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ANTARCTIC OZONE
This page gives information about ozone at Halley, Rothera and Vernadsky/Faraday stations and was last updated on 2005 June 28.
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.
The 2004 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.
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 observing season
started in late August and finished in mid April. Routine ozone observations prior to late September are of low accuracy due to the low solar
elevation, however the initial observations suggest ozone values fell rapidly from
around 260 DU (15% depletion) in late August to 160 DU in mid September and
thereafter more slowly to reach 145 DU (50% depletion) by the end of the month.
The lowest value recorded this year was 133 DU on October 6. Wave activity
during the spring and early summer was strong, with major ozone peaks in
the second half of October (250 DU - 20% depletion), mid November (270 DU - 30% depletion)
and mid December (290 DU - 20% depletion). Troughs occurred in early
November (180 DU - 50%
depletion), late November (230 DU - 40% depletion) and mid December
(260 DU - 30% depletion). Ozone values peaked at 300 DU (10% depletion) in
late December and fell towards the autumn minimum in early April at around
240 DU (20% depletion). This figure
[updated 2005 April 20] shows the variation in 2004 - 2005 and the normal for 1957-72.
Rothera - Total ozone: Mean values in 2004 fell slowly from 290 DU
at the beginning of the year to 270 DU at the autumn equinox and had risen to
around 300 DU by the end of July. During
August they began to fall and had reached around 150 DU by late September in one of the smoothest
declines to minimum that we have seen at Rothera. The
lowest value recorded after the winter solstice was 136 DU on October 12. A short lived rise to 270
DU in early October was followed by a rapid rise to 340 DU by the end of the
month. Mean values dropped rapidly in early November, briefly declining below 200 DU,
but then slowly rose from around 270 DU, to reach 290 DU at the end
of the year. During the first five months of 2005 mean values have varied
between 250 and 300 DU. This figure shows the variation in
2004, and this figure [updated 2005 June 28] shows the variation in
2005.
Vernadsky - Total ozone: Preliminary observations
suggest that ozone values generally fell from around 280 DU at the beginning of August
(15% depletion) to
around 170 DU by the late September (50% depletion). Values then rose,
briefly peaking at over 300 DU in early October, before dropping to 160 DU around
October 10. Another rapid rise then commenced, reaching normal levels
around 350 DU after mid month. Following this peak, values have generally
varied around 300 DU, with minima below 280 DU (25% depletion) in early November and early
December and a maximum above 320 DU in mid November. They generally dropped from
300 DU at the beginning of 2005 to reach 270 DU (10% depletion) in mid March.
After the equinox they remained around 280 DU, with both short and longer period
variation. The
lowest value recorded following the winter solstice was 154 DU on September 22.
This figure [updated 2005 June 10]
shows the variation in 2004 - 2005 and the normal for 1957-72. Observations
with Dobson 31 ceased at Vernadsky on 2005 March 29 and observations with Dobson
123 commenced on 2005 March 27.
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,
although the area affected this year was at the lower bound of the variation over the last
decade. Rothera reported sightings of nacreous clouds on June 10, July 14, 26,
27, August 2, 3, 6 and September 10. Vernadsky
reported nacreous clouds on June 10, July 14, 18, August 17, 19, 21, 22, 26 and
September 10.
Halley - 100 hPa temperature: The temperature remained at the mean winter value of
-83°C until early September. By mid October it had risen to -76°C, which
was four degrees below the normal. Wave activity during the spring and early
summer was strong. An early and rapid spring warming saw the temperature
rise to -60°C in late October, which is some 8° above the normal.
Further peaks occurred in in mid November (-58°C), early December
(-46°C), late December (-42°C) and late January (-42°C). Troughs occurred in early
November (-70°C , some 10° below the normal), late November (-63°C, 19°
below the normal), mid December (-52°C, 9° below the normal) and mid January
(-44°C, 4° below the normal).
The temperature is declining from the summer maximum, and has reached -58°C,
close to the
normal. This figure [updated
2005 April 20] shows
the variation at Halley in 2004 - 2005 and the normal for 1957-72.
Peninsula - 100 hPa temperature: The 100 hPa temperature
generally declined from -74°C at the beginning of August to -78°C at the end
of September. It then rose, with maxima in late October (-55°C), late
November (-52°C), early December (-48°C) and late December (-46°C). Apart
from the second half of October the temperature was below the long term
normal. Since the beginning of January it 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 10] 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.
The BAS ozone bulletins contained the actual ozone values reported together with an analysis of the situation. These were distributed by email on request, but are now superceded by this web site. The last ozone bulletin was issued on 2002 May 28. The final situation report of each season is archived for historical reference.
Some data is available on line, however please note that this is provisional and likely to change without warning. To help interpret the data you should to read this description. You must request permission to reproduce the data and I may be able to supply more suitable or more up to date material.
Provisional daily mean ozone values for 2004/2005 for
Halley [Updated 2005 April 20] and Vernadsky. [Updated 2005 June 7] The data sets commence on
August 1. The instrument constants for Halley were last adjusted on 2003
October 23. Observations with Dobson 31 ceased at Vernadsky on 2005 March
29 and observations with Dobson 123 commenced on 2005 March 27; during the
overlap period a mean of both instruments is given. Ozone values from
Dobson 123 are likely to undergo frequent revision until the instrument
constants are well determined.
Provisional daily mean ozone values for Faraday/Vernadsky and Halley between 1972 and 2004.
[Updated 2005 June 10]
Provisional monthly mean ozone values for Faraday/Vernadsky and Halley between 1956 and 2004.
Mean daily ozone values for the period 1957 - 1972 for
Faraday and Halley
.
Daily ozone values for the period 1957 - 1973 for Faraday and Halley .
Temperature and Ozone graphs for Halley and Vernadsky/Faraday. [Updated 2005 January 13]
Stratospheric Temperature - Radiosondes are released daily at Halley
and every other day at Rothera. The 100 hPa or 70
hPa pressure level is close to the height of the maximum ozone
concentration. Over the last 30 years the mean 100 hPa
temperature has declined in most months. The most notable change
is in November at Halley.
Monthly 100 hPa temperature means for Bellingshausen/Faraday/Rothera/Marambio/Polarstern and
Halley between 1954 and 2004.
[Updated 2005 June 10]
Rothera - Ozonesondes: During 2003 we carried out ozone sonde flights at Rothera as part of the QUOBI project. Data from these flights is available in NASA-AMES format. Animation of the ozonesonde flight results [note that although the ozone scale on these graphs reads nanobars, it should read mPa].
Rothera - Ozone: The SAOZ instrument at Rothera has measured total column
nitrogen dioxide and ozone since 1997. The values given here are
preliminary and only show general trends in ozone amounts. In particular,
the calibration of the instrument is such that it reads about 15% lower than a
Dobson at values around 100 DU.
Total column nitrogen dioxide 1997/1998.
Total column nitrogen dioxide and ozone 1998, 1999,
2000, 2001,
2002, 2003,
2004 and 2005.
[Updated 2005 June 28]
There is also a Bentham spectro-radiometer at Rothera.
Provisional values for 1997 / 1998 / 1999
/ 2000 / 2001
/ 2003 / 2004
are available [updated 2004 November 5 ]. The original instrument was
destroyed in a fire on 2001 September 28, however a replacement was commissioned
and became operational on 2003 March 3. For further information on this
data set and permission to use it please contact Paul Geissler at BAS. All
values have been updated to the TOMS 8 algorithm.
Some background information on Halley, Rothera and Faraday stations is available from BAS. Information about Vernadsky station is also available from the Ukrainian Antarctic Centre. Information about Vladimir Ivanovich Vernadsky
Some surface and upper air synoptic data is also available on line from our public data page.
Southern Hemisphere ozone hole movies for
1997/1998 ,
1998/1999 ,
1999/2000 ,
2000/2001 ,
2001/2002 ,
2002/2003 ,
2003/2004 and
2004/2005 [updated 2005 June 10]. A short sequence
of the 2001 hole.
Northern Hemisphere movies for 2000/2001 ,
2001/2002 ,
2002/2003 ,
2003/2004 and
2004/2005
[updated 2005 June 10] A short sequence of ozone depletion during the
2002/03 northern winter showing the difference
from the normal.
These annual movies are each about 8Mb and are compiled from daily TOMS images. They begin
and end in June.
Today's
TOMS global image
The current
area of the hole and other
latest details are available from the NOAA Climate Prediction
Center.
Environment Canada have an excellent set of daily maps showing
both northern and southern ozone levels from a variety of sources.
Requests for permission to use this data or for further information should be sent to Jon Shanklin who maintains these pages.
© Copyright Natural Environment Research Council - British Antarctic Survey 2005 |