The 2017 Antarctic Ozone Hole Summary: Report #3, Sunday 10 September 2017
The 2017 Antarctic Ozone Hole Summary: Report #3, Sunday10September2017
Paul Krummel and Paul Fraser
CSIRO Oceans and Atmosphere, Climate Science Centre
Aspendale, Victoria
Summary
For the 2017 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). Unless otherwise stated, the metrics quoted in this report are calculated from the OMPS data products. Please note the OMPS data used in this report are the Level 3 data created from Version 2 (V2) of the Nadir Mapper (NM) dataset from the Suomi National Polar-orbiting Partnership satellite.
August
The first excursions below 220 DU of the ozone minima occurred in early August around the fringes of the polar night, and since 4 August have remained below 220 DU, dropping to 176 DU on 10 August before recovering to 202 DU by 13 August. During the first two weeks of August the ozone hole area peaked at 3.9 million km2 on 8 August before reducing to 3.3 million km2 by 13 August. The forecasts from Merra2 of the 50 & 100 hPa temperatures and heat fluxes are indicating a significant warming event in the coming week, which may see the ozone levels rise above 220 DU again. The forecast warming event did occur, with the 45-75S heat flux at 50 & 100 hPa dipping to low values (more heat transported towards the hole) on 27-28 August, and the corresponding 60-90S zonal mean temperatures at 50 & 100hPa increasing to be in the highest 10% of the 1979-2016 range through the second half of August. This resulted in the ozone hole area and deficit dropping sharply, while the ozone minima metrics increased, during the fourth week of August. However, by the end of August and early September, the ozone hole area increased rapidly to be at 12.5 million km2 by 2 September, while the ozone deficit increased to about 4 million tonnes, and the ozone minima dropped to 184 DU. From 29 August onwards, the ozone hole images clearly show that thehole is forming in earnest and it is expect that the 220 DU contour will be completely closed within the next week.
September
The first week of September saw the ozone hole continue to get larger, with the area reaching 18.2 million km2, the daily ozone deficit increasing to 8.3 million tonnes and the minima dropping to 159 DU by 8 September. The 45-75S heat flux and 60-90S zonal mean temperatures remained relatively stable during the first week of September, however, the forecast data are suggesting a sudden strong warming event over the coming week, which is reflected as an increase in the 60-90S zonal mean temperatures into the top 10th percentile of the 1979-2016 range. This will likely have a considerable impact on the ozone hole metrics over the next week.
The 2017 ozone hole
Ozone hole area
The top panel of Figure 1 shows that during the first two weeks of August the ozone hole area peaked at 3.9 million km2 on 8 August before reducing to 3.3 million km2 by 13 August.The second half of August through to early September saw the ozone hole area initially peak at 6.1 million km2 on 15 August, then drop back to 1.7 million km2 on 22 August before increasing rapidly to be at about 12.5 million km2 by 2 September. This is similar in size to the 2012, 2014 & 2015 ozone holes for the same time of year.From 26 August onwards there is a noticeable difference between the ozone hole area calculated from OMPS and OMI – on average the ozone hole area calculated from OMI is about 30% lower than the OMPS equivalent. This difference is expected to decrease once the ozone hole fully closed and the polar night reduced.
The first week of September saw the ozone hole area continue to increase, reaching 18.2 million km2 by 8 September.
Ozone deficit
The bottom panel of Figure 1 shows that by mid-August there were small levels of estimated daily ozone deficitcorresponding to the above mentioned ozone hole areas. The estimated daily ozone deficit reached 1.3 million tonnes on 10 August before dropping back to < 0.5 million tonnes on 13 August.Similar to the ozone hole area, the second half of August through to early September saw the estimated daily ozone deficit peak at 2.4 million tonnes on 15 August, then drop back to 0.3 million tonnes on 22 August before increasing to be at about 4 million tonnes by 2 September.
During the first week of September, the daily ozone deficit increased to 8.3 million tonnes by 8 September, which is on the lower side for this time of year compared with the past 5 ozone holes.
Ozone hole minima
The first excursions below 220 DU occurred in early August around the fringes of the polar night (see Figures 3 & 4), and since 4 August have remained below 220 DU, dropping to 176 DU on 10 August before recovering to 202 DU by 13 August.This metric can be highly variable at this time of year, but this variability is expected to reduce in the next two to three weeks as the polar night reduces and the ozone hole fully forms. During the second half of August and early September the ozone hole minima continued to show variability, dropping to 175 DU on 17 August before rising again to 202 DU on 22 August. By 2 September the ozone hole minima had dropped again to 184 DU with indications that the variability in this metric has reduced considerably.
The ozone minima dropped to 159 DU by 8 September, which is middle of the pack compared with the last 5 ozone holes for this time of year.
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 a similar pattern to that of the ozone hole minima. The average ozone amount dropped to 199 DU on 10 August, and by 13 August had risen to 214 DU.Following this, the average ozone amount fluctuated between 201 DU and 214 DU, and ended at 205 DU on 2 September.
After the first week of September, the average ozone amount in the hole had dropped to 199 DU, and similar to the ozone deficit, this is on the higher side for this time of year compared with the past 5 ozone holes.
Total column ozone images
The most recent 16 days of total column ozone ‘images’ over Australia and Antarctica from OMI are shown in Figure 3 and from OMPS are shown in Figure 4.
From early August onwards, the ozone hole can be seen forming in several areas around the polar night. By the end of the second week of August the Antarctic polar night still covered most of Antarctica. The strong ridge of high ozone in the band immediately south of Australia between about 40-60S is present again in 2017.Figure 4 shows the ozone hole images from 18 August through to 2 September and what can be clearly seen is the ozone hole forming in earnest from 29 August onwards; it is expected that the 220 DU contour shown in red will be completely closed within the next week.
From 3-8 September the ozone hole can be seen to continue to form, with the 220 DU contour now almost completely enclosed. During this period, the 3 Australian Antarctic stations were outside of the ozone hole, and Macquarie Island remained under a ridge of high ozone. On 8 September, the tip of South America was just touching the edge of the ozone hole.
NASA MERRA heat flux and temperature
The MERRA 45-day mean 45-75S heat fluxes at 50 & 100hPa 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 60-90S zonal mean temperatures at 50100hPa are shown in Figure 6, these usually show an anti-correlation to the heat flux.
At 50 hPa, the type 1 PSC (HNO3.3H2O) formation threshold temperature (195K) was reached in mid- to late June. At 100 hPa, the threshold temperature was reached in early July.
May, June, July
During mid-May to mid-Junethe45-75S heat flux at 50 & 100 hPa was higher than compared to the 1979-2016 range, indicating lessheat transported towards the pole. Correspondingly, the 60-90S zonal mean temperatures at 50 & 100hPa werelower than average being in the lower 10-30th percentile or lowest 10 percentile of the 1979-2016 range. From mid-June to end of July, the 45-75S heat flux at 50hPa& 100 hPa shifted down to be at the 30thpercentile mark of the 1979-2016 range, indicating more heat transport towards the pole. Interestingly, the 60-90S zonal mean temperatures at 50 & 100hPa from mid-June to the end of July essentially remained in the lowest 30 percentile range.
August
The first two weeks of August saw the 45-75S heat flux at 50 & 100 hParemain at approximately the 30thpercentile mark of the 1979-2016 range. The corresponding 60-90S zonal mean temperatures at 50 & 100hPa during the first two weeks of August increased to close to the 1979-2016 average, before increasing to be in the upper 70-90th percentile of the 1979-2016 range, indicating the beginning of a warming event. The forecasts from Merra2 of the 50 & 100 hPa temperatures and heat fluxes are indicating a significant warming event in the coming week, which may see the ozone levels rise above 220 DU again. The forecast warming event did occur, with the 45-75S heat flux at 50 & 100 hPa dipping to low values (more heat transported towards the hole) on 27-28 August, both levels were in the lowest 10% of the 1979-2016 range, with the 50 hPa trace briefly dropping below the previous minimum value. Following this, the heat flux at both levels increased again to be in the 10-30% mark of the 1979-2016 range. Correspondingly, the 60-90S zonal mean temperatures at 50 & 100hPa during the last half of August increased to be in the highest 10% of the 1979-2016 range. By early September the temperatures at the both 50 & 100 hPa had dropped sharply to be back in the 70-90% mark of the 1979-2016 range. The forecast suggests that the temperatures at the both 50 & 100 hPa will remain relatively constant over the coming week.
The first week of September saw the 45-75S heat flux at 50 & 100 hPa remain in the 10-30% mark of the 1979-2016 range, while the60-90S zonal mean temperatures at the both 50 & 100 hPa remained in the 70-90% mark of the 1979-2016 range. The 45-75S heat flux forecast data are suggesting a sudden strong warming event over the coming week, which is reflected as an increase in the 60-90S zonal mean temperatures into the top 10th percentile of the 1979-2016 range.
Figure 1:Ozone holearea(top panel) and estimated daily ozone deficit (bottom panel) based on OMI(data up to 8September 2017) and OMPS (data up to 8September 2017) 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 8September 2017) and OMPS (data up to 8September 2017) satellite data.
Figure 3: OMI ozone hole images for 24August– 08 September 2017; 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 24August – 08 September2017; 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.
Figure 5: MERRA2 45-day mean 45S-75S eddy heat flux at 50 & 100hPa. Images courtesy of NASA GSFC, downloaded 10September 2017, data through to 19September 2017(data starting2017-08-01 are from GEOS5FP;2017-09-09onwards are forecasts):
Figure 6: MERRA2 60S-90S zonal mean temperature at 50 & 100hPa. Images courtesy of NASA GSFC, downloaded 10September 2017, data through to 17September 2017(data starting 2017-08-01 are from GEOS5FP; 2017-09-09onwards are forecasts):
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 sun-synchronous orbit 824 km above the Earth. The partnership is between NASA, NOAA and DoD (Department of Defense), see 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 2017 ozone hole season, we will be using the OMPS total column ozone data and will be 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.The OMPS data used in this report are the Level 3 data created from Version 2 (V2) of the Nadir Mapper (NM) dataset from Suomi-NPP's Ozone Mapping and Profiler Suite (OMPS).
Archive of the Weekly Reports
The weekly Antarctic Ozone Hole reports for the 2017ozone hole season are available from the Department of the Environment and Energy web page here:
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).
MERRA2: MERRA2 was introduced to replace the original MERRA dataset because of the advances made in the assimilation system that enable assimilation of modern hyperspectral radiance and microwave observations, along with GPS-Radio Occultation datasets. It also uses NASA ozone observations after 2005. Additional advances in both the GEOS-5 model and the GSI assimilation system are included in MERRA-2.