Indian Journal of Radio Space Physics
Vol. 35, August, 2006, pp. 253-258
Year-to-year variation of ozone hole over Schirmacher region of East Antarctica:
A synopsis of four-year measurement
Sachin D Ghude*, S L Jain, Pavan S Kulkarni, Ashok Kumar & B C Arya
Radio & Atmospheric Sciences Division, National Physical Laboratory
Dr K S Krishnan Marg, New Delhi 110 012, India
E-mail: [email protected]
Received 5 August 2005; revised 15 October 2005; accepted 12 July 2006
th
st
During the 16 , 21 , 22nd and 23rd Indian Antarctic expedition conducted in 1997, 2002-03 and 2004 respectively,
measurement of columnar ozone have been made using MICROTOPS II Sun-photometer from the Indian station Maitri (70º
45' S, 11º 44' E). It is found that the ozone hole depth fluctuated from year-to-year. The minimum columnar ozone observed
over Maitri was 135 (±9.3) DU, 185 (±12) DU, 126 (±9.7) DU and 159.8 (±8.8) DU during spring 1997, 2002, 2003 and
2004, respectively. Ozone concentration below 220 DU (nominal ozone threshold value) during Antarctic spring (day 225–
365) over Maitri has been observed to be 45.1 %, 20.7 %, 62.7 % and 60 % in 1997, 2002, 2003 and 2004, respectively. The
chemical loss of ozone (total ozone values below 220 DU) over Maitri during 2003 (day 225–365) was found to increase by
a factor of 0.4 when compared to 1997, and by a factor of 2 when compared to 2002. The observations at Maitri also showed
an event of major stratospheric warming during 2002. The ozone hole in the year 2002 was not found to be deep and further
recovered quite early when compared to 1997, 2003 and 2004.
Keywords: Antarctica, Ozone hole, Sudden stratospheric warming, Planetary waves, Polar vortex
PACS No.: 92.70.Cp; 93.30.Ca; 94.10.Dy
1 Introduction
Stratospheric ozone is photo-chemically controlled
by chemically active species in the oxygen, hydrogen,
nitrogen, chlorine and bromine families. Most of the
ozone is created over the tropics and transported into
the polar region by the general circulation of the
stratosphere. The total ozone column is found to
decrease at mid-latitudes of northern and southern
hemisphere1. World Meteorological Organization2
reported a 4.6 % per decade decrease in the total
ozone column during 1979-1994. The formation of
ozone hole over Antarctica during Antarctic spring is
mainly because of catalytic depletion of ozone3 due to
heterogeneous chemical reaction which take place on
the surface of the polar stratospheric cloud (PSCs)4-7.
These heterogeneous reactions under very cold
stratospheric conditions over Antarctica transform
comparatively inert ClONO2 and HCl into active
forms of chlorine compound8,9. However, the
photochemical balance, the winds that transport the
ozone and meteorological conditions in the
stratosphere influence chemical destruction of ozone
and development of the Antarctic ozone hole10.
__________________
*Present Address: Indian Institute of Tropical Meteorology
Dr. Homi Bhabha Road, Pashan, Pune 411 008
It has now been established that temperatures in the
lower stratosphere are closely coupled to ozone
through dynamics and photochemistry11 and also very
much dependent on the movement of polar vortex and
planetary waves12. Planetary waves displace air north
and south, originate in the troposphere and propagate
upward, transferring their energy to the stratosphere
and warms it13. These vast pressure waves influence
ozone destruction in several ways and can have
relevant impact on the size and stability of Antarctic
vortex14. A major warming in the stratosphere is a
wintertime dynamical phenomenon, in which rapid
and substantial transport of air between the mid- and
high-latitudes takes place, making the polar vortex
unstable. The amount of exchange between vortex
and mid-latitude air influences the amount of
chemical processing of ozone and hence total column
ozone15. Ozone column density, therefore, varies with
temperature in the lower stratosphere and movement
of air in lower stratosphere16.
This paper reports the four-year measurement of
total column ozone carried out at Schirmacher region
of East Antarctica, where Maitri, an Indian Antarctica
research station is situated. The Schirmacher oasis is
an ice-free area situated in the Princess Astrid coast of
Queen Maud Land, East Antarctica and lies between
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INDIAN J RADIO & SPACE PHYS, AUGUST 2006
70° 44′ 33″–70° 46′ 30″ S latitude and 11° 22′ 04″–
11° 54′ 00″ E longitude. It is 3800 km SE of Cape
Town, South Africa. The oasis is located between the
margin of an ice sheet and shelf ice, the low-lying
hills up to 250 m high, interspersed with glacial lakes
and ponds and occupies an area of about 35 km2.
Maitri lies at the `Schirmacher Region' of east
Antarctica at 70° 45' 58" S and 11°43' 56" E.
Here, the results of columnar ozone measurements
during the ozone-hole period in the years 1997, 2002,
2003 and 2004 are presented. Although the
measurements were made using MICROTOPS II
Sunphotometer at Maitri, the number of observations
are less because of the non-availability of clear sunny
days throughout the observational period. Therefore,
total ozone data from TOMS instrument aboard Earth
Probe (EP) satellite was received from the website
http://www.science.nasa.gov/ over the nearby Russian
station (70°45′ S, 11°40′ E). These data are used to
study inter-sequential change of total ozone during
ozone hole period. Inter-sequential change is the dayto-day variation of total ozone, that is fluctuations
yi+1–yi on successive days. TOMS samples
backscatter UV at six wavelengths (of 308.6, 312.5,
317.5, 322.3, 331.2 and 360.0 nm) provides an
accurate measurement of total columnar ozone.
TOMS instrument aboard EP satellite, launched in
July 1996 continues to provide total columnar ozone
and covers the entire globe. In the present paper
results obtained are discussed in detail.
2 Experimental setup
The observations were made using Solar Light total
ozone portable spectrophotometer (MICROTOPS II)
instrument. The MICROTOPS II is a five-channel
hand held microprocessor-controlled sun photometer.
The experimental error of the measurement of total
columnar ozone using the instrument is approximately
2 %. Out of the five channels at 300, 305, 312, 940
and 1020 nm, the first three filter channels were used
to derive atmospheric total ozone column and the rest
two for water vapour. The measurement technique
and details of the instrument are discussed
elsewhere17.
3 Results and discussion
Variation of columnar ozone over Maitri during the
ozone hole period of the year 1997, 2002, 2003 and
2004 is shown in Fig. 1. The gaps in the figure are
Fig. 1⎯Comparison of column ozone over Maitri during the ozone hole periods of 1997, 2002, 2003 and 2004
GHUDE et al.: OZONE HOLE OVER SCHIRMACHER REGION, EAST ANTARCTICA
due to non-availability of clear sky days; hence
Sunphotometer could not be used to take observations
on such days. Total ozone up to 320 DU has been
observed over Maitri during the months of January
and February during all the observational years (not
shown in Fig. 1). The minimum total ozone values of
about 135 (±9.3) DU on 25 Sep. 1997, 185 (±12) DU
on 20 Sep. 2002, 126 (±9.7) DU on 3 Oct. 2003 and
159.8 (±8.8) DU on 5 Oct. 2004 have been recorded
over Maitri during the ozone hole periods. These
observations showed that the depth of ozone hole
varied considerably from year-to-year, where the
deepest ozone hole was observed in 2003 compared to
1997, 2002 and 2004. Similarly, Fig. 2 shows the
condition of ozone hole over the nearby Russian
station, as observed by TOMS instrument aboard EP
satellite. Comparison of MICROTOPS II and TOMS
measurement is depicted in Figs 1 and 2. The
minimum total ozone values of about 122 DU on 11
Oct. 1997, 165 DU on 19 Sep. 2002, 114 DU on 24
Sep. 2003 and 137 DU on 6 Oct. 2004 have been
observed by TOMS instrument during the ozone hole
periods. Like Maitri, similar variation of total ozone
has also been observed over Russian station. Both the
255
measurements showed the prevalence of annual ozone
hole during all the observational years. However,
year-to-year variation in the depth and duration of the
ozone hole is seen over Schirmacher region of east
Antarctica. Occasionally, large fluctuation in total
ozone values has also been observed, either during the
ozone hole period or during recovery period of 1997,
2002 and 2003. However, ozone hole during 2004 do
not show such large fluctuations over the Schirmacher
region.
The day-to-day fluctuations of columnar ozone
during the different ozone hole periods are clearly
seen in Fig. 3, which displays the inter-sequential
change of the daily ozone values during 1997, 2002,
2003 and 2004. The inter-sequential change is
calculated by subtracting total ozone values at
successive days (yi+1–yi). As seen from Fig. 3, the
large fluctuations in day-to-day ozone were observed
during 2002. Also, ozone during 1997 showed similar
fluctuations during the ozone hole period. However
magnitude of fluctuation was less during deep ozone
hole period (days 275-315). Figure 3 further
illustrates large day-to-day fluctuations of total ozone
over Schirmacher region during 1997, 2002 and 2003
Fig. 2⎯Total columnar ozone observed by TOMS instrument abroad Earth Probe satellite during ozone hole periods over Russian station
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INDIAN J RADIO & SPACE PHYS, AUGUST 2006
Fig. 3⎯Day-to-day change of daily total ozone during ozone hole periods of 1997, 2002, 2003 and 2004
compared to 2004. The main conclusion drawn from
Fig. 3 is that the factors that influence the chemical
ozone destruction were quite variable year-to-year.
This indicates that the stability of ozone hole may
largely be controlled by the dynamical behaviour of
the factors that influence the chemical ozone
destruction.
As seen from Fig. 1, ozone hole during 2002
recovered earlier than that observed in 1997, 2003 and
2004. Exceptionally high columnar ozone has been
observed during the ozone hole periods of 1997 and
2002. However, compared to 2002, ozone hole during
1997 was quite deep. Columnar ozone values up to
372 DU on 7-8 Sep. 2002 and 300 DU on 23 Sep.
1997 have been observed. During 2002, observations
at Maitri showed recovery around 24-25 Sep. and
columnar ozone temporarily shot up to 420 DU in late
October during this period. This abrupt anomalously
high columnar ozone observed in 1997 and 2002 may
be attributed to enhanced advection of ozone rich air
into the polar vortex during the ozone hole periods,
which causes the unstable polar vortex condition over
Schirmacher region.
The unstable polar vortex condition observed over
Schirmacher region in 1997 and 2002 may be
attributed to planetary wave phenomenon18. The
Schirmacher region is situated in the fringe region of
the vortex. The planetary wave phenomenon forces
the ozone rich air masses from mid-latitude to polarlatitude region and the rapid displacement of the polar
vortex from a roughly symmetric circulation about the
pole to a circulation that is offset from the pole. If the
strength of these waves is high enough, the ozone rich
air mass forces itself into the polar vortex and a
sudden increase in the total ozone may take place.
Varotsos19 has performed a Fourier analysis of the 10hpa height and the temperature-time series at the high
latitude of the southern hemisphere. He found that
extremely large amplitude of planetary waves were
present, which broke up Antarctic ozone hole into two
holes20 on 24-25 Sep. 2002. After the break-up, the
polar vortex reformed and subsequently disappeared
very early. This indicates that during the reformation
of polar vortex, planetary wave activity induced
stratospheric warming, leading to weakening of the
potential vorticity and enhanced ozone content in the
fringe region of the vortex, due to horizontal mixing
of air mass from lower latitude, and therefore, filling
vortex with ozone rich air mass.
To find out the distribution of total ozone values
over Schirmacher region during ozone hole period,
frequency distribution analysis over AugustDecember period has been done against the
concentration interval of 0-135 DU, 0-150 DU, 0-220
DU and 220 DU-above, as depicted in Table 1. Total
ozone values are available for 135 days in 1997, 140
GHUDE et al.: OZONE HOLE OVER SCHIRMACHER REGION, EAST ANTARCTICA
257
Table 1⎯Frequency distribution of ozone values during ozone hole period (August to December) observed over the Maitri by TOMS
Year
Days of
observation
Values less than
135 DU
Values less than
150 DU
Values between
150-220 DU
Above 220 DU
Days of ozone
hole, %
1997
2002
2003
2004
135
140
138
125
1 (0.74%)
0%
4 (2.8%)
0%
11 (8.1%)
0%
22 (15%)
4 (3.2%)
50 (37%)
29 (20.7%)
65 (47.8%)
71 (56%)
73
111
66
50
45.1%
20.7%
62.7%
60%
days in 2002, 138 days in 2003 and 125 days in 2004
during the ozone hole periods. Out of these days of
observation, ozone concentration less than 150 DU
has been observed over the period of 8.1 % in 1997, 0
% in 2002, 15 % in 2003 and 3.2 % in 2004. It
appears that the ozone hole in 2003 was much deeper
as compared to 1997, 2002 and 2004. Similarly,
ozone concentration below 220 DU (nominal ozone
threshold value) during Antarctic spring (day 225–
365) has been observed 45.1 % in 1997, 20.7 % in
2002, 62.7 % in 2003 and 60 % in 2004. It appears
from Table 1 that the chemical loss of ozone (total
ozone concentration below 220 DU) over
Schirmacher region during 2003 (day 225-365) was
found to increase by a factor of 0.4 when compared to
1997, and by a factor of 2 when compared to 2002.
Out of 140 days, on not more than 20.7 % days ozone
concentration below 220 DU and 0% days below 150
DU were observed during 2002, which indicates that
the chemical ozone destruction inside the vortex
during 2002 was significantly very less.
Figure 4 shows the monthly averaged temperature
anomalies at 50 hPa for the latitudinal region 90 ºS–
65 ºS. Anomalies are departures from the 1979-99
base period mean. The figure is taken from the
NOAA/
National
Weather
Center
website
(http://www.cpc.ncep.noaa.gov/products/analysis_mo
nitoring/bulletin/figs3.html).
YEAR
Fig. 4⎯Monthly averaged temperature anomalies at 50 hPa for
the latitudinal region 65 OS – 90 OS
Negative temperature anomaly up to approximately
–2 ºC was observed during spring and winter of 2004.
While as compared to 2004, slightly higher negative
temperature up to anomaly – 5 ºC was observed
before and during ozone hole period, but showed
warming in November and December 2003. However,
unusual strong positive temperature anomaly up to 10
ºC magnitude was observed during ozone hole period
in 2002. In 1997, positive temperature anomaly was
observed quite early before ozone hole period,
followed by cooling in July-August and again
warming in September-October. This temperature
anomaly is found to coincide with observed variation
in total ozone in 1997, 2002, 2003 and 2004. It
appears that the magnitude of planetary waves and the
heat flux transport toward the South Pole and upward
transport of the wave energy was unprecedented in
the year 2002 in southern hemisphere (SH), and weak
but positive in the year 1997. However, in the years
2003 and 2004, magnitude of heat flux transported by
planetary waves was unusually weak while the ozone
hole was forming during August and early September.
4 Conclusion
Year-to-year variations in the depth and duration of
the ozone hole over Schirmacher region of east
Antarctica are observed. Comparison with monthly
averaged temperature anomalies at 50 hPa for the
latitudinal region 65 ºS–90 ºS reveals the direct
relationship between the stratospheric temperature
anomaly and variation in total ozone over the
Antarctica. The day-to-day change of total ozone over
Schirmacher region indicates that the chemical ozone
destruction inside the polar vortex, stability and
duration of ozone hole is largely controlled by the
dynamical behaviour of the factors that influence the
chemical ozone destruction. The abrupt anomalously
high total ozone observed in 1997 and 2002 showed
enhanced advection of ozone rich air into the polar
vortex during ozone hole period, which causes the
unstable polar vortex condition over Schirmacher
region. The early recovery of ozone hole in 2002 can
be attributed to major stratospheric warming due to
INDIAN J RADIO & SPACE PHYS, AUGUST 2006
258
prevalence of stronger planetary waves. However, the
appearance of deeper ozone hole for longer period
over Schirmacher region in 2003 and 2004 confirmed
that weaker ozone hole observed in the year 2002
does not denote a recovery of the ozone layer. Ozone
hole data for the years 1997, 2002-03-04 does not
give any indication of the long-term trend.
Acknowledgement
The authors are thankful to the Director, NPL and
Head, RASD, for their encouragement during the
progress of the work. Thanks are also due to CSIR,
New Delhi and NCAOR (Department of Ocean
Development), Goa for financial and logistic
assistance. TOMS data have been taken from National
Space Science Data Center website (http://
www.science.nasa.gov). Monthly averaged temperature anomalies at 50 hPa for the latitude band of 65
ºS–90 ºS have been taken from NOAA/National
Weather Center website. Some data have also been
taken from SCAR (Scientific Committee on Antarctic
Research) website under REDERA project.
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