The 2011 Antarctic Ozone Hole and Ozone Science Summary: Final Report
Paul Krummel, Paul Fraser and Nada Derek
Centre for Australian Weather and Climate Research
CSIRO Marine and Atmospheric Research
April 2012
OMI - TOMS data used in this report
Data from the Ozone Monitoring Instrument (OMI) on board the Earth Observing Satellite (EOS) Aura, that
have been processed with the NASA TOMS Version 8.5 algorithm, were utilized again in our 2011 weekly
ozone hole reports and in this final report. OMI continues the NASA TOMS satellite record for total ozone
and other atmospheric parameters related to ozone chemistry and climate.
In 2008, stripes of bad data began to appear in the OMI products apparently caused by a small physical
obstruction in the OMI instrument field of view and is referred to as a row anomaly. NASA scientists guess
that some of the reflective Mylar that wraps the instrument to provide thermal protection has torn and is
intruding into the field of view. On 24 January 2009 the obstruction suddenly increased and now partially
blocks an increased fraction of the field of view for certain Aura orbits, which led to the larger stripes of bad
data in the OMI images. Since 5 July 2011, the row anomaly that manifested itself on 24 January 2009 now
affects all Aura orbits, which can be seen as thick white stripes of bad data in the OMI total column ozone
images. Affected data have been flagged and removed from the images. However, once the polar night
reduced enough each year then this was not an issue for determining ozone hole metrics, as there is more
overlap of the satellite passes at the polar regions which essentially ‘fills-in’ these missing data.
In June 2009, all of the OMI ozone data were reprocessed/updated by NASA. These were subsequently
processed by CSIRO, which resulted in small changes in the ozone hole metrics. In mid-2007, a corrected
version of all the Earth Probe TOMS (EPTOMS) data (1996-2005) was released. The correction addressed a
degradation of the scanner mirror on TOMS that resulted in latitudinal dependent calibration errors. An
empirical correction was applied based on the NOAA-16 SBUV/2 ozone record. The above mentioned
reprocessed and corrected datasets are used throughout this report.
The analyses of the 2006 – 2011 Antarctic ozone holes are based on OMI data only, whereas the analysis of
the 2005 hole is based on both OMI and TOMS data, and the analysis of 2004 and earlier holes is based on
TOMS data only.
The 2011 Antarctic ozone hole
Figure 1: Ozone hole ‘depth’ (minimum
ozone, DU) based on OMI and TOMS satellite
data. The 2011 hole (OMI data) is indicated
by the thick black line, the holes for selected
previous years 2006-2010 (OMI data) are
indicated by the thin orange, blue, red, green
and pink lines respectively; the grey shaded
area shows the 1979-2010 TOMS/OMI range
and mean.
Figure 1 shows the Antarctic ozone hole ‘depth’, which is the daily minimum ozone (DU) observed south of
35°S throughout the season. The 2011 ozone hole was relatively deep. The minimum ozone level recorded
in 2011 was 95 DU in early October, the 8th deepest hole recorded. The deepest hole ever was in 2006 (84
Page 1 of 11
DU) during the second week of October, the second deepest in 1998 (86 DU) and the 3rd deepest in 2000
(89 DU).
Figure 2 shows the average amount of ozone (DU) within the Antarctic ozone hole throughout the 2011
season. The minimum average ozone within the hole in 2011 was 151 DU in early October, the 11th lowest
ever recorded, again indicating a relatively deep hole. The lowest reading was in 2000 (138 DU), the second
lowest in 2006 (143 DU) and the 3rd lowest in 1998 (147 DU).
Figure 2: Average amount (DU) of ozone
within the Antarctic ozone hole throughout the
season based on OMI and TOMS satellite
data. The 2011 hole (OMI data) is indicated
by the thick black line, the holes for selected
previous years 2006-2010 (OMI data) are
indicated by the thin orange, blue, red, green
and pink lines respectively; the grey shaded
area shows the 1979-2010 TOMS/OMI range
and mean.
Figure 3 shows the Antarctic ozone hole area (defined as the area within the 220 DU contour) throughout the
2011 season. The maximum daily area of the hole (25.7 million km2 in early October) was the 11th largest
hole ever, the largest in 2000 (29.8 million km2), the 2nd largest in 2006 (29.6 million km 2) and the 3rd largest
in 2003 (28.4 million km 2). The 15-day average ozone hole area for 2011 was 25.0 million km2, the 9th largest
area ever recorded, with the largest in 2000 (28.7 million km 2).
Figure 3: Ozone hole area based on TOMS
and OMI satellite data. The 2011 hole (OMI
data) is indicated by the thick black line, the
holes for selected previous years 2006-2010
(OMI data) are indicated by the thin orange,
blue, red, green and pink lines respectively;
the grey shaded area shows the 1979-2010
TOMS/OMI range and mean.
Figure 4 shows the daily (24 hour) maximum ozone deficit in the Antarctic ozone hole, which is a function of
both ozone hole depth and area. This metric is not the amount of ozone lost within the hole each day, but is
a measure of the accumulated loss summed over the lifetime of ozone within the hole as measured each
day. The maximum daily ozone deficit in 2011 was 37.5 million tonnes (Mt) in early-October, the 9th largest
deficit ever, the largest was in 2006 (45.2 Mt).
Integrated over the whole ozone-hole season, the total ozone deficit (the sum of the daily ozone deficits) was
about 2119 Mt of ozone in 2011, the 7th largest cumulative ozone deficit ever recorded, the largest was in
2006 (2579 Mt).
Page 2 of 11
Figure 4: OMI estimated daily ozone deficit
(in millions of tonnes, Mt) within the ozone
hole. The 2010 hole (OMI data) is indicated
by the thick black line, the holes for selected
previous years 2006-2010 (OMI data) are
indicated by the thin orange, blue, red, green
and pink lines respectively; the grey shaded
area shows the 1979-2010 TOMS/OMI range
and mean. The estimated total (integrated)
ozone loss for each year is shown in the
legend.
Table 1 contains the ranking for all 32 ozone holes recorded since 1979 for the various metrics that measure
the ‘size’ of the Antarctic ozone hole: 1 = lowest ozone minimum, greatest area, greatest ozone loss etc.; 2 =
second largest….
The metric definitions are:

Daily ozone hole area is the maximum daily ozone hole area on any day during ozone hole season.

15-day average ozone hole area is based on a 15-day moving average of the daily ozone hole area.

Ozone hole depth (or daily minima) is based on the minimum column ozone amount on any day
during ozone hole season.

The 15-day average ozone hole depth (or minima) is based on a 15-day moving average of the daily
ozone hole depth.

Minimum average ozone is the minimum daily average ozone amount (within the hole) on any day
during ozone hole season.

Daily maximum ozone deficit is the maximum ozone deficit on any day during ozone hole season.

Ozone deficit is the integrated (total) ozone deficit for the entire ozone hole season.
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Table 1. Antarctic ozone hole metrics based on TOMS/OMI satellite data - ranked by size or minima (Note: 2005 metrics are average of TOMS and OMI data)
Rank
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
15-day average
ozone hole area
Year
106 km2
Daily ozone hole
area maxima
Year
106 km2
15-day average
ozone hole minima
Year
DU
Ozone hole
daily minima
Year
DU
Daily minimum
average ozone
Year
DU
Daily maximum
ozone deficit
Year
Mt
Integrated ozone
deficit
Year
Mt
2000
2006
2003
1998
2008
2001
2005
1996
2011
1993
1994
1992
1999
2007
2009
1997
2010
1987
2004
1991
1989
1990
2002
1985
1986
1984
1988
1983
1982
1980
1981
1979
2000
2006
2003
1998
2005
2008
1996
2001
1993
1999
2011
1994
2007
1997
1992
2009
2004
1987
1991
2010
2002
1989
1990
1985
1984
1986
1988
1983
1982
1980
1981
1979
2006
2000
1998
2001
1999
2011
2003
2009
2005
1993
1996
1997
2008
1992
2007
1991
1987
2004
1990
1989
2010
1985
2002
1986
1984
1983
1988
1982
1980
1981
1979
1994
2006
1998
2000
2003
2001
2005
1991
2011
2009
1999
1997
2008
2004
1996
1993
1992
2007
1989
1987
1990
2010
1985
2002
1986
1984
1983
1988
1982
1980
1979
1981
1994
2000
2006
1998
2003
2005
2001
1999
2009
2008
1996
2011
1997
2007
1993
1992
1991
1987
1990
2010
1989
2004
2002
1985
1986
1984
1983
1988
1982
1980
1979
1981
1994
2006
2000
2003
1994
1998
2008
2001
2005
2011
2009
1999
1997
1996
1992
2007
1993
1991
1987
2010
1990
1989
2002
2004
1985
1986
1984
1983
1988
1982
1980
1981
1979
2006
1998
2001
1999
1996
2000
2011
2008
1994
2005
2003
1993
2009
2007
1997
1992
1987
2010
1990
1991
2004
1989
1985
2002
1986
1984
1988
1983
1982
1980
1981
1979
28.7
27.6
26.9
26.8
26.1
25.7
25.6
25.0
25.0
24.8
24.3
24.0
24.0
23.9
23.9
23.3
21.6
21.4
21.1
21.0
20.7
19.5
17.7
16.6
13.4
13.0
11.3
10.1
7.5
2.0
1.3
0.2
29.8
29.6
28.4
27.9
27.1
26.9
26.8
26.4
25.8
25.7
25.7
25.2
25.1
25.1
24.9
24.4
22.7
22.4
22.3
22.2
21.8
21.6
21.0
18.6
14.4
14.2
13.5
12.1
10.6
3.2
2.9
1.2
93.4
93.5
96.8
98.9
99.9
100.9
101.9
102.6
102.7
104.0
106.0
107.2
108.5
111.5
112.2
113.4
115.7
116.0
117.8
120.4
123.9
131.8
136.0
150.3
156.1
160.3
169.4
183.3
200.0
204.0
214.7
NaN
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84
86
89
91
91
93
94
95
96
97
99
101
102
103
104
105
108
108
109
111
118
124
131
140
144
154
162
170
192
194
195
NaN
138.3
143.3
146.7
147.5
148.6
148.8
149.3
150.0
150.5
150.6
151.2
151.3
154.6
155.2
156.3
162.5
162.6
164.4
164.7
166.2
166.7
169.8
177.1
184.7
190.2
192.3
195.0
199.7
210.0
210.2
210.2
NaN
45.2
44.9
43.4
42.7
41.1
39.6
38.5
37.7
37.5
35.7
35.3
34.5
33.9
33.5
33.0
32.6
26.6
26.2
26.1
24.3
23.6
23.2
22.8
14.5
10.5
9.2
7.0
6.0
3.7
0.6
0.6
0.3
2579.1
2419.9
2298.2
2249.6
2175.7
2164.0
2119.3
2000.2
1981.8
1901.0
1893.6
1832.9
1809.0
1785.1
1758.6
1528.6
1365.6
1339.9
1180.7
998.3
974.7
916.7
629.6
574.8
346.2
255.5
197.6
184.0
73.1
12.8
3.5
1.0
Figure 5 shows the 15-day moving average of the minimum daily column ozone levels recorded in the hole
since 1979 from TOMS and OMI data. This metric shows a consistent downward trend in ozone minima from
the late 1970s until the mid-to-late-1990s, with a possible sign of ozone recovery by 2011. The 1996-2001
mean was 100±5 DU, while the 2006-2011 mean was 107±11 DU. There is the suggestion that ozone is
recovering but the uncertainties are such that the recovery is not statistically significant.
Figure 5: Minimum ozone levels observed in the Antarctic ozone hole using a 15-day moving average of the minimum
daily column ozone levels during the entire ozone season for all available years of TOMS (blue) and OMI (red) data. The
polynomial fit (order 3) does not include the unusual (warm year) data seen in 1988 and 2002. The error bars represent
the range of the daily ozone minima in the 15-day average window.
Salby et al. (2011) have suggested that the satellite ozone data over Antarctica since 1997 are showing
significant ozone recovery once the dynamically-induced ozone changes are removed from the ozone data.
If we remove the significantly dynamically-influenced 2002 ozone data from Figure 5, the remaining data
(1996-2011) show signs of ozone growth (recovery) of 0.6±0.4 (1σ) DU/yr.
Figure 6 shows the minimum daily average ozone levels within the ozone hole from 1979 to 2011 from
TOMS and OMI data. This metric shows a consistent downward trend in average ozone from the late-1970s
until the mid-1990s, with some sign of ozone recovery by 2011. The 1996-2001 mean was 148±5 DU while
the 2006-2011 mean was 152±7 DU. Again this is suggestive of the commencement of ozone recovery, but
the uncertainty intervals overlap.
If we remove the significantly dynamically-influenced 2002 and 2004 ozone data from Figure 6, the
remaining data (1996-2011) show signs of ozone growth (recovery) of 0.5±0.3 (1σ) DU/yr.
Figure 6: The minimum daily average column ozone levels within the ozone hole during the entire ozone season for all
available years of TOMS (blue) and OMI (red) data. The polynomial fit (order 3) does not include the data seen in the
years (1988, 2002 and 2004) when the stratosphere was unusually warm.
Figure 7 shows the maximum ozone hole area (15-day average) recorded since 1979 from TOMS and OMI
data. Disregarding the two unusual years (1988, 2002) when the polar vortex broke up early, this metric
suggests that the ozone hole has stopped growing, but has not yet started to decline in area. The 1996-2001
Page 5 of 11
mean was (25.6±2.0) x106 km2, while the 2006-2011 mean was (24.7±2.1) x106 km2, again indicative of the
commencement of possible ozone recovery, but not statistically significant.
If we remove the significantly dynamically-influenced 2002 and 2004 ozone data from Figure 7, the
remaining data (1997-2011) do not show a significant decrease in ozone hole area. The data suggest that a
maximum in ozone hole area occurred after 1997, close to 2000.
Figure 7: Maximum ozone hole area (area within the 220 DU contour) using a 15-day moving average during the ozone
hole season, based on TOMS data (blue) and OMI data (red). The polynomial fit (order 3) does not include the unusual
data seen in 1988 and 2002. The error bars represent the range of the ozone hole size in the 15-day average window.
Figure 8 shows the integrated ozone deficit (Mt) from 1979 to 2011. The ozone deficit rose steadily from the
late-1970s until the late-1990s/early 2000s, where it peaked at approximately 2300 Mt, and then started to
drop back down. Excluding the warm years 2002 and 2004, this metric does not show evidence of
statistically significant ozone recovery. The 1996-2001 mean was 2180±230 Mt while the 2006-2011 mean
was 1940±410 Mt, suggesting the commencement of ozone recovery, but these means overlap significantly
at the 1σ level.
If we remove the significantly dynamically-influenced 2002 and 2004 ozone data from Figure 8, the
remaining data (1996-2011) show a signs of a decline in ozone deficit 25±16 (1σ) Mt/yr.
Figure 8: Estimated total ozone deficit for each year in millions of tonnes (Mt), based on TOMS (blue) and OMI (red)
satellite data. The solid line is a polynomial fit (order 3) to the data (TOMS up to 2005, OMI 2006 onwards) excluding the
anomalously warm years of 1988, 2002 and 2004 (open squares).
The most quoted (though not necessarily the most reliable) metric in defining the severity of the ozone hole
is the average minimum ozone levels observed over Halley Station (British Antarctic Survey), Antarctica,
throughout October (Figure 9). This was the metric that was first reported in 1985 to identify the significant
ozone loss over Antarctica. Based on this metric alone, it would appear that October mean ozone levels over
Halley may have started to increase again. The minimum ozone level was observed in 1993, which has been
attributed to residual volcanic effects (Mt Pinatubo, 1991). Ignoring the warm years of 2002 and 2004, the
mean October ozone levels at Halley Station for 2005 to 2011 (155±16 DU) are higher than those observed
from 1996 to 2001 (141±4 DU), although the 1 σ uncertainties just overlap.
Page 6 of 11
If we remove the significantly dynamically-influenced 2002 and 2004 ozone data from Figure 9, the
remaining data (1996-2011) show significant ozone growth (recovery) of 1.4±0.7 (1σ) DU/yr. For the period
1993-2011 the ozone growth is 1.8±0.5 (1σ) DU/yr, although the early 1990s data may be low due to the
impact of the Mt Pinatubo eruption.
Figure 9: Total column ozone amounts (October mean) as measured at Halley Station, Antarctica, by the British
Antarctic Survey from 1956 to 2011. The green line is a polynomial fit (order 3) to the data excluding the anomalously
warm years of 1986, 1988, 2002 and 2004.
Antarctic Ozone Recovery
Ozone recovery over Antarctica is complex to model. Apart from the future level of ozone depleting chlorine
in the stratosphere, temperature trends and variability in the stratosphere, the impact of major volcanic
events and the future chemical composition (for example H 2O, CH4 and N2O) of the stratosphere are likely to
be important factors in determining the rate of ozone recovery. Model results and observations show that the
solar cycle changes have maximum impact on tropical ozone and do not significantly impact on stratospheric
ozone levels over Antarctica.
Chlorine levels are likely to decline steadily over the next few decades at about 1% per year, leading to
reduced ozone destruction. Figure 10 shows Equivalent Chlorine (ECl) and Effective Equivalent Chlorine
(EECl), and their lagged values for the Antarctic (6 years) and mid-latitude (3 years) stratospheres, as
described by Hofmann and Montzka (2009), but here derived from CSIRO and AGAGE global
measurements of ODSs, including Cape Grim measurements and measurements in air trapped in Antarctic
firn from Law Dome, Antarctica. ECl is relevant to ozone depletion over Antarctica while EECl is relevant to
ozone depletion at mid-latitudes.
ECl and EECl peaked at 4.5 ppb in 1995 and 3.3 ppb in 1994 respectively, falling to 4.1 and 2.8 ppb by
2011, declines of 9% and 15% respectively. Table 3 shows the species contributing to the declines in ECl
(0.35 ppb) and the decline in EECl (0.41 ppb) since their peak values in 1995 and 1994 respectively. The
decline since 1994/95 to 2011 is dominated by methyl chloroform, followed by methyl bromide, the CFCs
and carbon tetrachloride. The halons and HCFCs have made an overall growth contribution to ECl and EECl
since 1994/95.
The initial (1-2 decades) decline in ECl and EECl have been and will be dominated by the shorter-lived
ODSs, such as methyl chloroform and methyl bromide, whereas the long-term decline will be dominated by
CFCs and carbon tetrachloride. Based on ECl and EECl values from scenarios of ODS decline (Daniel and
Velders, 2007), ozone recovery at mid-latitudes will occur at about the late-2040s and ozone recovery in the
Antarctic stratosphere will occur about the late-2070s.
Hoffman and Montzka (2009) have defined an index that neatly describes the state of the atmosphere, in
relation to stratospheric halogen (chlorine plus bromine) levels and ozone recovery at mid-latitudes (ODGIML) and over Antarctic (ODGI-A) – see discussion below. Figure 11 shows the CSIRO version of the ODGIML and ODGI-A indices derived from global AGAGE data including data from Cape Grim. Based on data up
to 2011, the ODGI-A and ODGI-ML indices have declined by 17% and 34% respectively since peak ECl and
EECl values in 1995, indicating that the atmosphere is 17% and 34% along the way toward a halogen level
that should allow an ozone-hole free Antarctic stratosphere and a ‘normal’ (pre-1980s) ozone layer at midPage 7 of 11
latitudes. The CSIRO version of the ODGI uses ODS fractional release factors from Daniel and Velders
(2007).
Table 3: Individual ODS contributions to the decline in ECl and EECl observed in the atmosphere in 2011 since their
peak values (4.5 ppb in 1995 and 3.3 ppb in 1994 respectively).
Species
ECl decline
ppb Cl
EECl decline
ppb Cl
methyl chloroform
methyl bromide
CFCs
carbon tetrachloride
halons
HCFCs
Total decline
0.29
0.13
0.10
0.06
-0.09
-0.15
0.35
0.29
0.13
0.08
0.06
-0.09
-0.06
0.41
Figure 10: Equivalent and Effective Equivalent Chlorine (ECl, EECl – see text) derived from global measurements of all
the major ODSs at Cape Grim and other AGAGE stations and in Antarctic firn air from Law Dome. ECl is lagged 6 years
as a driver of Antarctic ozone depletion (dashed line), EECl is lagged 3 years as a driver of mid-latitude ozone depletion
(dashed line). Arrows indicate dates when the mid-latitude and Antarctic stratospheres return to pre-1980s and preozone hole levels respectively.
Figure 11: ODGI-A and ODGI-ML indices (Hofmann and Montzka, 2009) derived from AGAGE ODS data using ODS
fractional release factors from Daniel and Velders (2007).
Page 8 of 11
Figure 12 compares changes in ECl since the late 1970s to the cumulative ozone deficit as shown in Figure
8. Apart from the years with unusually warm stratospheres (1988, 2002, 2004, not shown), there is a strong
correlation between ECl changes and cumulative ozone deficit (corr. coeff = 0.90), strongly supporting the
dominant role of ECl in determining long term ozone trends over Antarctica and indicating that ozone
recovery will become significant as ECl continues to fall (in the absence of major volcanic event(s) impacting
on the stratosphere) over the next decade or more. Each ppb of ECl is responsible for about 1500 Mt of
stratospheric O3 deficit within the hole.
A similarly strong correlation (corr. coeff = -0.97) of ECl and ozone changes over Antarctica is also seen
since the late 1950s-early 1960s, using the Halley Station ozone record (Figure 12). The warm stratosphere
years (1986, 1988, 2002, 2004, not shown) do not fit this correlation and there is a suggestion of enhanced
ozone depletion (up to 10%) in the post-Pinatubo years (1993-1995). Even if these Pinatubo-affected data
are not considered, there is still evidence of significant ozone recovery in the Halley data. Each ppb of ECl is
responsible for about 50 DU of O3 loss in the stratosphere over Halley in October.
These data suggest that a 3-4 year lag for ECl based on tropospheric observations is more appropriate to
correlate with stratospheric ozone metrics over Antarctica.
Figure 12: Cumulative ozone deficit (Mt, Figure 10) in
the Antarctic ozone hole and annual ECl changes (ppb,
3 year lag, solid line) since the late 1970s to 2011.
Figure 13: Ozone changes (October monthly mean
data) seen at Halley Station, Antarctica, since the mid1950s to mid-1960s compared to the annual changes in
ECl (difference from 1956-1962 mean) over the same
time frame, 1960-2011 (with a 3 year lag).
Page 9 of 11
Summary
 The 2011 Antarctic ozone hole was relatively large compared to holes from the past 15 years. The
2011 hole ranked between 6th-11th over a number of metrics for the 32 holes assessed since 1979.
 The 2000 and 2006 ozone holes were the largest ozone holes ever, depending on the metric that is
used.
 Most ozone metrics discussed in this report show signs that ozone recovery has commenced, once
the influence of the dynamically-impacted ozone data from 2002 and 2004 are removed from the
ozone record.
 Comparison of trends in ECl and cumulative ozone deficit within the hole since the late 1970s suggest
that ozone recovery may have commenced
 The ECl data from observations and future scenarios suggest that ozone recovery at mid-latitudes will
occur at about the early-2050s and Antarctic ozone recovery at about the late-2070s.
 The ODGI vales suggest that the atmosphere is about 17% along the path to Antarctic ozone recovery
and 34% along the path to ozone recovery at mid-latitudes.
 Changes in ECl and changes in ozone over Antarctica (satellite and Dobson) are highly correlated and
the Dobson data at Halley Station suggest Antarctic ozone recovery has commenced. The correlation
could be even more significant if temperature effects were removed from the ozone data.
 The data suggest that a lag time of 3-4 years is more appropriate than the recommended 6 years for
ECl over Antarctica, based on AGAGE global observations of ODSs
Animations of the daily images from the 2011 ozone hole in both animated GIF and AVI formats can be
downloaded from ftp://gaspublic:gaspublic@ftp.dar.csiro.au/pub/ozone_hole/. Animations of the historical
October 1-15 averages for all available years in the period 1979-2011 are also contained in this directory. To
download, right click the file and select ‘Copy to folder …’.
Definitions
CFCs: chlorofluorocarbons, synthetic chemicals containing chlorine, once used as refrigerants, aerosol
propellants and foam-blowing agents, that break down in the stratosphere (15-30 km above the earth’s
surface), releasing reactive chlorine radicals that catalytically destroy stratospheric ozone.
DU: Dobson Unit, a measure of the total ozone amount in a column of the atmosphere, from the earth’s
surface to the upper atmosphere, 90% of which resides in the stratosphere at 15 to 30 km.
Halons: synthetic chemicals containing bromine, once used as fire-fighting agents, that break down in the
stratosphere releasing reactive bromine radicals that catalytically destroy stratospheric ozone. Bromine
radicals are about 50 times more effective than chlorine radicals in catalytic ozone destruction.
Ozone: a reactive form of oxygen with the chemical formula O3; ozone absorbs most of the UV radiation
from the sun before it can reach the earth’s surface.
Ozone Hole: ozone holes are examples of severe ozone loss brought about by the presence of ozone
depleting chlorine and bromine radicals, whose levels are enhanced by the presence of PSCs (polar
stratospheric clouds), usually within the Antarctic polar vortex. The chlorine and bromine radicals result from
the breakdown of CFCs and halons in the stratosphere. Smaller ozone holes have been observed within the
weaker Arctic polar vortex.
Polar night terminator: the delimiter between the polar night (continual darkness during winter over the
Antarctic) and the encroaching sunlight. By the first week of October the polar night has ended at the South
Pole.
Polar vortex: a region of the polar stratosphere isolated from the rest of the stratosphere by high west-east
wind jets centred at about 60°S that develop during the polar night. The isolation from the rest of the
atmosphere and the absence of solar radiation results in very low temperatures (less than -78C) inside the
vortex.
PSCs: polar stratospheric clouds are formed when the temperatures in the stratosphere drop below -78C,
usually inside the polar vortex. This causes the low levels of water vapour present to freeze, forming ice
crystals and usually incorporates nitrate or sulphate anions.
Page 10 of 11
TOMS: the Total Ozone Mapping Spectrometer, is a satellite borne instrument that measures the amount of
back-scattered solar UV radiation absorbed by ozone in the atmosphere; the amount of UV absorbed is
proportional to the amount of ozone present in the atmosphere.
UV radiation: a component of the solar radiation spectrum with wavelengths shorter than those of visible
light; most solar UV radiation is absorbed by ozone in the stratosphere; some UV radiation reaches the
earth’s surface, in particular UV-B which has been implicated in serious health effects for humans and
animals; the wavelength range of UV-B is 280-315 nanometres.
Acknowledgements
The TOMS and OMI data are provided by the TOMS ozone processing team, NASA Goddard Space Flight
Center, Atmospheric Chemistry & Dynamics Branch, Code 613.3. The OMI instrument was developed and
built by the Netherlands's Agency for Aerospace Programs (NIVR) in collaboration with the Finnish
Meteorological Institute (FMI) and NASA. The OMI science team is lead by the Royal Netherlands
Meteorological Institute (KNMI) and NASA. This research is carried out under contract from DEWHA to
CAWCR.
References
Daniel, J., & G. Velders, Halocarbon Scenarios, Ozone Depletion Potentials, and Global Warming Potentials, Chapter 8
in Scientific Assessment of Ozone Depletion 2006, Global Ozone Research and Monitoring Project-Report No. 50,
8.1- 8.39, WMO, Geneva, Switzerland, 2007.
Hofmann, D & S. Montzka, Recovery of the ozone layer: the Ozone Depleting Gas Index, Eos, 90: 1, 1-2, 2009.
Salby, M., E. Titova & L. Deschamps, Rebound of Antarctic ozone, Geophys. Res. Letts., 38, L09702,
doi:10.1029/2011GL047266, 2011.
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