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Ozone Hole 2004
Ozone Hole Area
|
Minimum Ozone
|
|
(million
km2) |
(DU) |
|
Maximum
Daily |
Minimum
Daily |
| Year |
Date |
Value |
Date |
Value |
| 2004 |
22
September |
22.8 |
04
October |
102 |
http://ozonewatch.gsfc.nasa.gov
http://www.cpc.ncep.noaa.gov/products/stratosphere/sbuv2to/ozone_hole.html
2004
Antarctic Ozone Hole
10.12.04 NASA
A relatively warm Antarctic winter in 2004 kept the thinning of the protective
ozone layer over Antarctica, known as the ozone 'hole,' slightly smaller than in
2003. Each year the 'hole' expands over Antarctica, sometimes reaching populated
areas of South America and exposing them to ultraviolet rays normally absorbed
by ozone. Scientists have new tools to study this annual phenomenon, and the
human-produced compounds that contribute to ozone breakdown are decreasing.
Antarctic ozone hole – smaller this
year
1 October 2004
The ozone hole over Antarctica
appears to be about 20% smaller than last year’s record-breaking ozone hole.
Measurements by NIWA, supported
by Antarctica New Zealand, at Scott Base, Antarctica, are consistent with NASA
satellite data showing the area of the hole peaked at about 24 million square
kilometres, compared to 29 million square kilometres in 2003.
“Measurements from the ground
at Scott Base suggest that there is slightly more ozone this year than the
average for recent years,” says NIWA atmospheric scientist Dr Stephen Wood.
“But ozone levels are still lower than before the ozone hole started forming
in the early 1980s.”
“The first spring measurements
of ozone from Scott Base this year showed levels at around 200 Dobson Units (DU)
but have been as low as 165 DU in the past week. Satellite measurements are
reporting values as low as 110 DU in some parts of the hole. Before the early
1980s, ozone levels in Antarctica never went below 220 DU.”
The ozone hole is the result of a
combination of factors: man-made chemicals containing chlorine and bromine; the
isolation and cold of the Antarctic atmosphere during the polar winter; the
formation of polar stratospheric clouds; the chemical reactions that occur on
the surfaces of those clouds; and the return of sunlight in spring.
Although the man-made chemicals
that contribute to ozone depletion are already starting to decline in the
atmosphere (thanks to controls on their use under the Montreal Protocol), some
of the other factors vary from year to year. Because of this natural variation,
Dr Wood cautions against reading too much into the smaller size of the hole this
year. “We need to see smaller or less severe ozone holes over a number of
years before we can say for certain that ozone is recovering,” he says.
At present, the ozone-depleted
air is well contained over Antarctica. The only inhabited area it could affect
at the moment is the extreme tip of South America.
But Dr Wood says the hole will
indirectly affect New Zealand later in the year. “When the ozone hole breaks
up in November or early December, ozone-depleted air moves into surrounding
areas in the southern hemisphere, including New Zealand. The later the ozone
hole breaks up, the higher the sun is in the sky over New Zealand and the larger
the effect on UV levels. If New Zealand experiences a combination of lower ozone
with high sun and few clouds, then skin-damaging UV levels can be extreme.”
Research conducted at NIWA’s
atmospheric research facility at Lauder, Central Otago, shows that approximately
half the long-term ozone decline at mid-latitudes in the southern hemisphere
(including New Zealand) has been caused by the export of ozone-depleted air from
Antarctica. In recent years, there has been about ten percent less ozone over
New Zealand in the summer than 30 years ago.
NIWA’s measurements of ozone
near Scott Base are part of research funded by the Foundation for Research
Science and Technology to understand what drives global change in the
atmosphere. The ground-based measurements are also important for validating
measurements taken from satellites.
The ozone layer over Antarctica is in the
normal winter circulation pattern, however ozone depletion has begun at the edge
of the circumpolar vortex. Ozone values are generally slightly higher around
Antarctica, with lower values over the continent. Some areas are already below
200 DU (a frequent measure of ozone hole conditions) with depletions of above
35%. So far, the area over Antarctica with conditions suitable for ozone
depletion is smaller than in 2003.
2004 September 1
Envisat
witnesses return of the South Polar ozone hole
The ozone hole (where ozone
values are below 220 DU) has grown rapidly over the last fortnight and now
covers nearly 15 million square kilometres. The lowest ozone values are
over the Weddell Sea and here values are 40% below normal. Ozone values
are higher in a broad band between 60°S and 30°S, in places exceeding 400 DU.
Situation at 2004 September 6-British Antarctic Survey
Ozone Bulletin
The ozone hole (where ozone
values are below 220 DU) has grown rapidly over the last fortnight and now
covers nearly 18 million square kilometres, about average over the last decade.
The lowest ozone values are over the Weddell Sea and here values are 40% below
normal. Ozone values are higher in a broad band between 60°S and 30°S, in
places exceeding 400 DU. The edges of the ozone hole are expected to pass over
the southern tip of South America, the Falkland Islands and South Georgia from
September 10 to 12.
The ozone hole (where ozone
values are below 220 DU) grew rapidly from mid August to early September
and covers around 18 million square kilometres, about average over the last
decade. It has remained at a similar size for the last ten days. The
lowest ozone values are over the southern Weddell Sea and Ronne Ice Shelf, and
here values are nearly 50% below normal. Ozone values are higher in a
broad band between 60°S and 30°S, in places exceeding 400 DU. The edge
of the ozone hole passed over the southern tip of South America, the Falkland
Islands and South Georgia from September 10 to 12. It is expected to do so
again from September 19 to 22, with larger ozone depletion possible from
September 21 to 22.
Situation at 2004 September 21-British Antarctic Survey
Ozone Bulletin
The ozone hole (where ozone
values are below 220 DU) grew rapidly from mid August to early September and
covers around 20 million square kilometres, about average over the last decade.
It has only increased a little in area over the last fortnight. The lowest ozone
values are over the southern Antarctic Peninsula and off Enderby Land, and here
values are over 40% below normal. Ozone values are higher in a broad band
between 60°S and 30°S, in places exceeding 400 DU. The edge of the ozone hole
passed over the southern tip of South America, the Falkland Islands and South
Georgia from September 10 to 12. It is expected to do so again from September 19
to 24, with larger ozone depletion possible from September 21 to 23, possibly
affecting regions as far north as 40°S. Note: The ozone hole is usually largest
in early September and deepest in late September to early October. September 16
was world ozone day. Prior to the formation of ozone holes, ozone values were
normally at their lowest in the autumn (ie March).
September 22-
Ozone Hole Reaches South America
The edge of the ozone hole is over the southern tip of South America, the Falkland Islands and South
Georgia
Situation at 2004
October1-British Antarctic Survey
Ozone Bulletin
The ozone
hole (where ozone values are below 220 DU) grew rapidly from mid August to early
September to reach around 19 million square kilometres. It has remained at a
roughly similar area for most of September, which is a little below the average
over the last decade. The lowest ozone values are over the southern Weddell Sea,
and here values are around 50% below normal. Ozone values are higher in a broad
band between 60°S and 30°S, in places over 400 DU. The edge of the ozone hole
passed over the southern tip of South America, the Falkland Islands and South
Georgia from September 10 to 12. It did so again between September 18 and
October 2, with ozone hole levels over southern South America and the Falkland
Islands on September 21 and 22. Ozone values remain low over South Georgia and
are likely to remain so until October 3. Ozone values are again likely to be low
over southern South America, the Falkland Islands and South Georgia between
October 5 and 7, when there are signs of a stratospheric spring warming on the
opposite side of the continent.
Situation at 2004
October 1 and outlook to October 15
British Antarctic Survey
Ozone Bulletin
The ozone hole
(where ozone values are below 220 DU) grew rapidly from mid August to early
September to reach around 19 million square kilometres. It has remained at a
roughly similar area for most of September, which is a little below the average
over the last decade. The lowest ozone values are over the southern Weddell Sea,
and here values are around 50% below normal. Ozone values are higher in a broad
band between 60°S and 30°S, in places over 400 DU. The edge of the ozone hole
passed over the southern tip of South America, the Falkland Islands and South
Georgia from September 10 to 12. It did so again between September 18 and
October 2, with ozone hole levels over southern South America and the Falkland
Islands on September 21 and 22. Ozone values are again likely to be low over
southern South America, the Falkland Islands and South Georgia between October
11 and 15, when there are signs of a stratospheric spring warming on the
opposite side of the continent.
Situation at 2004
November 16-British Antarctic Survey
Ozone Bulletin
The ozone hole
(where ozone values are below 220 DU) grew rapidly from mid August to early
September to reach around 19 million square kilometres. It slowly decreased in
area from a maximum of 20 million square kilometres in mid September to 15
million square kilometres in early October. A major spring warming commenced in
mid October, when the area declined rather more rapidly to 6 million square
kilometres. However, the warming subsided and the area affected slowly declined
from around 10 million square kilometres in late October to around 8 million
square kilometres in mid November. The area of the hole has generally been a
little below the average size of the last decade. Currently, the lowest ozone
values, below 170 DU, are over West Antarctica, and in some places values are
around 50% below normal. Ozone values are higher in a broad band between 60°S
and 30°S, in places above 370 DU. The edge of the ozone hole passed over the
southern tip of South America, the Falkland Islands and South Georgia from
September 10 to 12. It did so again from September 18 to October 2, and October
11 to 15, with ozone hole levels over southern South America and the Falkland
Islands on September 21 and 22. Values were also low over South Georgia on
October 7 and 8. Current stratospheric analyses and forecasts suggest that the
final warming has commenced, with ozone values and temperatures generally
rising, although it is likely that a remnant of the ozone hole will persist of
another week.
Situation at 2004
December 13-British Antarctic Survey
Ozone Bulletin
The 2004 Antarctic ozone hole
season is now over, with the circulation over the continent in its summer mode.
The ozone layer over much of the Southern Hemisphere south of 50° remains
around 10% below the long term normal.
The ozone hole (where ozone
values are below 220 DU) grew rapidly from mid August to early September to
reach around 19 million square kilometres. It slowly decreased in area from a
maximum of 20 million square kilometres in mid September to 15 million square
kilometres in early October. A major spring warming commenced in mid October,
when the area declined rather more rapidly to 6 million square kilometres.
However, the warming subsided and the area affected slowly declined from around
10 million square kilometres in late October to around 8 million square
kilometres in mid November. The ozone hole area rapidly dropped to zero after
mid November. The area of the hole was generally a little below the average size
of the last decade. The edge of the ozone hole passed over the southern tip of
South America, the Falkland Islands and South Georgia from September 10 to 12.
It did so again from September 18 to October 2, and October 11 to 15, with ozone
hole levels over southern South America and the Falkland Islands on September 21
and 22. Values were also low over South Georgia on October 7 and 8.
In the Northern Hemisphere there
is currently significant ozone depletion over the Arctic Ocean.
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