18 October 2007-NASA-Data from NASA’s Earth-observing Aura satellite show that
the ozone hole peaked in size on Sept. 13,2007 reaching a maximum area extent of
9.7 million square miles(24.7Area (million sq. km)) just larger than the size
of North America. That’s “pretty average,” says Paul Newman, an atmospheric
scientist at NASA Goddard Space Fight Center, when compared to the area of ozone
holes measured over the last 15 years. Still, the extent this year was “very
big,” he says, compared to 1970s when the hole did not yet exist.
2007 ozone hole ‘smaller than usual’
3 October 2007 ESA-The ozone hole over Antarctica has shrunk 30 percent as
compared to last year’s record size. According to measurements made by ESA’s
Envisat satellite, this year’s ozone loss peaked at 27.7 million tonnes,
compared to the 2006 record ozone loss of 40 million tonnes. Ozone loss is
derived by measuring the area and the depth of the ozone hole. The area of this
year’s ozone hole – where the ozone measures less than 220 Dobson Units – is
24.7 million sq km, roughly the size of North America, and the minimum value of
the ozone layer is around 120 Dobson Units. A Dobson Unit is a unit of
measurement that describes the thickness of the ozone layer in a column directly
above the location being measured. For instance, if an ozone column of 300
Dobson Units is compressed to 0º C and 1 atmosphere (the pressure at the Earth’s
surface) and spread out evenly over the area, it would form a slab of ozone
approximately 3mm thick.
Scientists say this year’s smaller hole – a thinning in the ozone layer over the
South Pole – is due to natural variations in temperature and atmospheric
dynamics (illustrated in the time series to the right) and is not indicative of
a long-term trend. “Although the hole is somewhat smaller than usual, we cannot
conclude from this that the ozone layer is recovering already,” Ronald van der
A, a senior project scientist at Royal Dutch Meteorological Institute (KNMI),
said. “This year’s ozone hole was less centred on the South Pole as in other
years, which allowed it to mix with warmer air, reducing the growth of the hole
because ozone is depleted at temperatures less than -78 degrees Celsius.”
Southern Hemisphere Winter
2007 Summary NOAA Climate Prediction Center-Extensive ozone depletion was
again observed over Antarctica during the Southern Hemisphere winter of 2007,
with widespread total ozone anomalies of 45 percent or more below the 1979 to
1986 base period. The area covered by extremely low total ozone values of less
than 220 Dobson Units, defined as the Antarctic “Ozone Hole” area, in September
reached maximum size of greater than 24 million square kilometers, the 7th
largest over all 29 years of continuous satellite monitoring of Antarctic ozone.
However, after reaching its maximum size, the Ozone Hole diminished in size such
that it was just the 17th largest for the month of October. Vertical profiles of
ozone amounts, measured by balloon-sondes over the South Pole, showed
near-complete destruction of ozone in the 13 to 21 km region for a relatively
short period of time due to the Ozone Hole’s displacement off of the pole
towards the Atlantic quadrant. Minimum total ozone values observed at the South
Pole were higher than those seen during recent years. Lower stratospheric
temperatures over the Antarctic region in the winter of 2007 were again well
below -78ºC, and were sufficiently low for polar stratospheric cloud formation,
promoting chemical ozone loss. The size of the area of very low temperatures in
2007 was, however, average or below average for the past ten years. The polar
vortex persisted until mid-December when it and the remains of the Ozone Hole
slowly diminished as the polar circulation changed over into its summer pattern.
Very low ozone values were again
observed over Antarctica in the Winter of 2007. Ozone depletion greater than 45%
was observed over Antarctica, compared to total ozone amounts observed in the
early 1980’s. Vertical soundings over the South Pole during September and
October 2007 showed near-complete destruction of ozone at altitudes between 13
and 21 km. Lower stratosphere temperatures in the winter of 2007 over the
Antarctic region were near average levels. Associated with this, the peak size
of the Ozone Hole was smaller than the record breaking sizes seen this past
decade. Other characteristics of the 2007 Ozone Hole are that it was near the
10-year average or below it for a major fraction of its existence, it was off
center from the South Pole for most of September and October, but due to the
persistence of the polar vortex once it re-centered over the South Pole, the
Ozone Hole itself persisted well into December.
Observations of
chlorofluorocarbons and of stratospheric hydrogen chloride support the view that
international actions are reducing the use and release of ozone depleting
substances (WMO, 1999; Anderson et al., 2000). However, chemicals already in the
atmosphere are expected to continue to impact the ozone amount for many decades
to come. The Antarctic Ozone Hole is expected to continue for decades. Antarctic
ozone abundances are projected to return to pre-1980 levels around 2060-2075,
roughly 10-25 years later than estimated in the 2002 Assessment. The projection
of this later return is primarily due to a better representation of the time
evolution of ozone-depleting gases in the Polar Regions. In the next two
decades, the Antarctic Ozone Hole is not expected to improve significantly (WMO,
2006). Further, changing conditions (i.e. meteorological, solar, and volcanic
aerosols) that modulate ozone can complicate the task of detecting the start of
ozone layer recovery. The eruption of the Pinatubo volcano provided an example
of such a complication in the 1990s. Based on an analysis of 10 years of South
Pole ozone vertical profile measurements, Hofmann et al., (1997) estimated that
recovery in the Antarctic Ozone Hole may be detected as early as the coming
decade. Indicators include: 1) an end to springtime ozone depletion at 22-24 km,
2) 12-20 km mid-September column ozone loss rate of less than 3 DU per day, and
3) a 12-20 km ozone column of more than 70 DU on September 15. An intriguing
aspect of recent observations of the Antarctic stratosphere had been the
apparent trend towards a later breakup of the vortex in years since 1990,
relative to the 1980s. The size and duration and size of the 2007 Ozone Hole is
attributed in part to meteorological conditions. A full explanation of such
meteorological anomalies is not yet available. Continued monitoring and
measurements, including total ozone and its vertical profile, are essential to
achieving the understanding needed to identify ozone recovery.
Situation at 2007
December 28
British Antarctic Survey Ozone Bulletin
The ozone hole of 2007 is over. The temperature of the ozone layer is now
highest over Antarctica and cools northwards. It is too warm for polar
stratospheric clouds (PSCs) to exist. Generally across Antarctica, ozone values
are around 300 DU. Values are now slowly dropping towards the normal autumn
normal minimum. In general the circum-polar stratospheric vortex was more
disturbed this year than it was last year, however there were also periods of
stability. Some areas of Antarctica saw ozone values down to ozone hole levels
(less than 220 DU) in mid June, suggesting the possibility of early chemical
depletion, combined with some dynamic processes. In mid July the minimum
temperature of the Antarctic stratosphere at 70 & 50 hPa was close to the
normal, although that at 30 hPa was below the normal, and I suggested the
likelihood of another strong ozone hole year. Early August saw the largest ozone
hole recorded for this time of year, although at the same time very high ozone
levels existed over the northern Antarctic Peninsula. The vortex was more
circular in mid September but returned to an elliptical shape and initially
warmed slowly. In mid September the ozone hole area reached a maximum of just
over 24 million square kilometres, but it then slowly shrank as the vortex
warmed further. A spring warming took place over the Pacific coast of Antarctica
and the Antarctic Peninsula in late October, however this subsided as the ozone
hole became more symmetric again. A second major warming took place towards the
end of November, but subsided in early December. Around December 8 the ozone
hole was briefly the largest on record for the date. The tip of South America
and the Falkland Islands saw ozone levels below 250 DU on August 24, with South
Georgia experiencing similar levels on September 4. The fringes of the ozone
hole were over South Georgia on September 11. The area was intermittently
affected from September 22 to October 22, with South Georgia particularly
affected on September 25, when values dropped below 175 DU. The Falklands and
South Georgia were affected for a final time between November 23 and 25.
Situation at 2007
December 17
British Antarctic Survey Ozone Bulletin
The ozone hole of 2007 is essentially over, although a small weakening polar
vortex remains over East Antarctica. The temperature of the ozone layer
within the vortex is now too warm for PSCs. Ozone values here are still
low, with ozone values below 250 DU and depletions approaching 30%.
Elsewhere over Antarctica ozone values are higher, up to 350 DU in places.
A spring warming took place over the Pacific coast of Antarctica and the
Antarctic Peninsula in late October, however this subsided as the ozone hole
became more symmetric again. A second major warming took place towards the
end of November, but subsided in early December. The summer
circulation is likely to be established by the December solstice. In
general the vortex has been more disturbed this year than it was last year,
however there have also been periods of stability. Early August saw the
largest ozone hole recorded for this time of year, although at the same time
very high ozone levels existed over the northern Antarctic Peninsula. The
vortex was more circular in mid September but returned to an elliptical shape
and initially warmed slowly. In mid September the ozone hole area reached
a maximum of just over 24 million square kilometres, but it then slowly shrank
as the vortex warmed further. Around December 8 the ozone hole was briefly
the largest on record for the date. The vortex is expected to
continue to decline over the next week, but is likely to remain over East
Antarctica until the December solstice. The tip of South America and the
Falkland Islands saw ozone levels below 250 DU on August 24, with South Georgia
experiencing similar levels on September 4. The fringes of the ozone hole
were over South Georgia on September 11. The area was intermittently
affected from September 22 to October 22, with South Georgia particularly
affected on September 25, when values dropped below 175 DU. The Falklands and
South Georgia were affected for a final time between November 23 and 25.
Some areas of Antarctica saw
ozone values down to ozone hole levels (less than 220 DU) in mid June,
suggesting the possibility of early chemical depletion, combined with some
dynamic processes.
In mid July 2007 the minimum
temperature of the Antarctic stratosphere at 70 & 50 hPa was close to the
normal, although that at 30 hPa was below the normal, suggesting the likelihood
of another strong ozone hole year. This prediction has generally held up,
with the ozone hole the largest it has been in early August, and 50% depletion
over some areas of Antarctica.
Situation at 2007
November 30
British Antarctic Survey Ozone Bulletin
The slowly shrinking polar vortex remains in place, with higher ozone values,
approaching 400 DU in places, outside the vortex. The temperature of the ozone
layer within the vortex remains sufficiently cold that a few stratospheric
clouds still exist and some chemical depletion of ozone continues, although
temperatures have risen above the PSC formation threshold. A spring warming took
place over the Pacific coast of Antarctica and the Antarctic Peninsula in late
October, however this subsided as the ozone hole became more symmetric again, a
second major warming took place towards the end of November. Inside the vortex,
ozone values are still below 220 DU, with lowest ozone values are around 200 DU
over East Antarctica. In general the vortex has been more disturbed this year
than it was last year, however there have also been periods of stability.
Early August saw the largest
ozone hole recorded for this time of year, although at the same time very high
ozone levels existed over the northern Antarctic Peninsula. The vortex was more
circular in mid September but returned to an elliptical shape and initially
warmed slowly. In mid September its area reached a maximum of just over 24
million square kilometres, but has now declined to 3 million square kilometres,
close to the average for the last decade at this time of year. The vortex is
expected to continue to decline over the next week.
The tip of South America and
the Falkland Islands saw ozone levels below 250 DU on August 24, with South
Georgia experiencing similar levels on September 4. The fringes of the ozone
hole were over South Georgia on September 11. The area was intermittently
affected from September 22 onwards, with South Georgia particularly affected on
September 25, when values dropped below 175 DU. Some areas of Antarctica saw
ozone values down to ozone hole levels (less than 220 DU) in mid June,
suggesting the possibility of early chemical depletion, combined with some
dynamic processes. In mid July 2007 the minimum temperature of the Antarctic
stratosphere at 70 & 50 hPa was close to the normal, although that at 30 hPa was
below the normal, suggesting the likelihood of another strong ozone hole year.
This prediction has generally held up, with the ozone hole the largest it has
been in early August, and 50% depletion over some areas of Antarctica.
Situation at 2007
November 9
British Antarctic Survey Ozone Bulletin
The shrinking polar vortex remains in place, with higher ozone values,
approaching 400 DU in places, outside the vortex. The temperature of the ozone
layer within the vortex remains sufficiently cold that some stratospheric clouds
still exist and chemical depletion of ozone continues, although temperatures
have risen above the PSC threshold. Over the Pacific coast of Antarctica and the
Antarctic Peninsula a spring warming has taken place, with ozone layer
temperatures too high for stratospheric clouds. Inside the vortex, ozone values
are below 220 DU, with the ozone hole covering about half the continent. Lowest
ozone values are around 150 DU near the centre of Antarctica. In general the
vortex has been more disturbed this year than it was last year. Early August saw
the largest ozone hole recorded for this time of year, although at the same time
very high ozone levels existed over the northern Antarctic Peninsula. The vortex
was more circular in mid September but returned to an elliptical shape and
initially warmed slowly. In mid September its area reached a maximum of just
over 24 million square kilometres, but has since declined to 10 million square
kilometres, close to the average for the last decade at this time of year.
Some areas of Antarctica saw
ozone values down to ozone hole levels (less than 220 DU) in mid June,
suggesting the possibility of early chemical depletion, combined with some
dynamic processes. The tip of South America and the Falkland Islands saw ozone
levels below 250 DU on August 24, with South Georgia experiencing similar levels
on September 4. The fringes of the ozone hole were over South Georgia on
September 11. The area was intermittently affected from September 22 onwards,
with South Georgia particularly affected on September 25, when values dropped
below 175 DU.
In mid July 2007 the minimum
temperature of the Antarctic stratosphere at 70 & 50 hPa was close to the
normal, although that at 30 hPa was below the normal, suggesting the likelihood
of another strong ozone hole year. In late August this prediction seemed to be
holding, with the ozone hole the largest it had been in early August, and 50%
depletion over some areas of Antarctica. Currently it is about average in size
compared to the last decade.
Situation at 2007
October 15
British Antarctic Survey Ozone Bulletin
The winter polar vortex remains in place, with higher ozone values, exceeding
400 DU in places, outside the vortex. The temperature of the ozone layer within
the vortex remains sufficiently cold that stratospheric clouds continue to exist
and chemical depletion of ozone continues. Here, ozone values are below 220 DU,
with the ozone hole covering much of the continent, but offset towards the
Atlantic. Lowest ozone values are below 130 DU over Halley. In general the
vortex is more disturbed this year than it was last year. Early August saw the
largest ozone hole recorded for this time of year, although at the same time
very high ozone levels existed over the northern Antarctic Peninsula. The vortex
was more circular in mid September but has returned to an elliptical shape and
is warming slowly. In mid September its area was 24 million square kilometres,
but has since declined to 16 million square kilometres, only a little smaller
than the average for the last decade at this time of year. Some areas of
Antarctica saw ozone values down to ozone hole levels (less than 220 DU) in mid
June, suggesting the possibility of early chemical depletion, combined with some
dynamic processes. The tip of South America and the Falkland Islands saw ozone
levels below 250 DU on August 24, with South Georgia experiencing similar levels
on September 4. The fringes of the ozone hole were over South Georgia on
September 11. The area was intermittently affected from September 22 onwards,
with South Georgia particularly affected on September 25, when values dropped
below 175 DU.
In mid July 2007 the minimum
temperature of the Antarctic stratosphere at 70 & 50 hPa was close to the
normal, although that at 30 hPa was below the normal, suggesting the likelihood
of another strong ozone hole year. In late August this prediction seemed to be
holding, with the ozone hole the largest it had been in early August, and 50%
depletion over some areas of Antarctica. Currently it is about average in size
compared to the last decade.
Situation at 2007
October 8
British Antarctic Survey Ozone Bulletin
The winter polar vortex remains in place, with higher ozone values, exceeding
400 DU in places, outside the vortex. In general the vortex is more disturbed
this year than it was last year. The temperature of the ozone layer within the
vortex is sufficiently cold that stratospheric clouds have formed and this has
led to rapid chemical depletion of ozone. Inside the vortex, ozone values are
below 220 DU, with the ozone hole covering much of the continent, and offset
towards the Atlantic. Lowest ozone values are below 130 DU in Dronning Maud
Land. Early August saw the largest ozone hole recorded for this time of year,
although at the same time very high ozone levels existed over the northern
Antarctic Peninsula. The vortex was more circular in mid September but has
returned to an elliptical shape and is warming slowly. In mid September its area
was 24 million square kilometres, but has since declined to 19 million square
kilometres, only a little smaller than the average for the last decade at this
time of year. Some areas of Antarctica saw ozone values down to ozone hole
levels (less than 220 DU) in mid June, suggesting the possibility of early
chemical depletion, combined with some dynamic processes. The tip of South
America and the Falkland Islands saw ozone levels below 250 DU on August 24,
with South Georgia experiencing similar levels on September 4. The fringes of
the ozone hole were over South Georgia on September 11. The area was
intermittently affected from September 22 onwards, with South Georgia
particularly affected on September 25, when values dropped below 175 DU. The
edges of the ozone hole are expected to cross South Georgia between October 10
and 12.
In mid July 2007 the minimum
temperature of the Antarctic stratosphere at 70 & 50 hPa was close to the
normal, although that at 30 hPa was below the normal, suggesting the likelihood
of another strong ozone hole year. In late August this prediction seemed to be
holding, with the ozone hole the largest it had been in early August, and 50%
depletion over some areas of Antarctica. Currently it is about average in size
compared to the last decade.
Situation at 2007
October 2
European Space Agency-The ozone hole over Antarctica has shrunk 30 percent
as compared to last year’s record size. According to measurements made by ESA’s
Envisat satellite, this year’s ozone loss peaked at 27.7 million tonnes,
compared to the 2006 record ozone loss of 40 million tonnes. Full story
click here
Situation
at 2007 October 1
British Antarctic Survey Ozone Bulletin The winter polar vortex remains in
place, with higher ozone values, exceeding 500 DU in places, outside the vortex.
In general the vortex is more disturbed this year than it was last year. The
temperature of the ozone layer within the vortex is sufficiently cold that
stratospheric clouds have formed and this has led to rapid chemical depletion of
ozone. Inside the vortex, ozone values are below 220 DU, with the ozone hole
covering much of the continent, and offset towards the Atlantic. Lowest ozone
values are below 125 DU in central Antarctica. Early August saw the largest
ozone hole recorded for this time of year, although at the same time very high
ozone levels existed over the northern Antarctic Peninsula. The vortex was more
circular in mid September but has returned to an elliptical shape and is warming
slowly. In mid September its area was 24 million square kilometres, but has
since declined to 19 million square kilometres, rather smaller than the average
for the last decade at this time of year. Some areas of Antarctica saw ozone
values down to ozone hole levels (less than 220 DU) in mid June, suggesting the
possibility of early chemical depletion, combined with some dynamic processes.
The tip of South America and the Falkland Islands saw ozone levels below 250 DU
on August 24, with South Georgia experiencing similar levels on September 4. The
fringes of the ozone hole were over South Georgia on September 11. The area was
intermittently affected from September 22 onwards, with South Georgia
particularly affected on September 25, when values dropped below 175 DU. The
edges of the ozone hole are expected to remain across the tip of South America,
the Falkland Islands and South Georgia until the end of this week, with
depletion exceeding 30% at times. In mid July 2007 the minimum temperature of
the Antarctic stratosphere at 70 & 50 hPa was close to the normal, although that
at 30 hPa was below the normal, suggesting the likelihood of another strong
ozone hole year. In late August this prediction seemed to be holding, with the
ozone hole the largest it had been in early August, and 50% depletion over some
areas of Antarctica. Currently it is about average in size compared to the last
decade.
Situation
at 2007 September 24
British Antarctic Survey Ozone Bulletin The winter polar vortex is in
place, with higher ozone values, exceeding 500 DU in places, outside the vortex.
In general the vortex is more disturbed this year than it was last year. The
temperature of the ozone layer within the vortex is sufficiently cold that
stratospheric clouds have formed and this has led to rapid chemical depletion of
ozone. Inside the vortex, ozone values are below 220 DU, with the ozone hole
covering much of the continent. Lowest ozone values are below 125 DU in central
Antarctica. Early August saw the largest ozone hole recorded for this time of
year, although at the same time very high ozone levels existed over the northern
Antarctic Peninsula. The vortex was more circular in mid September but is
returning to an elliptical shape and warming slightly. In mid September its area
was 24 million square kilometres, but has since declined to 19 million square
kilometres, rather smaller than the average for the last decade at this time of
year. Some areas of Antarctica saw ozone values down to ozone hole levels (less
than 220 DU) in mid June, suggesting the possibility of early chemical
depletion, combined with some dynamic processes. The tip of South America and
the Falkland Islands saw ozone levels below 250 DU on August 24, with South
Georgia experiencing similar levels on September 4. The fringes of the ozone
hole were over South Georgia on September 11. The hole is expected to extend
across the tip of South America, the Falkland Islands and South Georgia over
September 22 – 25 and strengthen again.
Situation
at 2007 September 14
British Antarctic Survey Ozone Bulletin The winter polar vortex is in
place, with higher ozone values, exceeding 450 DU in places, outside the vortex.
The temperature of the ozone layer within the vortex is sufficiently cold that
stratospheric clouds have formed and this is leading to rapid chemical depletion
of ozone. Inside the vortex, ozone values are below 220 DU, with the ozone hole
covering much of the continent. Lowest ozone values are below 150 DU in the
region of the Weddell Sea. Early August saw the largest ozone hole recorded for
this time of year, although at the same time very high ozone levels existed over
the northern Antarctic Peninsula. The vortex is generally elliptical in shape
but is currently more circular. In early September its area was 21 million
square kilometres, near the average for the last decade. Some areas of
Antarctica saw ozone values down to ozone hole levels (less than 220 DU) in mid
June, suggesting the possibility of early chemical depletion, combined with some
dynamic processes. The tip of South America and the Falkland Islands saw ozone
levels below 250 DU on August 24, with South Georgia experiencing similar levels
on September 4. The fringes of the ozone hole were over South Georgia on
September 11, and are expected over the tip of South America and South Georgia
from September 13 -16.
In mid July 2007 the minimum
temperature of the Antarctic stratosphere at 70 & 50 hPa was close to the
normal, although that at 30 hPa was below the normal, suggesting the likelihood
of another strong ozone hole year. In late August this prediction seemed to be
holding, with the ozone hole the largest it had been in early August, and 50%
depletion over some areas of Antarctica. Currently it is about average in size
compared to the last decade, however it is likely to shrink over the coming
week.
Situation
at 2007 September 7
British Antarctic Survey Ozone Bulletin The winter polar vortex is in
place, with higher ozone values, exceeding 400 DU in places, outside the vortex.
The temperature of the ozone layer within the vortex is sufficiently cold that
stratospheric clouds have formed and this is leading to rapid chemical depletion
of ozone. Inside the vortex, ozone values are below 220 DU, with the ozone hole
covering much of the continent. Lowest ozone values are approaching 150 DU over
the base of the Antarctic Peninsula. Early August saw the largest ozone hole
recorded for this time of year, although at the same time very high ozone levels
existed over the northern Antarctic Peninsula. The vortex is generally
elliptical in shape and is currently orientated roughly parallel to the
Greenwich Meridian. In early September its area was 21 million square
kilometres, near the average for the last decade. Some areas of Antarctica saw
ozone values down to ozone hole levels (less than 220 DU) in mid June,
suggesting the possibility of early chemical depletion, combined with some
dynamic processes. The tip of South America and the Falkland Islands saw ozone
levels below 250 DU on August 24, with South Georgia experiencing similar levels
on September 4. The fringes of the ozone hole are expected to be over South
Georgia on September 11, and over the tip of South America and South Georgia
from September 13 -16.
In mid July 2007 the minimum
temperature of the Antarctic stratosphere at 70 & 50 hPa was close to the
normal, although that at 30 hPa was below the normal, suggesting the likelihood
of another strong ozone hole year. In late August this prediction seemed to be
holding, with the ozone hole the largest it had been in early August, and 50%
depletion over some areas of Antarctica.
Situation
at 2007 August 30
British Antarctic Survey Ozone Bulletin The winter polar vortex is in
place, with higher ozone values, exceeding 400 DU in places, outside the vortex.
The temperature of the ozone layer within the vortex is sufficiently cold that
stratospheric clouds have formed and this is leading to rapid chemical depletion
of ozone. Here, ozone values are below 220 DU, with the ozone hole covering much
of the continent. Ozone values are already below 120 DU over East Antarctica.
Early August saw the largest ozone hole recorded for this time of year, although
at the same time very high ozone levels existed over the northern Antarctic
Peninsula. The vortex is generally elliptical in shape and is forecast to extend
northwards over the tip of South America from August 30 to September 1 and
towards South Georgia over September 4 and 5. In late August its area was 21
million square kilometres, roughly the same as in 2005 and 2006. Some areas of
Antarctica saw ozone values down to ozone hole levels (less than 220 DU) in mid
June, suggesting the possibility of early chemical depletion, combined with some
dynamic processes. The tip of South America and the Falkland Islands saw ozone
levels below 250 DU on August 24.
In mid July 2007 the minimum
temperature of the Antarctic stratosphere at 70 & 50 hPa was close to the
normal, although that at 30 hPa was below the normal, suggesting the likelihood
of another strong ozone hole year. In late August this prediction seemed to be
holding, with the ozone hole the largest it had been in early August, and 50%
depletion over some areas of Antarctica.
WMO Antarctic Ozone
Bulletin 28 August 2007. It
reports that the size and depth of the ozone hole are similar to recent years at
this time. Although it emerged earlier this year, it is still too early to tell
how it will compare with the record large ozone hole of 2006. Ozone depletion
usually continues until early October, so it will be a further five weeks or so
before a clear statement can be made.
Situation
at 2007 August 13
British Antarctic Survey Ozone Bulletin The winter polar vortex is in
place, with higher ozone values, exceeding 400 DU in places, outside the vortex.
The temperature of the ozone layer within the vortex is sufficiently cold that
stratospheric clouds have formed and this is leading to rapid chemical depletion
of ozone. Here, ozone values are below 220 DU, with the ozone hole covering much
of the continent. The vortex is generally elliptical in shape and is forecast to
extend northwards towards South Georgia later this week. Lowest values are
currently over West Antarctica, and this area is forecast to move towards the
Antarctic Peninsula over the next few days. Some areas of Antarctica saw ozone
values down to ozone hole levels (less than 220 DU) in mid June, suggesting the
possibility of early chemical depletion, combined with some dynamic processes.
In mid July 2007 the minimum temperature of the Antarctic stratosphere at 70 &
50 hPa was close to the normal, although that at 30 hPa was below the normal,
suggesting the likelihood of another strong ozone hole year.
Situation
at 2007 August 7
British Antarctic Survey Ozone Bulletin The winter polar vortex is in
place, with higher ozone values, exceeding 500 DU in places, outside the vortex.
Inside the vortex, ozone values are below 220 DU, with the ozone hole covering
much of the continent. The temperature of the ozone layer is sufficiently cold
that stratospheric clouds have formed and this is leading to rapid chemical
depletion of ozone. Some areas of Antarctica saw ozone values down to ozone hole
levels (less than 220 DU) in mid June, suggesting the possibility of early
chemical depletion, combined with some dynamic processes. The vortex is
generally elliptical in shape and is forecast to extend northwards towards the
tip of South America later this week. Currently ozone values are unusually high
over the northern Antarctic Peninsular and Weddell Sea.
In mid July 2007 the minimum
temperature of the Antarctic stratosphere at 70 & 50 hPa was close to the
normal, although that at 30 hPa was below the normal, suggesting the likelihood
of another strong ozone hole year.
Situation
at 2007 July 25British
Antarctic Survey Ozone Bulletin The winter polar vortex
is in place, with higher ozone values, exceeding 400 DU in places, outside the
vortex. Inside the vortex, ozone values are around 250 DU. The
temperature of the ozone layer is sufficiently cold that stratospheric clouds
have formed. Some areas of Antarctica saw ozone values down to ozone
hole levels (less than 220 DU) in mid June, suggesting the possibility of early
chemical depletion, combined with some dynamic processes.
In mid July 2007 the minimum temperature
of the Antarctic stratosphere at 70 & 50 hPa was close to the normal, although
that at 30 hPa was below the normal, suggesting the likelihood of another strong
ozone hole year.
27 June
2007
British Antarctic Survey Ozone Bulletin The winter polar vortex
is beginning to build, and higher ozone values, approaching 400 DU in places,
are seen outside the vortex. The temperature of the ozone layer is sufficiently
cold for stratospheric clouds to form. Some areas of Antarctica have already
seen ozone values down to ozone hole levels (less than 220 DU), suggesting the
possibility of early chemical depletion, combined with some dynamic processes.
In early June 2007 the minimum temperature of the Antarctic stratosphere was
close to the normal, suggesting the likelihood of an average ozone hole year.
4 June 2007
British Antarctic Survey Ozone Bulletin
A significant part of the Antarctic stratosphere is now below the temperature at
which stratospheric clouds can form.
3 May 2007
British Antarctic Survey Ozone Bulletin The winter polar vortex
is beginning to build, and higher ozone values are seen outside the vortex. The
temperature of the ozone layer is declining from the summer high and
temperatures in the ozone layer are now close to the mean of the last few
decades, having generally been below the mean from March 2006 until March 2007.
The temperature is above the value at which stratospheric clouds can form. Ozone
values are however approaching 230 DU in the Pacific sector of Antarctica, with
depletions of over 30%.
