The 2015 Antarctic Ozone Hole Summary: Report #14, Monday 16 November 2015
Paul Krummel and Paul Fraser
CSIRO Oceans and Atmosphere
Aspendale, Victoria
Summary
For the 2015 ozone hole we will again be reporting images and metrics calculated from both the OMI and
OMPS data products (see the instrumentation section for a description of these). Please note that due to
operational reasons, the OMPS Level 3 global gridded daily total ozone column products provided by NASA
run 4-5 days behind the current day.
August
By mid-August, the onset of the 2015 ozone hole was yet to start. This is the latest onset of the ozone hole
that has been seen since the mid-to-late 1980s. The mid-to-lower Antarctic stratospheric temperatures
have been colder than usual in late July/early August, with a less-than-normal stratospheric heat flux
towards the pole from mid-July onwards. On 18 August the 2015 ozone hole had begun and by 21 August
the ozone hole area had risen to 2.9 million km2 and the ozone minima had dropped to 191 DU. The low-tomid Antarctic stratospheric temperatures remained colder than usual during the third week of August. The
fourth week of August saw moderate growth in the ozone hole area, reaching 6.3 million km 2 on 26 August,
while the ozone minima showed quite a bit of variability fluctuating between 164 and 202 DU. The low-tomid Antarctic stratospheric temperatures remained colder than usual during the fourth week of August.
September
The last few days of August, beginning of September saw the ozone hole area increase rapidly to be
approximately 15 million km2 by 4 September, but large variability remained in the ozone hole minima,
dropping to 161 DU on 1 September before rising again to 184 DU on 4 September. The low-to-mid
Antarctic stratospheric temperatures remained colder than usual during this period. The period of 5-11
September saw the ozone hole area continue to grow, reaching 21.5 million km2 by 11 September, but the
ozone hole is yet to fully close for 2015. The variability on the ozone minima has reduced considerably, with
the minima dropping to a low of 156 DU during this period. The colder than usual low-to-mid Antarctic
stratospheric temperatures continued during this period. By 18 September the ozone hole area had
reached 25.9 million km2, so far the largest recent ozone hole since 2008. However, while this years’ hole is
relatively large in area, it is of only average ‘depth’. The low-to-mid Antarctic temperatures remain colder
than usual, indicating a stable vortex. The period of 19-25 September saw the ozone hole area continue to
grow, reaching 26.4 million km2 by 24 September. This may be the maximum area this year and is about the
9th largest area ozone hole ever. Current stratospheric temperatures are at record lows. The ozone hole
(vortex) has been stable and symmetric for nearly 2 weeks during which all 3 coastal Australian Antarctic
stations have been within the hole – this is unusual. Ozone over Macquarie Island appears unusually low –
no significant ozone ridge between Australia and Antarctica. Ten years ago, with higher chlorine levels, it is
possible that a vortex of this stability and low temperatures may have resulted in record ozone losses.
October
The last days of September and beginning of October saw the ozone hole area continue to grow, with the
daily area reaching 28.1 million km2 on 2 October, now the 4th largest hole on record in terms of this metric.
The 3 larger holes were in 2000 (29.8 million km2), 2006 (29.6 million km2) and 2003 (28.4 million km2). The
ozone deficit continued to rise during this period to be at 35.9 Mt by 2 October, placing the 2015 hole in
the top 10 highest daily ozone deficits so far. Current stratospheric temperatures remain at record lows and
the ozone hole (vortex) has been stable and symmetric for nearly 3 weeks during which all 3 coastal
Australian Antarctic stations have been within the hole. The period of 3-8 October saw the stratospheric
temperatures continue to remain at record lows and the ozone hole (vortex) has been stable and
symmetric for nearly 4 weeks during which all 3 coastal Australian Antarctic stations have been within the
hole. After a small dip during 3-5 October, the ozone hole area peaked again at 28.15 million km2 on 6
October, still the 4th largest hole on record. Since 28 September, the ozone hole area, as seen by the OMI
instrument, has been at record levels exceeding all the previous maxima for this time of year. On 8 October
the daily ozone deficit just exceeded the 2011 maximum, reaching 37.6 million tonnes, making it the 8 th
largest on record so far.
During the second week of October the ozone hole area peaked again at 28.13 million km 2 on 6 October
before slowly reducing in size to be about 26 million km2 on 16 October We have most likely seen the
maximum daily area for this year at 28.15 million km2 on 6 October, confirming its place as the 4th largest
hole on record in terms of this metric. The OMI ozone hole area continues to be at record levels exceeding
all the previous maxima for this time of year. The second week of October saw the daily ozone deficit peak
at 37.7 million tonnes on 9 October before dropping to 33.2 million tonnes by 16 October. This is likely to
be the maximum value for this year, which places it equal 7th largest on record. The ozone hole minima has
plateaued during the first half of October, with the average minima from the OMI instrument being around
107 DU. Interestingly, the OMPS ozone hole minima dropped to 95 DU on 8 October and remained around
this value up to the last available data from 11 October, which is considerably lower than what is seen by
OMI. Based on the minima from OMPS, then this years’ hole would rank equal (with 2011) 8 th lowest on
record. The second week of October saw the stratospheric temperatures continue to remain at record lows
and the ozone hole (vortex) continued to be very stable. From 12 to 16 October a ridge of higher ozone has
formed immediately south of Australia, which has had the effect of nudging the polar vortex/ozone hole
slightly towards South America.
The period of 17-24 October saw the daily ozone hole area increase again to almost 27 million km2 before
levelling off at approximately 26.5 million km2. The size of the ozone hole since 28 September is
unprecedented, with the daily area now 3-4 million km2 higher than the previous maximum levels for the 5
day period of 20-24 October. Likewise, the daily ozone hole deficit has been at record levels since 17
October exceeding all the previous maxima, with the maximum levels for the 5 day period of 20-24 October
being 3.5-4.5 million tonnes higher than previous maxima. The ozone hole minima seen on 23 & 24 October
are now the lowest on record for this time of year, being 1-3 DU lower than the previous minima. The
stratospheric temperatures during 17-24 October remained at record lows, especially at the 100 hPa level,
and the ozone hole (polar vortex) was very stable and symmetric, during which all 3 coastal Australian
Antarctic stations have been within the hole.
The last week of October has seen the ozone hole start to slowly decrease in area to be at 23.8 million km 2
by 30 October. This is, however, still very large for this time of year and remains well above the previous
maximum levels. By the end of October the daily ozone deficit had dropped to about 27.1 million tonnes,
however, this is still above the previous maxima for this time of year. What will be of interest from now is
what the total integrated ozone deficit will be for the year when the ozone hole closes – it is currently at
about 1640 million tonnes, and if the current trend continues, it is likely to end up more than 2000 million
tonnes. The images from 25 October through to 1 November (note that 31 Oct & 1 Nov images from OMI
are only partial coverage) show that the ozone hole has started to become distorted, indicating some wave
activity affecting the polar vortex, which is likely to entrain warmer air from lower latitudes. While the 6090S zonal mean temperatures at both the 50 & 100 hPa levels were still at record low levels at the end of
October, the forecast data indicate that these are likely to increase in the coming week.
November
The distortion of the polar vortex/ozone hole mentioned last week continued during 2-5 November, such
that the tip of South America was within the ozone hole on 3 & 4 November as the distortion propagated
through and all 3 of the Australian Antarctic stations were outside of the hole on these two days. This
corresponded to a rapid increase in the 60-90S zonal mean temperatures at both the 50 & 100 hPa levels,
as forecasted. The result is that the ozone hole area dropped sharply on 5 November to about 20 million
km2, and the daily ozone deficit dropped sharply on 4-5 November to 18.3 million tonnes, both of these
metrics are now well below the previous maxima for this time of year. This indicates that the recovery of
the ozone hole this year has started.
The second week of November saw the ozone hole recovery continue, with the ozone minima increasing
sharply to 154 DU on 10 November, before slightly decreasing again to be 146 DU by 12 November, the
ozone deficit continued to drop to end up at 16.9 million tonnes by 12 November, and the ozone hole area
remaining around the 20 million km2 mark. The distortion of the ozone hole continued until 11 November,
with the image from 12 November showing signs of becoming symmetrical again. The second week of
November saw the 60-90S zonal mean temperatures at 50 hPa & 100 hPa track along the edge of the 30 th
percentile mark and lower bound of the 1979-2014 range, respectively. The forecast data indicate that
these trends at the 50 & 100 hPa levels will continue, despite the increase in the forecasted heat flux.
The 2015 ozone hole
Ozone hole area
By mid-August, the 2015 ozone hole had essentially yet to appear, with the OMI data indicating no area
where the total column ozone was less than 220 DU. The OMPS data indicate some small excursions below
220 DU in early August, but nothing since. This is the latest onset of the ozone hole since the mid-to-late
1980s.The 2015 ozone hole finally started to form on 18 August, and by 21 August the ozone hole area had
grown to 2.9 million km2. The ozone hole area continued to grow during the fourth week of August
reaching 6.3 million km2 on 26 August before dropping back to just under 5 million km2 on 27 August. The
development of this years’ hole based on this metric is similar to the 2010 ozone hole, which was also a late
developing hole but was a persistent hole as well.
The last few days of August, beginning of September saw the ozone hole area increase rapidly to be
approximately 15 million km2 by 4 September, which was close to the long-term 1979-2014 average for this
time of year, and similar to the 2012 & 2014 ozone holes. The ozone hole continued to grow during the
second week of September, reaching 20.9 million km2 on 7 September before dropping back to 18.7 million
km2 on 9 September and increasing again to 21.5 million km2 on 11 September. This variability is due to the
ozone hole not yet being completely closed. On 11 September, the ozone hole area was very close to the
2013 ozone hole on the same date. During the third week of September, the ozone hole area rose sharply
again to be 25.9 million km2 on 18 September and 26.4 million km2 on 24 September, which is now the 9th
largest hole in terms of daily area, just below the 2001 hole (which was also 26.4 million km2). It appears
that this may be the maximum area for 2015, but the maximum can occur as late as early October, so we
should wait until early October to rate the 2015 hole in area terms.
The last days of September and beginning of October saw the ozone hole area continue to grow, with the
daily area reaching 28.1 million km2 on 2 October, now the 4th largest hole on record in terms of this metric.
The 3 larger holes were in 2000 (29.8 million km 2), 2006 (29.6 million km2) and 2003 (28.4 million km2). If
this years’ hole continues to grow then it may move even further up the ranking; the coming week will
most likely determine this. The first week of October saw the ozone hole area drop slightly to 26.9 million
km2 on 4 October before rising again to 28.15 million km2 on 6 October, and remaining approximately at
this level until 8 October. Since 28 September, the ozone hole area, as seen by the OMI instrument, has
been at record levels exceeding all the previous maxima for this time of year. There appears to be a small
offset between the OMI and OMPS instruments for this metric since mid-September, with OMPS being
slightly lower. During the second week of October the ozone hole area peaked again at 28.13 million km 2
on 6 October before slowly reducing in size to be about 26 million km 2 on 16 October. We have most likely
seen the maximum area for this year at 28.15 million km 2 on 6 October, confirming its place as the 4th
largest hole on record in terms of this metric. The OMI ozone hole area continues to be at record levels
exceeding all the previous maxima for this time of year, which is clearly seen in the top panel of Figure 1.
For perspective, the previous years that were plotted in Figures 1 and 2 have been changed to include the
four largest ozone hole years (1998, 2000, 2003 & 2006). The period of 17-24 October saw the daily ozone
hole area increase again to almost 27 million km2 before levelling off at approximately 26.5 million km2. The
size of the ozone hole for this time of year is now unprecedented, with the daily area now 3-4 million km2
higher than the previous maximum levels for the 5 day period of 20-24 October, which is clearly seen in the
top panel of Figure 1. The last week of October has seen the ozone hole start to slowly decrease in area to
be at 23.8 million km2 by 30 October. This is, however, still very large for this time of year and remains well
above the previous maximum levels.
The first week of November saw the daily ozone hole area drop sharply on 5 November to about 20 million
km2, indicating that the recovery of the ozone hole this year has started. During the second week of
November the daily ozone hole area increased briefly to 22.3 million km2 on 6 November before dropping
back to fluctuate around 20 million km2, ending at 20.7 million km2 on 12 November, still above the
previous maximum level for this time of year.
Ozone deficit
The bottom panel of Figure 1 shows that by mid-August there was no estimated daily ozone deficit to date.
By the end of the third week of August the estimated daily ozone deficit had reached 1 million tonnes. The
fourth week of August saw the daily ozone deficit remain quite low below 2 million tonnes.
The beginning of September saw the daily ozone hole deficit reach 5 million tonnes before dropping back to
about 4 million tonnes by 4 September. This is well below the long-term 1979-2014 average for this time of
year and is similar to the 2010 ozone hole. During the second week of September the ozone deficit
continued to grow reaching 11.7 million tonnes by 11 September, which was still below the long-term
1979-2014 average for this time of year. The third week of September saw the ozone deficit double from
the previous week to be 21.6 million tonnes by 18 September, a few million tonnes above the long-term
1979-2014 average for this time of year. By 25 September the deficit had risen to 29.2 Mt and apparently
still rising, well above the long-term average and second only since 2010 to the 2011 hole.
The ozone deficit continued to rise during the last days of September and early October to be at 35.9 Mt by
2 October with indications that it is still rising. This is now approaching the 2011 ozone deficit, and it now
places the 2015 hole in the top 10 highest daily ozone deficits so far. On 8 October the daily ozone deficit
just exceeded the 2011 maximum, reaching 37.6 million tonnes, making it the 8 th largest on record so far.
The second week of October saw the daily ozone deficit peak at 37.7 million tonnes on 9 October before
dropping to 33.2 million tonnes by 16 October. This is likely to be the maximum value for this year, which
places it equal 7th largest on record. The daily ozone hole deficit has been at record levels since 17 October
exceeding all the previous maxima, with the maximum levels for the 5 day period of 20-24 October being
3.5-4.5 million tonnes higher than previous maxima. By the end of October the daily ozone deficit had
dropped to about 27.1 million tonnes, however, this is still above the previous maxima for this time of year.
What will be of interest from now is what the total integrated ozone deficit will be for the year when the
ozone hole closes – it is currently at about 1640 million tonnes, and if the current trend continues, it is
likely to end up more than 2000 million tonnes.
Similar to the ozone hole area, the daily ozone deficit dropped sharply on 4-5 November to 18.3 million
tonnes, now well below the previous maxima for this time of year. The daily ozone deficit continued to
drop during the second week of November to end up at 16.9 million tonnes by 12 November.
Ozone hole minima
By mid-August the OMI ozone minima had not yet dropped below the 220 DU threshold, but was expected
to do so in the following week (current minima is approximately 225 DU). The OMPS minima did fall below
220 DU on 3, 5 & 6 August due to a few ‘pixels’ right at the polar vortex edge reaching just below this
threshold. On 18 August the ozone minima dropped sharply below 220 DU indicating the beginning of the
2015 ozone hole, and by 21 August the minima had dropped to 191 DU, close to the long-term 1979-2014
average. The OMPS minima appears to have dropped below, and remained below 220 DU, 2-3 days earlier
than the OMI data show, but the timing of the onset can be uncertain due to the large variability in this
metric during the first few weeks of August. The daily ozone minima continued to be quite variable during
the fourth week of August dropping to 164 DU on 24 August before increasing to 202 DU on 27 August. The
variability in this metric was expected to reduce in the next one to two weeks as the polar night reduces.
The variability in the ozone hole minima continued during the last days of August through early September,
dropping to 161 DU on 1 September before rising again to 184 DU on 4 September. By 8 September the
ozone minima had reached 156 DU, before rising slightly to 159 DU by 11 September, which is very close to
the long-term 1979-2014 average. The large variability in the ozone minima has now reduced considerably.
The third week of September saw the ozone deficit drop to 140 DU on 15 September, then rise to 154 DU
on 17 September before dropping again to 145 DU on 18 September, once again very close to the long-
term 1979-2014 average. By 25 September the ozone minima dropped to 130 DU, just below the long-term
average and similar to 2014.
The past week saw the ozone minima drop sharply to be at 113 DU by 2 October, which is now below the
long-term 1979-2014 average. Typically, this metric reaches a minimum in the last week of September
through to the first two weeks of October, so we should know how this years’ hole will rank in the next few
weeks. The ozone minima continued to drop during the first week of October, reaching 101 DU on 4
October before rising slightly to 109 DU on 6 October and then back to 103 DU on 8 October. This is getting
close to being in the top ten lowest minima, but not quite yet. The second week of October saw the ozone
hole minima from OMI plateau, with the average across the first half of October being around 107 DU.
Interestingly, the OMPS ozone hole minima dropped to 95 DU on 8 October and remained around there
until the last available data from 11 October, which is considerably lower than what is seen by OMI. Based
on the minima from OMPS, then this years’ hole would rank equal (with 2011) 8 th lowest on record. During
17-24 October the ozone column minima increased slightly averaging 112 DU, however, normally at this
time of year the ozone minima starts to increase, such that on 23 & 24 October this years’ minima is now
the lowest on record for this time of year, being 1-3 DU lower than the previous minima. During the last
week of October the ozone hole minima started to increase again, and is tracking along the edge of
previous lowest minima. By 30 October the minima had increased to ~120 DU.
The ozone minima increased steadily during the first week of November to be at 136 DU on 5 November,
now somewhat higher than the previous lowest minima for this time of year. The second week of
November saw the ozone minima increase sharply to 154 DU on 10 November, before slightly decreasing
again to be 146 DU by 12 November.
Average ozone in the hole
The average ozone amount in the hole (averaged column ozone amount in the hole weighted by area;
Figure 2 bottom panel) shows that the ozone hole for 2015 had yet to commence by mid-August. During
the third week of August the average amount of ozone in the hole dropped rapidly to be at 203 DU on 21
August. Similar to the ozone minima, this metric showed quite a bit of variability, dropping to 195 DU on 24
August before rising again to 213 DU on 27 August.
The average ozone amount in the hole also continued to show quite a bit of variability, dropping to 194 DU
on 1 September before rising again to 207 DU on 4 September. The large variability in this metric has now
reduced, with the average ozone amount in the hole falling to 194 DU on 11 September. The average ozone
amount in the hole decreased steadily during the third week of September to reach 181 DU by 18
September, very close to the long-term 1979-2014 average. By 25 September the average ozone in the hole
has dropped to 167 DU, significantly below the long-term average and similar to the 2013 and 2014 holes.
The average ozone amount in the hole continued to decrease to 160 DU on 2 October, still significantly
below the long-term average and similar to the 2014 hole for this time of year. The minima dropped further
during the first week of October reaching 157 DU, now below the minimum value recorded in 2014. The
average ozone amount in the hole remained at approximately 157 DU during 9-12 October before rising
slightly to 160 DU on 16 October. Similar to the other metrics, this will most likely be the minimum value
for this metric for 2015, placing it around 16th lowest on record. The average ozone amount in the hole
remained at approximately 160 DU until 23 October when it increased slightly to end up at 162 DU by 24
October. As of 30 October, the average ozone amount in the hole continued to increase and was at 167 DU,
very similar to the 1998 ozone hole.
On 4-5 November the average ozone amount in the hole increased rapidly to 177 DU, now higher than the
1998 ozone hole for the same time of year. The second week of November saw a steady increase in the
average amount of ozone in the hole to end at 182 DU by 12 November.
Total column ozone images
Total column ozone data over Australia and Antarctica for 28 October-12 November 2015 from OMI are
shown in Figure 3 and for 23 October-7 November 2015 from OMPS are shown in Figure 4.
By the end of the second week of August the Antarctic polar night region still covered most of Antarctica,
with essentially no sign yet of any areas below the 220 DU threshold that defines the Antarctic ozone hole.
What is quite evident, compared to recent years, is the lack of the strong ridge of high ozone in the band
immediately south of Australia between about 40-60S. The areas of higher ozone that are present in this
latitude band appear to be patchy, possibly indicating some wave activity. The third week of August saw
the 2015 ozone hole begin to form, which can be seen as small areas indicated by the red 220 DU contour
predominantly in the region of 150W to 60W at around 70S during 18-21 August. During the fourth
week of August the ozone hole continued to form in the region of 0W to 90W before propagating to the
region between 0E to 120E. On 28 August, the Australian Antarctic stations of Mawson and Casey were
within the 220 DU contour.
The formation of the 2015 ozone hole can be clearly seen in the images from 30 August through to 4
September, as the red 220 DU contour progressively grew during this period. It is expected that the 2015
ozone hole will fully form during the next week, which will see the areas below 220 DU completely join up
and the 220 DU contour will close to encircle the Antarctic continent. The Australian Antarctic stations of
Mawson, Davis and Casey were within or on the edge of the 220 DU contour on 30-31 August, and again on
4 September. The lack of the strong ridge of high ozone in the band immediately south of Australia
between about 40-60S is still evident and quite unusual compared to most previous years.
The period of 5-11 September saw the ozone hole almost completely close, except for a small wedge of
higher total column ozone which is particularly evident on 7 September immediately south of South
America, and proceeded to propagate eastwards to be between the Australian Antarctic stations of
Mawson and Davis by 11 September. The Australian Antarctic stations were within or on the edge of the
220 DU contour for most of the 5-11 September period. During the third week of September the ozone
hole closed completely, with the hole essentially encompassing the whole Antarctic continent during 14-18
September with the vortex appearing to be quite stable. This quite circular (lack of wave activity) ozone
hole has persisted through to 25 September and the 3 Australian Antarctic stations have been inside the
hole (the 220 DU contour) for nearly 2 weeks – this is unusual stability. The lack of an obvious ozone ridge
between Australia and Antarctica has persisted and, what little ridge there is, had weakened such that by
25 September ozone over Macquarie Island was as low as 250 DU.
The stability of the ozone hole continued from 26 September through to 2 October, such that the ozone
hole on 2 October has essentially encompassed all of the Antarctic land area (except the tip of the Antarctic
Peninsula) and considerable areas of the surrounding ocean. The stability has continued (with a few small
“wobbles”) until 11 October, continuing to encompass all of the Antarctic land area (except the tip of the
Antarctic Peninsula) and considerable areas of the surrounding ocean. This seems to be an unprecedented
level of stability. From 12 to 16 October a ridge of higher ozone has formed immediately south of Australia,
which has had the effect of nudging the polar vortex/ozone hole slightly towards South America, which has
result in Casey station being on the edge or just outside of the 220 DU contour. However, overall the ozone
hole is still very stable. During the period of 17-24 October the ozone hole once again became very
symmetrical/circular in shape continuing the very stable and persistent ozone hole this year. All 3
Australian Antarctic stations were inside the hole (the 220 DU contour) during this period, with Casey right
on the edge of the 220 DU contour on 23 & 24 October. The images from 25 October through to 1
November (note that 31 Oct & 1 Nov images from OMI are only partial coverage) show that the ozone hole
has started to become distorted, indicating some wave activity affecting the polar vortex, which is likely to
entrain warmer air from lower latitudes.
The distortion of the polar vortex/ozone hole continued during 2-5 November, such that the tip of South
America was within the ozone hole on 3 & 4 November as the distortion propagated through and all 3 of
the Australian Antarctic stations were outside of the hole on these two days. The distortion of the ozone
hole continued until 11 November, with the image from 12 November showing signs of becoming
symmetrical again. During 6-12 November, the three Australian Antarctic stations were at times in and out
of the ozone hole as the distortion propagated around Antarctica. The overall drop in the ozone minima is
noticeable in the images from 28 Oct through to 12 November shown in Figure 3.
NASA MERRA heat flux and temperature
Heat Flux
The MERRA 45-day mean 45-75S heat fluxes at 50 & 100 hPa are shown in Figure 5. A less negative heat
flux usually results in a colder polar vortex, while a more negative heat flux indicates heat transported
towards the pole (via some meteorological disturbance/wave) and results in a warming of the polar vortex.
The corresponding 60-90S zonal mean temperatures at 50 & 100 hPa are shown in Figure 6, these usually
show an anti-correlation to the heat flux.
During June the 45-75S heat flux at 50 & 100 hPa was in the lower 10-30% of the 1979-2014 range,
indicating a larger amount of heat transported towards the pole than average. During July, at both the 50 &
100 hPa levels, this transitioned to be in the upper 10% range at 50 hPa and 70-90% range at 100 hPa,
indicating a strong reduction in the heat transported towards the pole. By the end of the third week of
August, the 45-75S heat flux at 50 hPa was at the maximum seen for the 1979-2014 range for this time of
year, and at 100 hPa was at the 90th percentile mark of the 1979-2014 range, both continuing to indicate
reduced heat transport towards the pole. During the fourth week of August, the 45-75°S heat flux at 50 hPa
was higher than the maximum seen for the 1979-2014 range for this time of year, and at 100 hPa was in
the highest 10th percentile mark of the 1979-2014 range, both continuing to indicate reduced heat
transport towards the pole. The last few days of August saw the 45-75S heat flux at 50 & 100 hPa remain
in the highest 10th percentile mark of the 1979-2014 range.
The first thirteen days of September saw the 45-75S heat flux at 50 & 100 hPa either exceed the maximum
seen for the 1979-2014 range for this time of year or be in the highest 10th percentile mark of the 19792014 range, both continuing to indicate reduced heat transport towards the pole. However, the forecast
data from 14 to 25 September suggest that this metric will start to drop indicating increased heat flux
towards the pole. Indeed by 25 September the heat flux indicated increased transport of heat towards the
pole, but still in the 10th percentile range (significantly less polar heat transport than the long term
average).
The period of 26 September through to 2 October saw the heat flux stabilise again with the 45-75S heat
flux at both the 50 & 100 hPa levels remaining in the highest 10th percentile mark of the 1979-2014 range,
indicating a stable vortex. The 45-75S heat flux at both the 50 & 100 hPa levels more or less remained in
the highest 10th percentile mark of the 1979-2014 range during 3-16 October, with the forecasted data
predicting it to remain there for the next week or so. Normally by this time of year there is a significant
increase in the amount of heat transported towards the pole, but this is yet to happen for 2015, which may
indicate a persistent ozone hole for 2015. The 45-75S heat flux at both the 50 & 100 hPa levels more or
less remained in the highest 10th percentile mark of the 1979-2014 range during 17-24 October, with the
forecasted data predicting an increase in the heat flux (less heat transported towards the pole) in the next
week. This is certainly indicative that we will see a persistent ozone hole for 2015. By the end of October,
the 45-75S heat flux at both the 50 & 100 hPa levels had shifted into the highest 10-30th percentile range,
indicating slightly more heat transported towards the pole, however it is still significantly higher than the
long-term 1979-2014 mean.
During the first week of November, the 45-75S heat flux at both the 50 & 100 hPa levels continued
tracking within the highest 10-30th percentile range indicating more heat transported towards the pole,
with the forecast data showing this trend continuing. The second week of November saw the 45-75S heat
flux at both the 50 & 100 hPa levels continued tracking within the highest 10-30th percentile range,
however, the forecast data at both of these levels predicts a sharp drop in the heat flux in the coming week
indicating an increase in the heat transported towards the pole.
Temperature
Correspondingly, the 60-90S zonal mean temperatures at 50 & 100 hPa were, overall, similar to the 19792014 average, with some deviations above and below this line in June & July. The beginning of August saw
the 60-90S zonal mean temperatures at both 50 & 100 hPa to be at or just below the previous recorded
lowest minimums for this time of year. By mid-August the temperatures had trended up to once again be
close to the long-term averages. The third week of August saw the 60-90S zonal mean temperatures at
both the 50 & 100 hPa levels drop to be at the lower 10% percent mark of the 1979-2014 range by 21
August, indicating quite cold conditions in the low-to-mid Antarctic stratosphere. The fourth week of
August saw the 60-90S zonal mean temperatures at both the 50 & 100 hPa levels remain quite cold in the
lower 10-30% percent mark of the 1979-2014 range. The last days of August saw the 60-90S zonal mean
temperatures at both the 50 & 100 hPa levels remain quite cold, with the 50 hPa trace remaining in the
lower 10-30% percent mark of the 1979-2014 range, and the 100 hPa trace just inside the lower 30-50%
mark of the 1979-2014 range.
The first thirteen days of September saw 60-90S zonal mean temperatures at both the 50 & 100 hPa levels
remain quite cold either in the lower 10-30% percent mark of the 1979-2014 range or just inside the lower
30-50% mark of the 1979-2014 range. The forecast data from 14 to 25 September indicate that the
temperatures will remain in these ranges for this period. In fact, by 25 September the zonal mean
temperatures at 50 and 100 hPa were at record lows for this time of the year – again a sign of a very stable
(cold) vortex.
During 26 September through to 2 October the zonal mean temperatures at 50 and 100 hPa remained at
record lows for this time of the year – indicating a very stable (cold) vortex. The forecast data suggest that
this will remain the case for at least the next week or two. The period 3-16 October saw the record low
temperatures continue as forecasted. Again this is a sign of a very stable (cold) vortex, and the cold
temperatures are forecasted to continue. During 17-24 October the record low temperatures continued as
forecasted, with the 60-90S zonal mean temperature at 100 hPa recording significantly lower
temperatures than any previous minima during 1979-2014. By the end of October the 60-90S zonal mean
temperatures at both the 50 & 100 hPa levels were still at record low levels, however, the forecast data
indicate that these are likely to increase in the coming week and may no longer be at record levels, but will
still be in the lowest 10th percentile of the 1979-2014 range.
As forecasted last week, during the first week of November the 60-90S zonal mean temperatures at both
the 50 & 100 hPa levels increased quite rapidly, with the 50 hPa trace touching the 30th percentile mark of
the 1979-2014 range & mean by 5 November, while the 100 hPa trace is now just higher than the previous
record minimum for this time of year. The second week of November saw the 60-90S zonal mean
temperature at 50 hPa track along the edge of the 30th percentile mark of the 1979-2014 range, while the
100 hPa trace continued tracking along the lower bound of the 1979-2014 minima. The forecast data
indicate that these trends at the 50 & 100 hPa levels will continue, despite the increase in the forecasted
heat flux.
At 50 hPa, the type 1 PSC (HNO3.3H2O) formation threshold temperature (195 K) was reached in late June,
staying below the threshold until mid-September. At 100 hPa, the threshold temperature was reached
during the second week of July and remain below the threshold on 25 September.
Note a brief description of MERRA is given in the Definitions at the end of this report.
Summary: WMO Antarctic Ozone Bulletin – No. 1, 1 September 2015; No. 2, 21 September 2015; No.
3, 8 October 2015; No. 4, 29 October 2015;
The 2015 (and previous years) WMO Antarctic Ozone
http://www.wmo.int/pages/prog/arep/gaw/ozone/index.html
Bulletins
are
available
from
Temperatures and PSCs
Stratospheric temperatures over Antarctica have been below the PSC type I (nitric acid trihydrate: NAT)
threshold of 194.6 K since 11 May and below the PSC type II threshold of 187.8 K since 3 June.
In late September and early October, a time of the year when temperatures normally increase after the
polar night, the minimum temperature inside the vortex suddenly dropped and on 3 October in reached
181.9 K, which is about 8 K below the 1979-2014 average. After that the minimum temperature has
increased but is still close to the long term (1979-2014) minimum.
The daily minimum temperatures at the 50 hPa level have been below the 1979-2014 average since midApril. On several days in April, May, July and August the 50 hPa minimum temperature was below the 19792014 minimum. Also in September, the minimum temperature has been close to or below the long term
average. The average temperature at 50 hPa over the 60-90S region was oscillating around the long-term
mean until mid-July, after which it has been below the long term mean. In early August it was close to the
1979-2014 minimum. The 60-90°S mean temperature at 50 hPa remained well below the long-term mean
in September and was close to the long-term minimum on some days. In late September and early October,
a time of the year when temperatures normally increase after the polar night, the minimum temperature
inside the vortex suddenly dropped and on 3 October in reached 181.9 K, which is about 8 K below the
1979-2014 average. After that the minimum temperature has increased but is still close to the long term
(1979-2014) minimum at 50 hPa
At 10 hPa, the 60-90S mean temperature has been close to or above the long-term mean on most of the
days during the April to August time period, with a few days below the mean. In late August and the first
half of September, this temperature has been well below the long-term mean. The 60-90°S mean
temperature at 50 hPa remained well below the long-term mean in September and was close to the longterm minimum on some days. On almost every day during October the mean temperatures at 50 and 100
hPa have been below the long term minimum.
Since the onset of NAT temperatures in early May, the NAT area was oscillating around the long term mean
in May and June and remained close to the average in July. In August the NAT area has been well above the
long-term mean on most days. On 5th August the NAT area reached a maximum for the season with 28.2
million km2, which is higher than the maximum reached in recent years. One has to go back to 2009 to find
a higher PSC area maximum (28.4 million km2). Also in September and so far in October, the NAT area has
been well above the long-term mean. Since mid-October, the NAT area has oscillated around the long term
maximum for this time of the year. It is forecast to drop to zero in early November.
The NAT volume was relatively low between late May and early August: it was below the long-term mean
and also below the NAT volume of recent years. During August the NAT volume was similar to that of
recent years (2011, 2013 and 2014) and larger than that of 2012. In September, the NAT volume has been
close to the long-term mean. Since mid-October the NAT volume has oscillated around the long term
maximum
Heat Flux
During May the 45-day mean of the heat flux at 100 hPa was lower than or close to the 1979-2014 average.
In June it was somewhat larger than the long term average. In July and August the heat flux has been
noticeably smaller than the long term mean. In early September the heat flux remained low and on some
days early in the month the heat flux was lower than the long-term minimum. During September the heat
flux increased somewhat but remained comparatively low. During October the heat flux has been smaller
than in 90% of earlier years back to 1979. This is a sign of a stable vortex. However, a wave event is
expected in early November and this will lead to a weakening of the vortex and heating of the stratosphere.
Hydrochloric Acid (HCl)
At the 46.5 hPa level (altitude of ~18.5-19.5 km) the vortex is now almost entirely depleted of hydrochloric
acid (HCl), one of the reservoir gases that can be transformed to active chlorine. The area affected by HCl
removal in 2015 is similar to or larger than in recent years (2010-2014). In the sunlit collar along the vortex
edge there are regions with 2.0-2.1 ppb of active chlorine (chlorine monoxide, ClO), and ozone depletion
has started. Some HCl has come back since the first Bulletin in early September, and along the vortex edge
there are regions with 1.9-2.0 ppb of active chlorine (chlorine monoxide, ClO), and ozone depletion is
already quite advanced. Since Bulletin #2, in large parts of the vortex, and especially at the lower levels at
altitudes below 46 hPa, HCl is reappearing and active chlorine is less abundant than two weeks ago. At
higher levels, around 30-35 hPa, there is still a core of the vortex with very low HCl and more than 3 ppb of
active chlorine. By late October, the whole vortex is now filled with hydrochloric acid (HCl) and essentially
all the active chlorine has disappeared. This means that ozone destruction has come to a halt.
Satellite Observations
Satellite observations show that the area where total ozone is less than 220 DU (‘ozone hole area’) has
been significantly above zero since 18 August. This is a relatively late onset of ozone depletion. The ozone
hole area on 27 August was approx. 5.1 million km2, about half the long-term average. The date of the
onset of ozone depletion varies considerably from one year to the next, depending on the position of the
polar vortex and availability of sunshine after the polar night. During September ozone depletion picked up,
and the ozone hole area reached 25.5 million km2 on 19 September. This is larger than the maxima reached
for any of the years during the 2009-2014 time period. During October, the ozone hole area reached 26.9
million km2 on 2 October according to the analysis from KNMI, which is based on data from the GOME-2
satellite instrument. Analysis by NASA, based on data from the OMI satellite instrument gives a maximum
ozone hole area for 2015 of 28.2 million km2, also on 2 October. This is the largest maxima reached since
2006. Averaging the ozone hole area over various time periods also shows that the 2015 ozone hole is one
of the largest on record.
In 2015, the vortex has been relatively stable and concentric around the South Pole. This can explain the
late onset of ozone depletion. Its area has also been comparatively large, and this can explain the relatively
large area of the ozone hole.
As the sun returns to Antarctica after the polar night, ozone destruction will speed up. It is still too early to
give a definitive statement about the development of this year’s ozone hole and the degree of ozone loss
that will occur. This will, to a large extent, depend on the meteorological conditions. However, the
temperature conditions and the extent of polar stratospheric clouds so far indicate that the degree of
ozone loss in 2015 will be similar to that observed in 2014 and 2013 and probably somewhat larger than in
2010 and 2012.
As of October, the sun is now back everywhere in Antarctica and ozone destruction will continue as long as
there is active chlorine available. In terms of ozone hole area, 2015 seems to surpass all recent years back
to and including 2009. The ozone mass deficit is so far comparable to that experienced in 2012 and 2013
but still lagging behind in comparison to many of the other years since 2009. The ozone mass deficit usually
reaches a maximum in early October, so it is still too early to give a definitive statement about its maximum
value this year.
Satellite Instrumentation
OMI
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, have been utilized again this year in our
weekly ozone hole reports. OMI continues the NASA TOMS satellite record for total ozone and other
atmospheric parameters related to ozone chemistry and climate.
On 19 April 2012 a reprocessed version of the complete (to date) OMI Level 3 gridded data was released.
This is a result of a post-processing of the L1B data due to changed OMI row anomaly behaviour (see
below) and consequently followed by a re-processing of all the L2 and higher data. These new data have
now been reprocessed by CSIRO, which has resulted in small changes in the ozone hole metrics we
calculate, and as such, these metrics may be slightly different for previous years for OMI data (2005-2011).
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 and exhibits a more dynamic
behaviour than before, 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. It is now thought that the row
anomaly problem may have started and developed gradually since as early as mid-2006. Despite various
attempts, it turned out that due to the complex nature of the row anomaly it is not possible to correct the
L1B data with sufficient accuracy (≤ 1%) for the errors caused by the row anomaly, which has ultimately
resulted in the affected data being flagged and removed from higher level data products (such as the daily
averaged global gridded level 3 data used here for the images and metrics calculations). However, once the
polar night reduces enough then this should not be 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.
OMPS
OMPS (Ozone Mapping and Profiler Suite) is a new ozone instrument on the Suomi National Polar-orbiting
Partnership satellite (Suomi NPP), which was launched on 28 October 2011 and placed into a sunsynchronous orbit 824 km above the Earth. The partnership is between NASA, NOAA and DoD (Department
of Defense), see http://npp.gsfc.nasa.gov/ for more details. OMPS will continue the US program for
monitoring the Earth's ozone layer using advanced hyperspectral instruments that measure sunlight in the
ultraviolet and visible, backscattered from the Earth's atmosphere, and will contribute to observing the
recovery of the ozone layer in coming years. For the 2014 ozone hole season, we will also be using the
OMPS total column ozone data by producing metrics from both OMI and OMPS Level 3 global gridded daily
total ozone column products from NASA, and present both sets of results for comparison. NOTE that NASA
receive the raw OMPS data from NOAA, and due to some operational delays, NASA have decided to delay
the processing of data by 96 hours (4 days) from the time they obtain the first raw data for a given day. As a
result, the OMPS Level 3 global gridded daily total ozone column products provided by NASA run 4-5 days
behind the current day.
Figure 1: Ozone hole area (top panel) and estimated daily ozone deficit (bottom panel) based on OMI (data
up to 12 November 2015) and OMPS (data up to 7 November 2015) satellite data.
Figure 2: Ozone hole depth (top panel) and average ozone amount within the ozone hole (bottom panel)
based on OMI (data up to 12 November 2015) and OMPS (data up to 7 November 2015) satellite data.
Figure 3: OMI ozone hole images for 28 October-12 November 2015; the ozone hole boundary is indicated
by the red 220 DU contour line. The Australian Antarctic (Mawson, Davis and Casey) and Macquarie Island
stations are shown as green plus symbols. The white stripes are bad/missing data due to a physical
obstruction in the OMI instrument field of view.
Figure 4: OMPS ozone hole images for 23 October-7 November 2015; the ozone hole boundary is indicated
by the red 220 DU contour line. The Australian Antarctic (Mawson, Davis and Casey) and Macquarie Island
stations are shown as green plus symbols. Note that due to operational reasons, the OMPS Level 3 global
gridded daily total ozone column products provided by NASA run 4-5 days behind the current day.
Figure 5: 45-day mean 45S-75S eddy heat flux at 50 & 100 hPa. Images courtesy of NASA GSFC,
downloaded 16 November 2015, data through to 25 November 2015 (data starting 2015-09-30 are from
GEOS5FP; 2015-11-14 are forecasts):
http://ozonewatch.gsfc.nasa.gov/meteorology/flux_2015_MERRA_SH.html
Figure 6: 60S-90S zonal mean temperature at 50 & 100 hPa. Images courtesy of NASA GSFC, downloaded
16 November 2015, data through to 23 November 2015 (data starting 2015-09-30 are from GEOS5FP; 201511-14 are forecasts):
http://ozonewatch.gsfc.nasa.gov/meteorology/temp_2015_MERRA_SH.html
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.
MERRA: is a NASA reanalysis for the satellite era using a major new version of the Goddard Earth Observing
System Data Assimilation System Version 5 (GEOS-5). The project focuses on historical analyses of the
hydrological cycle in a broad range of weather and climate time scales. It places modern observing systems
(such as EOS suite of observations) in a climate context. Since these data are from a reanalysis, they are not
up-to-date. So, NASA supplement with the GEOS-5 FP data that are also produced by the GEOS-5 model in
near real time. These products are produced by the NASA Global Modeling and Assimilation Office (GMAO).
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 (< -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.
TOMS, OMI & OMPS: the Total Ozone Mapping Spectrometer (TOMS), Ozone Monitoring Instrument (OMI),
and Ozone Mapping and Profiler Suite (OMPS) are satellite borne instruments that measure 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. The OMPS Level 3 data used in this report were created from a
research dataset developed by NASA's NPP Ozone Science Team using nadir measurements from SuomiNPP's Ozone Mapping and Profiler Suite(OMPS). All data were downloaded from
ftp://jwocky.gsfc.nasa.gov/pub.