MACC-III Deliverable D23.3
Report on 2014 Antarctic ozone hole
studies
Date: March 2015
Lead Beneficiary: BIRA-IASB
Nature: R
Dissemination level: PU
Grant agreement n°633080
File: MACCIII_GRG_DEL_D_23.3_AntOzoneHole2014
Work-package
GRG.7
Deliverable
D23.3
Title
Report on 2014 Antarctic ozone hole studies
Nature
O
Dissemination
PU
Lead Beneficiary
BIRA_IASB (#21)
Date
09 March 2015
Status
Final
Authors
E. Botek, S. Chabrillat, Y. Christophe (BIRA-IASB)
Editor
M. Schultz (FZJ)
Contact
[email protected]
This document has been produced in the context of the MACC-III project (Monitoring Atmospheric
Composition and Climate - III). The research leading to these results has received funding from the European
Community's Horizon 2020 Programme under grant agreement n° 633080. All information in this document
is provided "as is" and no guarantee or warranty is given that the information is fit for any particular
purpose. The user thereof uses the information at its sole risk and liability. For the avoidance of all doubts,
the European Commission has no liability in respect of this document, which is merely representing the
authors view.
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Summary
Every year above the Antarctic, a large region of the stratosphere is severely depleted in ozone. This
“ozone hole” episode typically lasts from August/September until October/November and is due to a
combination of chemical causes (presence of ozone-depleting anthropogenic species) and enabling
meteorological factors (strong and stable polar vortex during Summer and Fall). As stated in the
Executive Summary of the 2010 edition of the WMO/UNEP Scientific Assessment of Ozone
Depletion, severe Antarctic ozone holes are expected to form during the next couple of decades
before a gradual recovery will occur thanks to the international regulations adopted under the
Montreal Protocol. Due to the meteorological variability, there are large interannual variations in
the starting and ending dates of Antarctic ozone depletion, as well as in the size of the impacted
area and in the intensity of ozone depletion. It is important to disentangle this interannual variability
from longer-term trends. Hence monitoring the Antarctic ozone hole is an important task for the
Global Atmosphere Watch (GAW) programme of the World Meteorological Organization (WMO).
Thanks to its Near-Real Time Chemical Data Assimilation systems, The MACC stratospheric ozone
service has participated to this monitoring since 2010. This report highlights the contribution of the
MACC analyses products (MACC_osuite, BASCOE and TM3DAM) to the latest Antarctic Ozone
Bulletin issued by WMO/GAW, and delivers some additional results obtained in MACC w.r.t. the
monitoring of the Antarctic ozone hole in 2014.
Overall the 2014 ozone hole was quite typical until mid-October and decreased relatively quickly
afterwards, although not as quickly as during the two previous years. During Austral Fall 2014, the
ozone hole (here defined as the area where total ozone is less than 220 DU) appeared on 6 August
according to satellite observations, and reached a maximum on 11 September with 24.1 million
square kilometres. A second maximum on 1 October showed an ozone hole area of 23.9 million
square kilometres. The ozone mass deficit reached a maximum of 30.1 megatonnes on the 1st of
October. This is more than the 24.6 megatonnes reached in 2013 and the 21.6 megatonnes reached
in 2012, but less than the 36.8 megatonnes reached in 2011. During the first half of the ozone hole
season (i.e. until mid-October), the 2014 ozone hole was very similar to the one of 2013 and
significantly larger than the one of 2012. The average temperature at 50 hPa over the 60-90°S was
close to the 1979-2013 mean during most of the winter and spring periods. After early October the
60-90°S average temperature was somewhat above the long term mean. In July and August the heat
flux was noticeably larger than the long term mean. Even though this was an indication of a
relatively unstable vortex, during September and October the flux remained close to the long-term
mean. The ozone hole area decreased markedly at the beginning of November, i.e. earlier than in
any of the years 2007-2011 but one month later than in 2012 and 2013 when the polar vortex
disappeared exceptionally early.
Measurements with ground based instruments and with balloon sondes showed clear signs of ozone
depletion at most sites. This report highlights the measurements taken at the South Pole and at the
Ushuaia station in Argentina. The South Pole was chosen for its central location, and Ushuaia (which
is typically at the edge of the polar vortex) was selected, because the MACC stratospheric ozone
service helped the station operators to plan and interpret their ozone soundings during the 2014
ozone hole season. Compared to a typical episode, in 2014 the polar vortex was shifted towards the
Atlantic sector and South America during long periods. This led to low ozone over stations reaching
as far north as Ushuaia. Stations facing the Pacific sector were outside of the vortex for long periods
and experienced large total ozone values.
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Contents
1
Introduction.............................................................................................................. 5
2
Metereological conditions in 2014 compared with previous years ............................. 6
3
Chemical activation of the vortex .............................................................................. 9
3.1
MACC analyses of ozone-depleting substances .................................................................................... 9
3.2
Exploitation in the Antarctic Ozone Bulletin by WMO GAW ........................................................ 11
4
Ozone depletion ..................................................................................................... 12
4.1
Analyses of satellite observations........................................................................................................... 12
4.2
Ozone hole area and mass deficit ............................................................................................................ 16
4.3
Ground-based and balloon observations ............................................................................................. 17
5
References .............................................................................................................. 20
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1
Introduction
The Antarctic polar vortex is a large low-pressure system where high velocity winds (polar
jet) in the stratosphere surround the Antarctic continent. The region poleward of the polar
jet includes the lowest temperatures and the largest ozone losses that occur anywhere in
the world. During early August, information on meteorological parameters and
measurements from ground stations, balloon sondes and satellites of ozone and other
constituents can provide some insight into the development of the polar vortex and, hence,
of the ozone hole later in the season. Low temperatures lead to the formation of clouds in
the stratosphere, so-called polar stratospheric clouds (PSCs).
Under normal conditions there are no clouds in the stratosphere because the amount of
water is very low. However, when the temperature drops below -78°C, clouds that consist of
a mixture of water and nitric acid (HNO3) start to form (PSCs of type I). On the surface of
particles in the cloud, chemical reactions occur that transform passive and innocuous
halogen compounds (e.g. HCl and HBr) into active chlorine and bromine species (e.g. ClO
and BrO). These active forms cause rapid ozone loss in sunlit conditions through catalytic
cycles where one molecule of ClO can destroy thousands of ozone molecules before it is
passivated through the reaction with nitrogen dioxide (NO2). When temperatures drop
below -85°C, clouds that consist of pure water ice will form (PSCs of type II). Particles in both
cloud types can grow so large and fall out of the stratosphere sweeping HNO3 away, which is
a reservoir that liberates NO2 under sunlit conditions. If NO2 is physically removed from the
stratosphere (denitrification), active chlorine and bromine can destroy many more ozone
molecules before they are passivated. The formation of ice clouds will lead to more severe
ozone loss than that caused by PSC type I alone since halogen species are more effectively
activated on the surfaces of the larger ice particles.
The situation with annually recurring Antarctic ozone holes is expected to continue as long
as the stratosphere contains an excess of ozone depleting substances. As stated in the
Executive Summary of the 2010 edition of the WMO/UNEP Scientific Assessment of Ozone
Depletion, severe Antarctic ozone holes are expected to form during the next couple of
decades before a gradual recovery will occur thanks to the international regulations
adopted under the Montreal Protocol. But due to the meteorological variability, there can
be large interannual variations in the starting and ending dates of Antarctic ozone depletion,
as well as in the size of the impacted area and in the intensity of ozone depletion. This
report intends to disentangle this interannual variability from longer-term trends. It is based
on data provided by the MACC stratospheric ozone service (MACC_osuite, BASCOE,
TM3DAM) and on the latest Antarctic ozone Bulletin, which uses the MACC datasets
extensively. See Lefever et al., 2015 (and refs. therein) for an exhaustive description of the
mentioned MACC products in simulating ozone.
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2
Metereological conditions in 2014 compared with previous years
Temperatures and PSC NAT volume
Figure 1 (left) shows temperatures averaged over the 60-90°S region at 50 hPa. The 2014 average
temperature has been close to the 1979-2013 mean until early October 2014, when the Southern
polar cap became somewhat warmer than the long-term mean for this period of the year.
Since 27 June, temperatures low enough for nitric acid trihydrate (NAT or PSC type I) formation have
covered an area of more than 20 million km2 at the 460 K isentropic level. The daily progression of
the NAT volume in 2014 is shown on Figure 1 (right) in comparison to recent winters and long-term
statistics. Since the onset of PSCs in early May until mid July, the NAT volume was close to and (some
days above) the 1979-2013 average. The NAT volume has in 2014 followed the evolution of 2013
quite closely. The volume with temperatures low enough for the existence of PSCs is directly linked
to the amount of ozone loss that will occur later in the season, but the degree of ozone loss also
depends on other factors, such as the amount of water vapour and HNO3.
Figure 1: Time series of temperature averaged over the region south of 60°S at the 50 hPa level (left) and of
the volume where temperatures are low enough for the formation of nitric acid trihydrate (NAT) PSCs. The red
curves show 2014 values. The two thin black lines show the maximum and minimum temperature/PSC area
during the 1979-2013 time period for each date.
Credits: left, Ozonewatch web site at NASA; right, WMO GAW based on data from NOAA/NCEP.
Vortex stability and Ozone column
The longitudinally averaged heat flux between 45°S and 75°S is an indication of the degree of
perturbation of the stratosphere. During May and June the 45-day mean of the heat flux was lower
than or close to the 1979-2013 average. In July and August the heat flux was noticeably larger than
the long term mean. This indicates a relatively unstable vortex. During September it was close to the
long term mean. In October it has rapidly increased, even to lower values than the long term mean.
From November a decrease begun and it joined the average line. The development of the heat flux is
shown in Figure 2.
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Figure 2: Time series of the meridional heat flux averaged over the 45-75°S region. The red curve shows data
for 2014 (updated until 13 October). Please note that a large negative number means a large heat flux. Values
closer to zero means a small heat flux. Data from NOAA/NCEP downloaded from the Ozonewatch web site at
NASA.
Figure 3: Maps of potential vorticity (PV) on 13 Ocober for years 2009-2014at the isentropic level of 475 K, .
This level corresponds to approximately 19 km altitude. The data originates from the ECMWF and are made
available by the Norwegian Institute for Air Research (NILU) through a project funded by the European Space
Agency (ESA). Figure copied from the WMO/GAW Antarctic Ozone Bulletin No 4/2014: the plots were
produced at WMO.
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Whereas the vortex was well centred over the South Pole on this date in 2009 and 2010,
one can see that in 2013 and 2014 it was shifted towards the Atlantic Ocean and South
America. One can also see (Figure 3) that the absolute value of the PV was larger (more
negative and more red) in 2009-2011 than in 2012-2014. This is an indication that the vortex
was more stable in mid October of 2009, 2010 and 2011 than in 2012, 2013 and 2014.
Figure 4 illustrates in more detail the variation and declination of the 2014 vortex till 24
November through potential vorticity maps generated by our stratospheric service from
ECMWF data.
Figure 4: Maps of potential vorticity (PV) at the isentropic level of 485 K. The data originates from the ECMWF
and the plots are produced by the MACC stratospheric ozone service: http://www.copernicusstratosphere.eu/.
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3
3.1
Chemical activation of the vortex
MACC analyses of ozone-depleting substances
As part of the MACC stratospheric ozone service, the BASCOE Data Assimilation System (Errera and
Ménard, 2012) delivers global analyses of N2O, HNO3, H2O, HCL and ClO as observed by Aura-MLS
(offline retrievals v3.3). Figures 5 and 6 show the time evolution of the mixing ratio of these species,
averaged over 60°S-90°s and interpolated at 20km altitude, during the Antarctic 2014 ozone hole
episode.
Figure 5: Volume mixing ratios of N2O (top), H2O (middle) and HNO3 (bottom), at 20 km altitude, averaged
over the Antarctic latitude band (60°S-90°S) from June to December 2014. Black dots: daily means of MLS
observations Solid line
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Figure 6: Volume mixing ratios (ppbv) of HCl (top) and ClO (bottom), at 20 km altitude, averaged over the
Antarctic latitude band (60°S-90°S) from June to December 2014.
The decrease of N2O, which is a long-lived tracer, illustrates the downdraft of N2O-poor air masses
and their containment within the vortex. This advection process also partly explains the observed
dehydration and denitrification, which take place more quickly in the analyses than in the
assimilated observations due to the raw parameterization of PSC in BASCOE which prevents
complete assimilation of H2O and HNO3 observations in this region.
Figure 6 shows that the evolution of the chlorine reservoir (HCl) and ozone-depleting radical (ClO) is
relatively well represented in the BASCOE analyses. Chlorine activation built up gradually until midSeptember and ended quickly during the three next weeks.
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3.2
Exploitation in the Antarctic Ozone Bulletin by WMO GAW
Figure 7 is copied from the WMO/GAW Antarctic Ozone Bulletin No 4/2014. Using the BASCOE
analyses delivered by MACC, it shows maps at 46 hPa of HCl, ClOx (=ClO+2*Cl2O2) and ozone over
the time period from 1 July until 11 October. One can see how HCl (first row) is being depleted as it
is being converted on the PSC particles. By 1 August essentially the whole vortex is entirely devoid of
HCl. Between 8 and 23 September, HCl has partly recovered as the amounts of polar stratospheric
clouds has been reduced. On 1 October there is just a small area left with depleted HCl and by 11
October HCl is completely recovered. The middle row shows the sum of ClO and Cl2O2. This is an
indication of the total amount of active chlorine. ClO dimerises in darkness, but is rapidly cracked in
the presence of daylight. On 1 July there is elevated amounts active chlorine inside the vortex and
the concentration increases gradually as the processing on the PSCs continues. From 22 August to 8
September the maximum concentration of active chlorine has gone down a bit, but the vortex is
more evenly filled with active chlorine on 8 September. From 8 to 23 September the amount of
active chlorine is reduced significantly, but there is still active chlorine remaining and that continues
to destroy ozone. By 1 October the amount of active chlorine is greatly reduced and on 11 October
there is no active chlorine left.
The mixing ratio of ozone (lower row) shows quite a dramatic development over the course of the
time period shown here. On 1 July there is yet no sign of ozone depletion. By 22 August, and even
more so by 8 September, one can see a clear reduction in the ozone mixing ratio at 46 hPa. Through
September the ozone destruction continues and large areas of the vortex have less than 0.5 ppm of
ozone. The maximum depletion is reached around 1 October. From 1 to 11 October one can see that
the ozone depleted region is shrinking, but there are still large areas with very low ozone.
Figure 7. Results from the BASCOE data assimilation model (run for the MACC stratospheric service) at the
level of 46 hPa on several dates from 1 July to 11 October. The upper row shows the mixing ratio of
hydrochloric acid, the middle row shows the sum of active chlorine and its dimer (ClO + 2Cl2O2), and the lower
row shows the mixing ratio of ozone. Figure copied from the WMO/GAW Antarctic Ozone Bulletin No 4/2014:
the plots were produced at WMO.
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4
4.1
Ozone depletion
Analyses of satellite observations
MACC delivers global analyses of stratospheric ozone in Near-Real Time (latency 1 to 4 days)
obtained by the assimilation of satellite observations in 4 different Data Assimilation Systems:
MACC_osuite, BASCOE, TM3DAM, SACADA (Lefever et al., 2015). This report shows results by the
main system (MACC_osuite) and also those by BASCOE and TM3DAM because they were used in the
Antarctic Ozone Bulletins issued by WMO GAW.
Let us first check the quality of these ozone analyses in the lower stratosphere. Figure 8 shows the
time evolution of the averaged ozone volume mixing ration poleward of 60°S, as delivered by the
MACC_osuite and BASCOE and observed by independent (OSIRIS; OMPS-Limb) or assimilated (MLS)
instruments. We see that the analyses do reproduce MLS extremely well. The disagreement with
OSIRIS and OMPS-Limb is partly due to sampling errors, i.e. these instruments do not have a
coverage as dense as MLS.
Figure 8: Ozone mixing ratio (ppmv) at 20 km altitude, averaged over the Antarctic latitude band (60°S-90°S)
from June to December 2014.
Hence the ozone analyses delivered by MACC_osuite and BASCOE, which are well resolved vertically,
allow the monitoring of the ozone hole at specific levels in the lower stratospere. Figure 9 shows
maps of ozone abundance at 50hPa by the MACC_osuite every day between 6 and 11 October and
between 30 October and 4 November 2014. We see that the polar vortex is shifted towards the
Atlantic sector and South America during long periods. This situation will impact the observations at
Ushuaia.
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Figure 9: MACC_osuite ozone maps between 6 and 11 October (top) and 30 October – 4 November 2014
(bottom) delivered by the MACC stratospheric ozone service (http://copernicus-stratosphere.eu/).
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Thanks to the assimilation system TM3DAM (Van der A et al, 2010) the MACC stratospheric ozone
service also delivers analyses of total ozone columns which can be compared in a consistent manner
with those on previous years. Figure 10 shows minimum ozone columns as measured by the GOME2 instrument on board MetOp in comparison with data for recent years back to 2007 (SCIAMACHY
and GOME-2). The minimum values of total ozone passed through a minimum on 1 October and
then they were on the way back up. On 16 October the minimum value was 146 DU. In August,
September and so far in the first half of October the minimum columns have been close to average
in comparison to the seven most recent years. Since then they did not recovered as quickly as the
precedent two years yielding a deficit up to 25% w.r.t. 2012 at the end of November. According to
data from NASA, the minimum daily ozone went through a minimum of 114 DU on 30 September.
Figure 10: Time series of lowest ozone column value in Dobson Units (DU) for latitudes below 30° South.
Data generated for MACC by the TM3DAM system assimilating SCIAMACHY on Envisat (until 2011) or
GOME-2 on MetOp-A (since 2012). Figure copied from the MACC service for stratospheric ozone at KNMI
(http://www.temis.nl/protocols/o3hole/).
Figure 11 shows satellite maps from OMI for 7 October for the years 2006 - 2014. From these maps
one can see that ozone depletion in 2014 is similar to that seen in 2011 and 2013 and covering a
larger area than in 2012. On the other hand, the ozone-depleted region covers a smaller area on 7
October in 2014 as compared to the same date in 2006 and 2008.
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Figure 11: Maps of total ozone on 7 October for the years 2006 – 2014. Data generated for MACC by the
TM3DAM system assimilating SCIAMACHY on Envisat (until 2011) or GOME-2 on MetOp-A (since 2012).
Figure copied from the WMO Antarctic Ozone Bulletin No 4/2014.
Figure 12: MACC_osuite and BASCOE analyses of total ozone for 7 October 2014. Data produced for the
Copernicus stratospheric ozone service : http://www.copernicus-stratosphere.eu/.
Figure 12 shows that on 7 October 2014, the two other MACC assimilation systems for stratospheric
ozone (MACC_osuite and BASCOE) deliver total ozone columns which agree very well with the
TM3DAM results used by the Antarctic Ozone Bulletin.
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4.2
Ozone hole area and mass deficit
The area of the region where total ozone is less than 220 DU (“ozone hole area”) as deduced from
the GOME-2 instrument on Metop (and SCIAMACHY on Envisat in the past) is shown in Figure 13
(left). During the first half of August, the area increased more slowly than at the same time in many
of the recent years. However, during the last half of August and the first couple of weeks of
September it increased at about the same rate as in recent years. The ozone hole area reached a
maximum so far this year on 11 September with 24.06 million square kilometres. That is close to the
maximum reached in 2013 (23.77 million km2).
The amount of ozone, measured in megatonnes, that has to be added to the ozone hole in order for
total ozone to come up to 220 DU is called the ozone mass deficit. The ozone mass deficit as
calculated by KNMI based on GOME-2 data is shown in Figure 13 (right). The ozone mass deficit has
developed in 2014 similarly to recent years till mid October.
The ozone mass deficit reached a maximum of 30.1 megatonnes on the 1st of October. That is more
than the 24.6 megatonnes reached in 2013 and the 21.6 megatonnes reached in 2012, but less than
the 36.8 megatonnes reached in 2011. Averaging over the period from 7 September to 13 October,
the ozone hole area was 19.2 million square kilometres in 2014 vs 19.3 million square kilometres in
2013 and 17.0 million square kilometres in 2012. The ozone mass deficit averaged over the same
time period reached 15.5 megatonnes in 2014 vs 15.9 megatonnes in 2013 and 12.8 megatonnes in
2012. Therefore, the 2014 ozone hole is very similar to the one of last year and significantly larger
than the one of 2012. However, from mid October observations show a very different evolution
from the precedent two years with a larger area below 220 DU that disappears only at the beginning
of December, contrary to the last two precedent years when the extinction took place early in
November.
Figure 13: Left: ozone hole area for the years from 2007 to 2014 (black dots). Right: ozone mass deficit for the
years from 2006 to 2014 (black dots Data generated for MACC by the TM3DAM system assimilating
SCIAMACHY on Envisat (until 2011) or GOME-2 on MetOp-A (since 2012). Figure copied from the MACC
service for stratospheric ozone at KNMI (http://www.temis.nl/protocols/o3hole/).
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4.3
Ground-based and balloon observations
The map in Figure 15 shows the location of the stations that provide data during the ozone hole
season using ground-based or ballon observations. Measurements with ground based instruments
and with balloon sondes show clear signs of ozone depletion at most sites.
Figure 15: map of ground-based and balloon stations used in the Antarctic Ozone Bulletin No 4/2014
In 2014 the polar vortex has been shifted towards the Atlantic sector and South America during long
periods. This has led to low ozone over stations on this side of the continent and even reaching as
far north as Ushuaia. Stations facing the Pacific sector have been outside of the vortex for long
periods and have experienced large total ozone values. We show here results from the South Pole
and Ushuaia stations. The South Pole was chosen for its central location, and Ushuaia (which is
typically at the edge of the polar vortex) was selected, because the MACC stratospheric ozone
service helped the station operators to plan and interpret their ozone soundings during the 2014
ozone hole season.
South Pole station
The vertical distribution of ozone at the GAW/NDACC South Pole station (Amundsen-Scott base) has
been measured by NOAA/ESRL with electrochemical concentration cell (ECC) ozonesondes since
1986. Figure 16 shows the soundings between 8 August and 16 October. From 1 September the
profiles begin showing first signs of ozone being destroyed. On 11 September one can clearly see
that ozone depletion has started with a large “ozone” bite-out centered around 20 km. From 11 to
23 September one can see a gradual decline in the amount of ozone. The 14-21 km partial ozone
column measured on 8 October (13 DU) is among the lowest measured so far at any station this
year. Ozone is still well below 220 DU on 12 and 16 October. The 12-20 km column on 16 October is
the lowest measured at the South Pole this year and one has to go back to 2011 in order to find a
lower value for this partial column.
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The total ozone values indicated on Figure 16 were measured with a Brewer spectrophotometer.
Temperatures remained cold in the stratosphere and on 11 September the temperature was -89.7°C
at 18.9 km. On 26 September the lowest temperature was -84.3°C at 17.0 km. On the 26th of August
one can see that ozone depletion does not affect the South Pole to any large extent yet. On 19
September ozone depletion is clearly visible, but there are regions to the north that are slightly more
depleted than the South Pole. Only four days later one can see that ozone depletion has progressed
further and on 8 October the South Pole is inside the most depleted region with less than 15 DU of
partial column.
Figure 16: Ozonesonde profiles measured at the South Pole from 8 August until 16 October 2014. Plots taken
from the WMO Antarctic Ozone Bulletin No 4/2014.
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Ushuaia Station
The global GAW station Ushuaia (54.848°S, 68.310°W) is operated by the Servicio Meteorológico
Nacional of Argentina. This station is mainly influenced by middle latitude air masses, but on certain
occasions the south polar vortex sweeps over the southern tip of the South American continent. On
such occasions Ushuaia can be on the edge of or even inside the ozone hole.
Figure 17: Total ozone over Ushuaia in 2014. The orange circles show total ozone deduced from ozone balloon
soundings, the red curve with dark red dots shows the Dobson observations (until 12 October) and the blue
diamonds show OMI overpass data (until 6 October). The thick grey line shows the median total ozone value
for each day based on MSR and TM3 data for the 1992-2012. The light grey shaded area shows the range of
total ozone values over the same time period.
Figure 17 shows total ozone measurements (Dobson spectrophotometer) together with OMI
overpass and ozonesondes data. One can see the excellent agreement between Dobson and the
ozonesondes measurements. Ozone profiles are measured with electrochemical ozonesondes
approximately twice per month from June until the end of the ozone hole season. The ozonesonde
data for 2014 are shown in Figure 18. One can see that on 16 September, when the edge of the
ozone hole passed over the station, the 12-20 km partial ozone column is substantially lower than
for the other soundings.
Figure 18: Ozonesonde profiles measured at Ushuaia from 4 June to 10 October 2014. Plots taken from the
WMO Antarctic Ozone Bulletin 4/2014.
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5
References
Errera, Q. and Ménard, R.:
Technical Note: Spectral representation of spatial correlations in variational assimilation with grid
point models and application to the Belgian Assimilation System for Chemical Observations
(BASCOE),
Atmos. Chem. Phys., 12, 10015–10031, doi:10.5194/acp-12-10015-2012, 2012.
Inness, A., Baier, F., Benedetti, A., Bouarar, I., Chabrillat, S., Clark, H., Clerbaux, C., Coheur, P.,
Engelen, R. J., Errera, Q., Flemming, J., George, M., Granier, C., Hadji-Lazaro, J., Huijnen, V.,
Hurtmans, D., Jones, L., Kaiser, J. W., Kapsomenakis, J., Lefever, K., Leitão, J., Razinger, M.,
Richter, A., Schultz, M. G., Simmons, A. J., Suttie, M., Stein, O., Thépaut, J.-N., Thouret, V.,
Vrekoussis, M., Zerefos, C., and the MACC team:
The MACC reanalysis: an 8 yr data set of atmospheric composition.
Atmos. Chem. Phys., 13, 4073-4109, doi:10.5194/acp-13-4073-2013, 2013.
Lefever, K., van der A, R., Baier, F., Christophe, Y., Errera, Q., Eskes, H., Flemming, J., Inness, A.,
Jones, L., Lambert, J.-C., Langerock, B., Schultz, M. G., Stein, O., Wagner, A., and Chabrillat, S.:
Copernicus stratospheric ozone service, 2009–2012: validation, system intercomparison and roles
of input data sets, Atmos. Chem. Phys., 15, 2269-2293, doi:10.5194/acp-15-2269-2015, 2015.
van der A, R. J., Allaart, M. A. F., and Eskes, H. J.:
Multi sensor reanalysis of total ozone,
Atmos. Chem. Phys., 10, 11277-11294, doi:10.5194/acp-10-11277-2010, 2010.
WMO Antarctic Ozone Bulletins: 2014
http://www.wmo.int/pages/prog/arep/WMOAntarcticOzoneBulletins2014.html
Copernicus stratospheric ozone service
http://www.copernicus-stratosphere.eu/
TEMIS service for stratosperic ozone
http://www.temis.nl/protocols/o3hole/
Ozone Hole Watch service by NASA Goddard Space Flight Center
http://ozonewatch.gsfc.nasa.gov/
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