Paul Krummel and Paul Fraser
CSIRO Oceans and Atmosphere
Aspendale, Victoria
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.
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 km 2 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.
The last few days of August, beginning of September saw the ozone hole area increase rapidly to be approximately 15 million km 2 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 km 2 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 km 2 , 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 km 2 by 24 September. This may be the maximum area this year and is about the
9 th 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.
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 km 2 on 2 October, now the 4 th 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 km 2 ) and 2003 (28.4 million km 2 ). 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.

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 km 2 . The ozone hole area continued to grow during the fourth week of August reaching 6.3 million km 2 on 26 August before dropping back to just under 5 million km 2 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 km 2 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 km 2 on 7 September before dropping back to 18.7 million km 2 on 9 September and increasing again to 21.5 million km 2 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 km 2 on 18 September and 26.4 million km 2 on 24 September, which is now the 9 th largest hole in terms of daily area, just below the 2001 hole (which was also 26.4 million km 2 ). 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 km 2 on 2 October, now the 4 th 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 km 2 ) and 2003 (28.4 million km 2 ). 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 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.
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 longterm 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 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.
Total column ozone data over Australia and Antarctica for 26 September – 5 October 2015 from OMI are shown in Figure 3 and for 19 – 28 September 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 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 90 th 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 10 th 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 10 th 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 10 th percentile mark of the 1979-
2014 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 10 th 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 10 th percentile mark of the 1979-2014 range, indicating a stable vortex.
Correspondingly, the 60-90

S zonal mean temperatures at 50 & 100 hPa were, overall, similar to the 1979-
2014 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.
At 50 hPa, the type 1 PSC (HNO
3
.3H
2
O) 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.
No. 1, 1 September 2015
The 2015 (and previous years) WMO Antarctic Ozone Bulletins are available from http://www.wmo.int/pages/prog/arep/gaw/ozone/index.html
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. The daily minimum temperatures at the 50 hPa level have been below the 1979-2014 average since mid-April. On several days in April, May, July and August the 50 hPa minimum temperature was below the 1979-2014 minimum. 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. 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.
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 5 th August the NAT area reached a maximum for the season with 28.2 million km 2 , 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 km 2 ).
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.
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. This is an indication of a stable vortex.
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.
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 km 2 , 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. In 2015, the vortex has been relatively stable and concentric around the South Pole. This can explain the late onset of ozone depletion.
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.
Summary: WMO Antarctic Ozone Bulletin – No. 2, 21 September 2015
The 2015 (and previous years) WMO Antarctic Ozone Bulletins are available from http://www.wmo.int/pages/prog/arep/gaw/ozone/index.html
Temperatures and PSCs
Stratospheric temperatures over Antarctica have been below the PSC type I threshold of 194.6 K since 11
May and below the PSC type II threshold of 187.8 K since 3 June. The daily minimum temperatures at the
50 hPa level have been below the 1979-2014 average since mid-April. On several days in April, May, July and August the 50 hPa minimum temperature was below the 1979-2014 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. Also in September this temperature has remained well below the long-term mean and on some days it has even been close to the long-term minimum.
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. 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 km 2 , 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 km 2 ). So far in September, the NAT area has also been well above the long-term mean.
The NAT volume was relatively low between late May and early August: it was below the long-term mean and also below the NAT area of recent years. During August the NAT volume was similar to that of recent years (2011, 2013 and 2014) and superior to that of 2012. In September, the NAT volume has close to the long-term mean.
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. This is an indication of a stable vortex.
Hydrochloric Acid (HCl)
At the 46.5 hPa level (altitude of ~18.5-19.5 km) the vortex is still almost entirely depleted of hydrochloric acid (HCl), one of the reservoir gases that can be transformed to active chlorine. Some HCl has come back since the first Bulletin in early September, though. The area affected by HCl removal in 2015 is similar to or larger than in recent years (2010-2014). 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.
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. During
September ozone depletion picked up, and the ozone hole area reached 25.5 million km 2 on 19 September.
This is larger than the maxima reached for any of the years during the 2009-2014 time period. 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.
Balloon Sonde Data
Measurements with ground based instruments and with balloon sondes show clear signs of ozone depletion most sites. In this issue data are reported from the following stations: Arrival Heights, Belgrano,
Davis, Dôme Concordia, Dumont d’Urville, Halley, Kerguelen, Macquarie Island, Marambio, Mirny,
Neumayer, Novolazarevskaya, Rothera, South Pole, Syowa, Ushuaia, Vernadsky and Zhongshan.
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.

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 2 October 2015) and OMPS (data up to 28 September 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 2 October 2015) and OMPS (data up to 28 September 2015) satellite data.

Figure 3: OMI ozone hole images for 17 September – 2 October 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 area over Antarctica is missing data and indicates the approximate extent of the polar night. The OMI instrument requires solar radiation to the earth’s surface in order to measure the column ozone abundance. 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 13 – 28 September 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 area over Antarctica is missing data and indicates the approximate extent of the polar night. The OMPS instrument requires solar radiation to the earth’s surface in order to measure the column ozone abundance. 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 5 October 2015, data through to 14 October 2015 (data starting 2015-10-03 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
5 October 2015, data through to 12 October 2015 (data starting 2015-10-03 are forecasts): http://ozonewatch.gsfc.nasa.gov/meteorology/temp_2015_MERRA_SH.html

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 O
3
; 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 Suomi-
NPP's Ozone Mapping and Profiler Suite(OMPS). All data were downloaded from ftp://jwocky.gsfc.nasa.gov/pub .