlorine which is
present in the ozone layer but under normal conditions chemically bonded with
nitrogen-oxides. However, via complex chemical processes the chlorine can be
released during the polar winter above Antarctica. At temperatures below -78°C
the nitrogen-oxides are removed from the stratosphere. The remaining chlorine
can no longer be bonded and when the sun becomes stronger during spring the
chlorine can start to do its damaging work.
Although the temperature in the
Antarctic stratosphere sinks below -78°C every July and August, it does not get
much colder. A small temperature rise of only a few degrees thus can result in
considerably more nitrogen-oxides remaining in the stratosphere, and thus less
effective ozone destruction. Recent measurements of the American MLS instrument
on the AURA satellite indeed show that there are still nitrogen-oxides present
in the stratosphere above Antarctica, unlike previous years.
Late onset of ozone desctruction
in 2010
This year’s ozone destruction consequently only started to become visible during
September, whereas under normal conditions the first signs already become
visible about halfway through August. The observations by SCIAMACHY show that
the amount of ozone decreased steadily towards October, but the destruction
continued to lag behind that of previous five years. At the beginning of October
the amount of ozone destruction was still 40-60% less than in a typical year. In
the second half of October the ozone loss became more comparable to previous
years. Ozone destruction usually ceases in October after which the ozone hole
starts to fill up.
Not the first time
Studying historical satellite observations shows that Sudden Stratospheric
Warmings occur quite often. In 2002 there was a particularly large warming that
caused the ozone hole to split and disappear already in September. In 1988 there
was a sudden stratospheric warming in July and August comparable to this year’s,
and also then the first signs of ozone destruction became visible only during
September. Small temperature changes the Antarctic stratosphere in July and
August of only a few degrees can still have a large impact on the formation of
the ozone hole. Such events very much complicate efforts to determine if the
expected ozone hole recovery has started.
Ozone values over parts of the
Antarctic Peninsula fell rapidly rapidly to around 240 DU in the first half of
July, but then recovered. By early August the ozone hole had begun to
form, though it was a slow start to the season and significant depletion did not
commence until towards the end of the month. Ozone values at Rothera fell
below the ozone hole threshold for the first time on August 17, but then
recovered. The ozone hole was at its largest in late September at
around 20 million square kilometres, which was well below the average size of
the last decade. This slow start and relatively shallow ozone hole was
linked to warmer than usual stratospheric temperatures reducing the volume of
stratospheric clouds early in the season. Since its peak the ozone hole
has slowly declined in area and is now around 10 million square kilometres,
which is a record size for this time of year. The ozone hole has been
slowly filling, with lowest ozone values now around 190 DU, broadly over the
pole. Filling is expected to proceed more rapidly over the coming week with
levels rising above 220 DU. In the belt surrounding Antarctica outside the
polar vortex ozone, values are slowly declining from their peak of a little
above 400 DU. The polar vortex has passed its largest area, which was
slightly above the average area of the last decade and at 70hPa remains much
larger than the average for this time of year and is near record in size.
The temperature of the ozone layer within it was at the winter minimum in August
but is rising, with stratospheric temperatures now higher than the PSC formation
threshold, albeit rising more slowly than usual. The fringes of the ozone
hole extended over the tip of South America and South Georgia over September 6 –
9, 16 – 21, October 10 – 12 and18 – 23.
Ozone values over parts of the
Antarctic Peninsula fell rapidly rapidly to around 240 DU in the first half of
July, but then recovered. By early August the ozone hole had begun to
form, though it was a slow start to the season and significant depletion did not
commence until towards the end of the month. Ozone values at Rothera fell
below the ozone hole threshold for the first time on August 17, but then
recovered. The ozone hole was at its largest in late September at
around 20 million square kilometres, which was well below the average size of
the last decade. It has now shrunk to around 12 million square kilometres,
a little larger than the average for this time of year over the last decade.
Lowest ozone values are centred over the Pensacola Mountains. In the belt
surrounding Antarctica outside the polar vortex ozone, values are slowly
declining from their peak of a little above 400 DU. The polar vortex has
passed its largest area, which was slightly above the average area of the last
decade and at 70hPa remains a little larger than the average for this time of
year. The temperature of the ozone layer within it has passed the
late winter minimum and is slowly rising. Above 50 hPa temperatures are
higher than the PSC threshold and the volume capable of forming polar
stratospheric clouds (PSCs) is now very small. The fringes of the ozone
hole extended over the tip of South America and South Georgia over September 6 –
9, 16 – 21, October 10 – 12 and18 – 23.
Ozone values over parts of the
Antarctic Peninsula fell rapidly rapidly to around 240 DU in the first half of
July, but then recovered. By early August the ozone hole had begun to
form, though it was a slow start to the season and significant depletion did not
commence until towards the end of the month. Ozone values at Rothera fell
below the ozone hole threshold for the first time on August 17, but then
recovered. The ozone hole was at its largest in late September at
around 20 million square kilometers, which was well below the average size of
the last decade. It has now shrunk to around 17 million square kilometers,
a little larger than the average for this time of year over the last decade.
Lowest ozone values are centred over Dronning Maud Land. In the belt
surrounding Antarctica outside the polar vortex ozone, values are slowly
declining from their peak of a little above 400 DU. The polar vortex has
passed its largest area, which was slightly above the average area of the last
decade and at 70hPa remains a little larger than the average for this time of
year. The temperature of the ozone layer within it has passed the
late winter minimum and is slowly rising. Above 50 hPa temperatures are
higher than the PSC threshold and the volume capable of forming polar
stratospheric clouds (PSCs) is now very small. The fringes of the ozone
hole extended over the tip of South America and South Georgia over September 6 –
9, 16 – 21, October 10 – 12 and18 – 23.
Ozone values over parts of the
Antarctic Peninsula fell rapidly rapidly to around 240 DU in the first half of
July, but then recovered. By early August the ozone hole had begun to
form, though it was a slow start to the season and significant depletion did not
commence until towards the end of the month. Ozone values at Rothera fell
below the ozone hole threshold for the first time on August 17, but then
recovered. The ozone hole was at its largest in late September at
around 20 million square kilometres, which was well below the average size of
the last decade. It has now shrunk to around 18 million square kilometres.
Lowest ozone values are slightly offset from the South Pole towards the Atlantic
sector and overall values are near their lowest. The fringes of the ozone
hole extended over the tip of South America and South Georgia over September 6 –
9 and again from 16 – 21. In the belt outside the polar vortex
surrounding Antarctica ozone values are near their highest, with some areas
above 400 DU. On a few occasions the polar vortex has moved sufficiently
towards the Atlantic sector to allow these high ozone areas to move over the
continental fringes of the Pacific sector. The polar vortex has passed its
largest area, which was slightly above the average area of the last decade and
at 70hPa remains a little larger than the average for this time of year .
The temperature of the ozone layer within it has passed the late winter minimum,
with the area capable of forming polar stratospheric clouds (PSCs) now near the
average of the last decade. Polar stratospheric clouds are however still
widespread.
Ozone values over parts of the
Antarctic Peninsula fell rapidly rapidly to around 240 DU in the first half of
July, but then recovered. By early August the ozone hole had begun to
form, though it was a slow start to the season. Ozone values at Rothera
fell below the ozone hole threshold for the first time on August 17, but then
recovered. The ozone hole is now near its largest, but at an
estimated 19 million square kilometres it is below the average size of the last
decade. Lowest ozone values are broadly centred on the South Pole and
overall values are nearing their lowest. The fringes of the ozone hole
extended over the tip of South America and South Georgia over September 6 – 9
and again from 16 – 21. In the belt outside the polar vortex
surrounding Antarctica ozone values are near their highest, with some areas
above 400 DU. On a few occasions the polar vortex has moved sufficiently
towards the Atlantic sector to allow these high ozone areas to move over the
continental fringes of the Pacific sector. The polar vortex has passed its
largest area, which was slightly above the average area of the last decade and
is now close to the average for this time of year at 70hPa. The
temperature of the ozone layer within it has passed the late winter minimum,
with the area capable of forming polar stratospheric clouds (PSCs) smaller than
the average of the last decade. Polar stratospheric clouds are however
widespread.
Ozone values over parts of the
Antarctic Peninsula fell rapidly rapidly to around 240 DU in the first half of
July, but then recovered. By early August the ozone hole had begun to
form, though it was a slow start to the season. Ozone values at Rothera
fell below the ozone hole threshold for the first time on August 17, but then
recovered. Low ozone values are currently seen over a wide swathe of
the continent. An increasing area is below the ozone hole threshold, but
at an estimated 19 million square kilometres it is well below the average size
of the last decade. The fringes of the ozone hole extended over the tip of
South America and South Georgia over September 6 – 9 and again from 16 – 21.
Around Antarctica ozone values are near their highest, with some areas above 400
DU. On a few occasions the polar vortex has moved sufficiently towards the
Atlantic sector to allow these high ozone areas to move over the continental
fringes of the Pacific sector. The polar vortex has passed its largest
area, which was slightly above the average area of the last decade and is now
close to the average for this time of year. The temperature of the
ozone layer within it has passed the late winter minimum, with the area capable
of forming polar stratospheric clouds (PSCs) smaller than the average of the
last decade. Polar stratospheric clouds are however widespread.
Ozone values over parts of the
Antarctic Peninsula fell rapidly rapidly to around 240 DU in the first half of
July, but then recovered. By early August the ozone hole had begun to
form. Ozone values at Rothera fell below the ozone hole threshold for the
first time on August 17, but then recovered. Lowest ozone values are
currently seen in a wide ellipse across Antarctica extending into the Weddell
Sea. An increasing area is below the ozone hole threshold, but at an
estimated 14 million square kilometres it is substantially below the average of
the last decade. The fringes of the ozone hole have extended over the tip
of South America and South Georgia in the last few days. Around Antarctica
ozone values are building, with some areas above 400 DU. On a few
occasions the polar vortex has moved sufficiently towards the Atlantic sector to
allow these high ozone areas to move over the continental fringes of the Pacific
sector. The polar vortex appears to have passed its largest area, which
was slightly above the average area of the last decade but is now smaller than
the average for this time of year. The temperature of the ozone
layer within it is nearing the late winter minimum, but the area capable of
forming polar stratospheric clouds (PSCs) is smaller than the average of the
last decade. Polar stratospheric clouds are however widespread.
Ozone values over parts of the
Antarctic Peninsula fell rapidly rapidly to around 240 DU in the first half of
July, but then recovered. By early August the ozone hole had begun to
form. Ozone values at Rothera fell below the ozone hole threshold for the
first time on August 17, but then recovered. Lowest ozone values are
currently seen over Terre Adelie, where they are near the ozone hole threshold.
Elsewhere over Antarctica ozone values are generally below 270 DU. Around
Antarctica ozone values are building, with some areas above 400 DU. On a
few occasions the polar vortex has moved sufficiently towards the Atlantic
sector to allow these high ozone areas to move over the continental fringes of
the Pacific sector. The polar vortex appears to have passed its largest
area, which was slightly above the average area of the last decade but is now
smaller than the average for this time of year. The temperature of
the ozone layer within it is nearing the late winter minimum, but the area
capable of forming polar stratospheric clouds (PSCs) is smaller than the average
of the last decade. Polar stratospheric clouds are however widespread.
Ozone values over parts of the
Antarctic Peninsula fell rapidly rapidly to around 240 DU in the first half of
July, but then recovered. By early August the ozone hole had begun to
form. Ozone values at Rothera fell below the ozone hole threshold for the
first time on August 17. Lowest ozone values are currently seen over
the base of the Antarctic Peninsula. Elsewhere over Antarctica ozone
values are generally above 250 DU. Around Antarctica ozone values are
building, with some areas above 400 DU. On a few occasions the polar
vortex has moved sufficiently towards the Atlantic sector to allow these high
ozone areas to move over the continental fringes of the Pacific sector.
The polar vortex is near its largest and slightly above the average area of the
last decade. The temperature of the ozone layer within it is nearing
the late winter minimum, but the area capable of forming polar stratospheric
clouds (PSCs) is smaller than the average of the last decade. Polar
stratospheric clouds are however widespread.
Ozone values over parts of the
Antarctic Peninsula fell rapidly rapidly to around 240 DU in the first half of
July, but then recovered. By early August the ozone hole had begun to
form, with low values stretching from Ellsworth Land to Dronning Maud Land.
Elsewhere over Antarctica ozone values are generally above 250 DU. Around
Antarctica ozone values are building, with some areas approaching 400 DU.
On a few occasions the polar vortex has moved sufficiently towards the Atlantic
sector to allow these high ozone areas to move over the continental fringes of
the Pacific sector. The polar vortex is still growing and the temperature
of the ozone layer within it is still cooling towards its late winter minimum.
It is slightly larger and colder than at this time last year. Polar
stratospheric clouds (PSCs) are widespread.
Ozone values over parts of the
Antarctic Peninsula fell rapidly rapidly to around 240 DU in the first half of
July, but then recovered. By early August the ozone hole had begun to
form, with low values stretching from Ellsworth Land to Dronning Maud Land.
Elsewhere over Antarctica ozone values are generally above 250 DU. Around
Antarctica ozone values are building, with some areas approaching 400 DU.
On a few occasions the polar vortex has moved sufficiently towards the Atlantic
sector to allow these high ozone areas to move over the continental fringes of
the Pacific sector. The polar vortex is still growing and the temperature
of the ozone layer within it is still cooling towards its late winter minimum.
It is slightly larger and colder than at this time last year. Polar
stratospheric clouds (PSCs) are widespread.
