Situation
at 2005 December 19 British Antarctic Survey
Ozone BulletinStratospheric
temperatures rose rapidly in November and the 2005 ozone hole is over.
Generally ozone levels are at their summer maximum. There is, however,
still a small area over the south pole with ozone levels below 250 DU,
which is over 30% down on the normal for the time of year. The 2005 ozone
hole was one of the deepest and largest recorded, with a peak of 25
million square kilometres in early September. Ozone values at Rothera in
September were among the lowest recorded at this time of year, and values
around 110 DU were reached on September 11, 19 and 20. Both Halley and
Vernadsky recorded their second lowest values ever during September. The
tip of South America and the Falkland Islands were affected by the edges
of the ozone hole between August 30 and September 2; September 10 and 12;
September 16 and 18; September 25 and 27. During these periods values
dropped to over 20% below the normal for the time of year, and in the end
of September event were over 30% down, with values below 200 DU. The
region was affected by severe ozone depletion from October 7 to 10, when
ozone amounts dropped 50% below the normal levels. South Georgia
experienced low ozone values from October 9 to October 22. The Arctic
ozone layer is in its winter state and temperatures near the top of the
ozone layer are cold enough for stratospheric clouds to form. Ozone
amounts over most of the Northern Hemisphere are generally between 250 and
400 DU. Stratospheric temperatures over the north Atlantic are below
-75°C and ozone values over the northern UK are below 250 DU, which is
approaching 30% below the normal for this time of year. Chemical ozone
depletion is likely to be taking place. Elsewhere ozone values are
generally not far from the normal.
Situation at 2005
October 28-The
2005 ozone hole was one of the deepest and largest recorded. The
atmospheric circulation over the Antarctic continent is now emerging from
its winter state. Stratospheric temperatures are however still cold enough
for stratospheric clouds to exist, although temperatures are rising.
Stratospheric clouds have been observed at Rothera and Vernadsky. There is
still widespread ozone depletion over the continent, with ozone amounts
over 50% down on the normal for the time of year in many places. Lowest
ozone amounts are below 150 DU, though the ozone hole is beginning to
fill. The lowest ozone areas are over the Elsworth Mountains. Overall the
area of the ozone hole is around 13 million square kilometres. It is now
significantly smaller than its peak of 25 million square kilometres in
early September. Ozone values at Rothera in September were among the
lowest recorded at this time of year, and values around 110 DU were
reached on September 11, 19 and 20. The tip of South America and the
Falkland Islands were affected by the edges of the ozone hole between
August 30 and September 2; September 10 and 12; September 16 and 18;
September 25 and 27. During these periods values dropped to over 20% below
the normal for the time of year, and most recently have been over 30%
down, with values below 200 DU. The region was affected by severe ozone
depletion from October 7 to 10, when ozone amounts dropped 50% below the
normal levels. South Georgia experienced low ozone values from October 9
to October 22. Temperatures in the Arctic stratosphere were cold enough
for stratospheric clouds to form until mid March. Very low ozone levels
(230 DU) were recorded over the UK from March 18 to 21. A rapid spring
warming then took place and it is now too warm for such clouds to exist in
the Arctic stratosphere. Ozone amounts over most of the Northern
Hemisphere are generally between 220 and 350 DU. Parts of Siberia are 20%
below the normal, but elsewhere they are generally 5 - 15% below the
normal. Values over the UK are around 300 DU, which is a little above the
normal for this time of year. Generally ozone amounts are declining
towards the normal autumn minimum.
October
18 2005This year's
seasonal ozone hole over Antarctica was the third largest on record, but
forecasters are uncertain how it will behave in the future, the World
Meteorological Organisation (WMO) said Tuesday.
October
13 2005 World
Meteorological Organization-
No 5/2005
Executive summary Since the last WMO Antarctic Ozone Bulletin 14 days ago,
the area where temperatures are below the threshold for formation of PSCs
of type I (nitric acid trihydrate, NAT) has continued to decrease and is
now close to zero. This area has been close to the 2003 values and well
above the 1995-2004 average throughout the month of September and the
first week of October. The area where the total ozone column is less than
220 DU is now on the way down after reaching its maximum around 20
September. Although the ozone hole area has remained nearly constant
during the last two weeks, it is now being filled up with ozone, and
minimum values, as seen by satellites, are now around 125 DU, after being
down to 106 DU on 30 September. Ground-based observations from Belgrano
showed a total ozone column of 94 DU on 4 October, which is the lowest
ever measured at that station. The maximum observed UV index at Antarctic
stations has increased since the previous Bulletin from 4.4 to 6. At
Ushuaia, Argentina, the UV index reached 8 on 8 October, which is
unusually high for this time of the year.
Situation at 2005
October 6-British Antarctic Survey
Ozone Bulletin
The 2005 ozone
hole is one of the deepest and largest recorded. The atmospheric
circulation over the Antarctic continent is emerging from its winter
state. Stratospheric temperatures have been cold enough for stratospheric
clouds to form, and although temperatures are rising they are still
widespread. Stratospheric clouds have been observed at Rothera and
Vernadsky. There is widespread ozone depletion over the continent, with
ozone amounts over 50% down on the normal for the time of year in many
places. Lowest ozone amounts are below 100 DU, with all areas of the edge
region below 200 DU, though amounts are beginning to rise. The lowest
ozone areas are near Halley. Overall the area of the ozone hole is around
22 million square kilometres but is a little smaller in size than the 2003
hole, which was one of the largest on record. It is a little smaller than
its peak of 25 million square kilometres in early September. Ozone values
at Rothera in September were among the lowest recorded at this time of
year, and values around 110 DU were reached on September 11, 19 and 20.
The tip of South America and the Falkland Islands were affected by the
edges of the ozone hole between August 30 and September 2; September 10
and 12; September 16 and 18; September 25 and 27. During these periods
values dropped to over 20% below the normal for the time of year, and most
recently have been over 30% down, with values below 200 DU. The region is
likely to be affected by severe ozone depletion from October 8 to 10, when
ozone amounts may drop 50% below the normal levels. South Georgia is
likely to experience low ozone values until October 13.
Situation at 2005
September 23-British Antarctic Survey
Ozone Bulletin
The
atmospheric circulation over the Antarctic continent is in its winter
state. Stratospheric temperatures are cold enough for stratospheric clouds
to form and they have been observed at Rothera and Vernadsky. There is
widespread ozone depletion over the continent, with ozone amounts over 50%
down on the normal for the time of year in places. Lowest ozone amounts
are approaching 100 DU, with most areas of the edge region below 200 DU.
The lowest ozone areas are over the base of the Antarctic Peninsula and
the Weddell Sea. Overall the area of the ozone hole is around 22 million
square kilometres but is a little smaller in size than the 2003 hole,
which was one of the largest on record during August. Ozone values at
Rothera are amongst the lowest recorded at this time of year. The tip of
South America and the Falkland Islands was affected by the very edge of
the ozone hole for a few days at the end of August and beginning of
September, when values dropped to over 20% below the normal for the time
of year.The tip of South America was again affected by the edge of the
hole from September 10 to 13. The area is likely to be affected
again around September 22 - 25
30
August 2005 European
Space Agency-This season's Antarctic ozone hole has swollen to
an
area of ten million square kilometres from mid-August - approximately the same
size as Europe
and
still expanding. It is expected to reach maximum extent during September, and
ESA satellites
are
vital for monitoring its development.
This
year's hole is large for this time of year, based on results from the last
decade: only the ozone
holes
of 1996 and 2000 had a larger area at this point in their development. Envisat's
Scanning
Imaging
Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) routinely
monitors
ozone
levels on a global basis, continuing a dataset of measurements stretching back
to mid-1995, previously made by the Global Ozone Monitoring Experiment (GOME)
aboard the earlier ESA
spacecraft
ERS-2.
ESA
data form the basis of an operational near-real time ozone monitoring and
forecasting service forming part of the PROMOTE (PROtocol MOniToring for the
GMES Service Element) consortium,
made
up of more than 30 partners from 11 countries, including the Royal Dutch
Meteorological Institute (KNMI).As
part of the PROMOTE service, the satellite results are combined with
meteorological data and wind field models so that robust ozone and ultraviolet
forecasts can be made. In a first for ESA, these results
are being used by the World Meteorological Organisation (WMO) to compile their
regularly-updated Antarctic Ozone Bulletin.The precise time and range of Antarctic ozone hole occurrences are determined by
regional meteorological variations. During the southern hemisphere winter, the
atmospheric mass above the Antarctic continent is kept cut off from exchanges
with mid-latitude air by prevailing winds known as the polar vortex. This leads
to very low temperatures, and in the cold and continuous darkness of this season,
polar stratospheric clouds are formed that contain chlorine.
The
stratospheric ozone layer that protects life on Earth from harmful ultraviolet
(UV) radiation is
vulnerable
to the presence of certain chemicals in the atmosphere such as chlorine,
originating from man-made pollutants like chlorofluorocarbons (CFCs).
Now
banned under the Montreal Protocol, CFCs were once widely used in aerosol cans
and
refrigerators.
CFCs themselves are inert, but ultraviolet radiation high in the atmosphere
breaks them down into their constituent parts, which can be highly reactive with
ozone.
As
the polar spring arrives, the combination of returning sunlight and the presence
of polar stratospheric clouds leads to splitting of chlorine into highly
ozone-reactive radicals that break ozone down into individual
oxygen molecules. A single molecule of chlorine has the potential to break down
thousands of
molecules of ozone.
The PROMOTE atmospheric ozone forecast seen here has atmospheric ozone
measured in Dobson Units (DUs), which stands for the total thickness of ozone in
a given vertical column if it were
concentrated
into a single slab at standard temperature and atmospheric pressure – 400 DUs
is equivalent to a thickness of four millimetres, for example.
Developing
out of the successful precursor Tropospheric Emission Monitoring Information
Service (TEMIS), PROMOTE is a portfolio of information services covering the
atmosphere part of the Earth System, operating as part of ESA's initial Services
Element of Global Monitoring for Environment and Security (GMES). This is a
joint initiative between ESA and the European Commission to combine all
available ground- and space-based information sources and develop a global
environmental monitoring capability for Europe.
August 22 2005 World
Meteorological Organization-
From May to
mid-August the meteorological conditions in the Antarctic stratosphere were
close to the 1995-2004 average, colder than 2004, but a little warmer than in
2003.The total ozone column along the edge of the Antarctic air mass (vortex) is
significantly smaller than at the same time in 2004 and also somewhat smaller
than in 2003, when the largest ozone hole on record occurred. It is still too
early in the season to give a reliable statement about the size and depth of
this year's Antarctic ozone hole. WMO, in collaboration with the ozone science
community, is using ozone observations and meteorological data to keep a close
eye on the development during the coming weeks and months.
Most
of Antarctica still remains under winter darkness, so the average rate of ozone
loss there remains relatively low. However, total ozone column maps synthesised
by the World Ozone and UV Data Centre at
Environment Canada, using surface-based WMO/GAW network observations and
satellite data, show that
the sunlit parts of the vortex in mid-August have total ozone column values well
below 200 DU and even
close to 150 DU along the vortex edge, and in particular in the regions around
the Antarctic Peninsula.
This
is considerably lower than at the same time in 2004 when the lowest ozone column
was around
240 DU and also somewhat lower than in mid-August 2003. This result
has been confirmed by independent analyses and forecasts carried out by the
Royal Netherlands Meteorological Institute
Temperatures
are still sufficiently low within the polar vortex to maintain the chemical
processes
required for the formation of the annually recurring Antarctic ozone
hole The ozone hole usually
does not reach its maximum size until mid- to late
September, but already by mid-August, one
can see the first signs of ozone
destruction. As the sun rises over Antarctica during the coming
weeks, the ozone
hole is expected to deepen. The amount of ozone loss will be dependent upon
prevailing meteorological conditions in the stratosphere, particularly during
September and October. This situation is expectedto continue as long as the
stratosphere contains an excess of ozone depleting substances. In August, ozone
loss is limited and the sun is still low in the sky, so the intensity of
ultraviolet (UV) radiation in areas usually affected by the ozone hole is
modest. UV levels will be reported in future ozone bulletins.
Situation at 2005 June 20-British Antarctic Survey
Ozone Bulletin
The atmospheric circulation over
the Antarctic continent is in its early winter state. The ozone layer over
much of the Southern Hemisphere south of 50° is 10 - 15% below the long term
normal. Ozone values are below 230 DU over parts of Antarctica.
Stratospheric temperatures are now cold enough for stratospheric clouds to begin
forming.
Information about the 2004 ozone
hole is in the archive
report for 2004/5.
Temperatures in the Arctic
stratosphere were cold enough for stratospheric clouds to form until mid March.
A rapid spring warming then took place and it is now too warm for such clouds to
exist in the Arctic stratosphere. Ozone amounts over parts of the Northern
Hemisphere are over 15% below the normal, but all areas have ozone levels
above 300 DU. Although values over the UK are around 300 DU, this is 10%
below the normal for this time of year, hence there is a high risk of sun-burn.
Values are expected to remain below normal for the next few days. Very low ozone
levels (230 DU) were recorded over the UK from March 18 to 21.
Note: The Antarctic
ozone hole is usually largest in early September and deepest in late September
to early October. September 16 is world ozone day. Prior to the
formation of ozone holes, Antarctic ozone values were normally at their lowest
in the autumn (ie March).
Halley - Total ozone:
The 2005 observing season will start in late August. This figure
[updated 2005 April 20] shows the variation in 2004 - 2005 and the normal for
1957-72.
Rothera - Total ozone: Mean values in
2005 fell slowly from 285 DU at the beginning of the year to 260 DU at the
winter solstice, with long period variation of around 20 DU from the mean,
and shorter period variation of 30 DU. This figure
[updated 2005 June 28] shows the variation during the year.
Vernadsky - Total ozone: The 2005 observing season will
start in July. This figure
[updated 2005 June 10] shows the variation in 2004 - 2005 and the normal for
1957-72.
Temperature and PSCs:
The 100 hPa pressure level is near the base of the ozone layer, but is reached
by most radiosonde flights. The temperature at this height
becomes sufficiently cold that polar stratospheric clouds (PSCs) can exist
widely during the winter.
Halley - 100 hPa temperature: The temperature is at winter
values of -80°C. This figure
[updated 2005 April 20] shows the variation at Halley in 2004 - 2005 and the
normal for 1957-72.
Peninsula - 100 hPa temperature: Since the beginning of January
the 100 hPa temperature has been close to the long term normal. This figure
[updated 2005 June 10] (compiled from flights from Marambio, Rothera and the
Polarstern) shows the variation in 2004 - 2005 and the normal for 1957-72.
There has been a radiosonde programme of several flights per week at Rothera
since 2003 March, increasing to daily flights for the QUOBI project from mid
June to mid October 2003. Strong winds on 2004 October 2 & 3
damaged the hangar at Rothera and this has significantly restricted the
conditions under which sondes can be launched. The Polarstern was
stationed in the western Weddell Sea from early December 2004 to early January
2005 and launched one or two sondes each day.
Satellite: Satellite
imagery gives a global perspective on the ozone hole. TOVS (which can image
during the polar night) and TOMS currently have significantly different
calibrations, with TOVS showing lower readings than TOMS. TOMS values are
close to ground-based values. Different satellite operators use slightly
different criteria for defining the area of the ozone hole and hence give
slightly different areas. Our 2004/2005
Antarctic ozone hole movie [updated 2005 June 28] is produced from TOMS images.
The NCEP and KNMI analyses shown on the Canadian
Met Service daily ozone maps pages give a good analysis in the Southern
Hemisphere but the NCEP forecasts tend to increase ozone amounts within the
ozone hole. US NWS CPC
plots from NOAA show the current
area of the ozone hole.
Arctic: Ozone
values over the Arctic since June are shown in our Northern
Hemisphere TOMS movie. Ozone values declined from the spring maximum
in northern temperate and polar regions reaching the normal autumn minimum in
early October. The lowest ever UK reading from Lerwick was recorded on
2004 October 31. Ozone values dropped below 200 DU over parts of the
Arctic in early December. Winter temperatures in the stratosphere were
significantly colder than normal allowing extensive formation of stratospheric
clouds. This led to substantial ozone depletion, at times over 40%.
Very low ozone values, around 230 DU, were recorded over the UK between March 18
and 21. Ozone values over the northern hemisphere are now at summer levels
between 300 and 420 DU. For more UK information see the DEFRA UK
Stratospheric Ozone Measurements page.
Reports of a substantial Arctic
ozone hole forming in response to a solar proton event in the spring of 2004 are
somewhat exaggerated. Although this did lead to substantial depletion of
up to 60% near the top of the ozone layer, less than 10% of the total ozone
column is in this region. The event therefore had less effect than normal
day to day changes and no ozone hole was formed. The spring of 2005 by
contrast had much lower stratospheric temperatures and significant chemical
ozone depletion did take place. Although the column ozone never quite
dropped to "ozone hole" levels, the amount of ozone affected by
chemical depletion is broadly comparable to that seen in the Antarctic ozone
hole.
Equator: Ozone
levels are normally lowest over the topics and TOMS data shows nothing unusual.
TOVS data has a calibration problem and shows values that are significantly
lower than those that are measured by other means.
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