- Angell, J.K. OAR/Air Resources Laboratory
- Flynn, L.E. NESDIS/Office of Research and Applications
- Gelman, M.E. NWS/Climate Prediction Center
- Hofmann, D. OAR/Climate Monitoring and Diagnostic Lab.
- Long, C.S. NWS/Climate Prediction Center
- Miller, A.J. NWS/Climate Prediction Center
- Nagatani, R.M. NWS/Climate Prediction Center
- Oltmans, S. OAR/Climate Monitoring and Diagnostic Lab.
- Zhou, S. RS Information Systems, Inc.
Concerns of global ozone depletion (e.g. WMO, 1999) have led to major international
programs to monitor and explain the observed ozone variations in the stratosphere. In
response to these, as well as other long-term climate concerns, NOAA has established
routine monitoring programs utilizing both ground-based and satellite measurement
techniques (OFCM, 1988).
Selected indicators of stratospheric climate are presented in each Summary from
information contributed by NOAA personnel. A Summary for the Northern Hemisphere is issued
each April, and for the Southern Hemisphere, each December. These Summaries are available
on the World- Wide-Web, at the site
with location: products/stratosphere/winter_bulletins.
Further information may be obtained from Melvyn E. Gelman
W/NP52, RM 806, WWB
NOAA Climate Prediction Center
5200 Auth Road
Camp Springs, MD 20746-4304
Telephone: (301) 763-8071, ext. 7558
Fax: (301) 763-8125
Extensive ozone depletion was again observed over Antarctica during the Southern Hemisphere
winter/spring of 2003, with widespread total ozone anomalies of 30 percent or more below the
1979-1986 base period. The area covered by extremely low total ozone values of less than 220
Dobson Units, defined as the Antarctic "ozone hole" area, was as large as in any previous year. The
ozone hole reached maximum size of greater than 27 million square kilometers, with an average size
in September of 25.8 million square km, larger than for any previous year.. Vertical profiles of
ozone amounts, measured by balloons over the South Pole, showed strongest destruction of ozone
in the 15-21 km region. At the South Pole, the minimum total ozone value of 106 Dobson Units, was
observed on 26 September 2003, when the center of the ozone hole was nearby. Minimum values
were not as low as seen during other recent years. Lower stratosphere temperatures below -78 C
(sufficiently low for polar stratospheric cloud formation) in the winter of 2003 occurred again over
the Antarctic region, thus promoting chemical ozone loss. However, meteorological conditions of
warming over Antarctica in early October limited further severe ozone destruction and also limited
the extent and duration of the ozone hole in 2003.
I. DATA RESOURCES
The data used for this report are listed below. This combination of complementary data,
from different platforms and sensors, provides a strong capability to monitor global ozone
Method of Observation
||Balloon - Radiosonde
We have used total column ozone data from the NASA Nimbus-7 SBUV instrument from 1979
through February 1985; NOAA-9 SBUV/2 from March 1985 to December 1988; NOAA-11 SBUV/2
from January 1989 to December 1993; NOAA-9 SBUV/2 from January 1994 to December 1995;
NOAA-14 SBUV/2 from January 1996 to June 1998; NOAA-11 SBUV/2 from July 1998 to
September 2000; and NOAA-16 SBUV/2 from October 2000. Solar Backscatter Ultra-Violet
(SBUV) instruments can produce data only for daylight-viewing conditions, so SBUV/2 data are not
available at polar latitudes during winter darkness. Precession of the NOAA-11 satellite caused
SBUV/2 viewing high latitudes only in darkness and increasing data loss at sub-polar latitudes,
especially in 1992 and 1993.
Figure 1 displays monthly average anomaly values (percent) of zonal mean total ozone, as a
function of latitude (80N to 80 S) and time (January 1979 to November 2003. The anomalies are
derived relative to each month's 1979-2003 average. Certain aspects of long-term global ozone
changes may be readily seen. In the polar regions, ozone values were substantially lower in the
1990s than in the 1980s. Largest anomalies are shown for the polar regions in each hemisphere in
winter-spring months, with positive anomalies of more than 10 percent in the earlier years changing
to negative anomalies of greater than 10 percent for most recent years. In the Antarctic region winter
and spring of 2003, average total ozone again reached 10 to 30 percent lower than the long-term
Maps of monthly average Southern Hemisphere SBUV/2 total ozone for September and October
2003 are shown in Figure 2a, and Figure 3a.
Lowest "ozone hole" values (defined as total ozone values less than 220 DU) appear over Antarctica slightly displaced from the South Pole, and highest
total ozone is shown in the Pacific Ocean between Antarctica and Australia.
Figure 2b and Figure 3b show the difference in percent between the monthly mean total ozone for September and October
2003 and eight (1979-86) monthly means for those months (Nagatani et al., 1988). Extreme negative
anomalies in total ozone of greater than 45 percent are shown over most of Antarctica and adjacent
ocean areas, reaching to southern Argentina.
Figure 4a compares, for each year since 1979, the ozone hole area average for all days in October
through November. The growth in the ozone hole area from the 1980s through the 1990s is quite
apparent. From a very small area in 1982, October/November average values increased dramatically
to a maximum in 1998 of 16.4 million square kilometers. The October/November 2003 average
ozone hole area was 10.7 million square kilometers, somewhat smaller than most recent years since
1990. Figure 4b, c, and d show the individual monthly average ozone hole size for, respectively,
September, October, and November, for years since 1980. There are strong similarities in the
progression of ozone hole size in the years 2003 and 2000. The September 2003 ozone hole size was
the largest average monthly size ever (25.8 million square km). The size decreased in October, and
in November it was substantially diminished.
The center of the ozone hole and associated lowest ozone, and polar vortex are often located close
to the South Pole. Figure 5 shows a time series during 2003 of total ozone, measured over the South
Pole using balloon-borne ozone instruments, compared with other selected years. Low ozone hole
values appeared in August 2003, with lowest values evident in mid-September to October, when the
center of the ozone hole was closest to the South Pole. Total ozone values rose in early November,
when the ozone hole decreased and was displaced from the South Pole.
On 26 September (Figure 6) a very low total column ozone amount of 106 DU was observed at the
South Pole, the minimum value for the year 2003. This profile shows strong destruction of ozone
between 15 and 21 km associated with classic ozone hole conditions. The time series in
Figure 7 of ozone profiles at the South Pole during 2003 shows the time sequence of dramatic decreases in
ozone between 15 and 21 km especially evident in September. Extremely low values of ozone
associated with ozone hole conditions continued in October, but moderated thereafter.
One of the longest records of ozone measurements in Antarctica is the total column ozone amount
obtained with the Dobson spectrophotometer at South Pole Station. Consistent observations can be
obtained beginning on October 15 of each year when sufficient sunlight is available for these optical
measurements that use the sun as a light source. This record of average October 15-31 column
amounts shown in Figure 8 indicates declines that accelerated in the 1980s and reached consistently
low values from 1993-1999. Since 2000 there has been greater variability in this average with the
suggestion of a tendency toward greater amounts than seen during the 7-year minimum period.
Ozone amounts in the lower stratosphere are closely coupled to temperatures through dynamics and
photochemistry. Extremely low stratospheric temperatures (lower than -78 C) over the Antarctic
region contribute to depletion of ozone, in that low temperatures lead to the presence of polar
stratospheric clouds (PSCs). PSCs enhance the production and lifetime of reactive chlorine, leading
to ozone depletion (WMO, 1999). Daily minimum temperatures at 50 hPa (approximately 19 km)
over the polar region, averaged from 65S to 90S are shown in Figure 9.
For most of the Southern Hemisphere winter of 2003, minimum temperatures in the south polar region were below -78 C,
below long term average minimum values, and indeed near record low temperatures. The rise in
temperatures higher than -78 C in October 2003 limited the further formation of polar stratospheric
clouds and thus also limited further extreme ozone destruction. Temperatures in the winter and
spring of 2003 were much lower than in 2002, and coincided with a much stronger ozone hole in
2003 than in 2002.
Figure 10 shows monthly average temperature anomalies at 50 hPa for three latitude regions,
25S-25N, 65S-25S, and 90S-65S. For the south polar region, winter temperatures were much lower
than the long-term average, but positive anomalies were observed in October and November. This
was similar to the sequence of events in 2000 and 2002. Negative temperature anomalies
predominated over the middle latitudes of the Southern Hemisphere, with very large negative
anomalies over tropical latitudes. Both the tropical and middle latitudes of the Southern Hemisphere
continue the tendency toward lower temperatures after 1993 relative to higher temperatures in earlier
Figure 11 presents time series of the area of the ozone hole, the size of the polar vortex, and the size
of the polar area where lower stratosphere temperatures were below -78 C (polar stratospheric cloud,
PSC area). The daily 2003 values are shown, along with the extreme and average daily values for
the most recent 10 years. During the spring of 2003, the area for all three indicators was larger than
average during August, September, and the first part of October. Indeed, the ozone hole was larger
in August and several days in September 2003 than for any other recent years. The steady decrease
in October of the ozone hole coincided with the decrease in size of the Southern Hemisphere polar
vortex and the decrease in size of the area of very low temperatures. The size of the ozone hole
correlates well with the size of the PSC area during the formation stages of the ozone hole through
the first half of September. Thereafter, the ozone hole size is strongly affected by the size of the
Figure 12 illustrates the direct relationship between the persistence of the ozone hole and the
persistence of the Antarctic polar vortex. In years when the winter polar vortex persisted later in the
season, the duration into the Spring season of the ozone hole also tended to be extended. For the
year 2003, the persistence of the ozone hole and the persistence of the Southern Hemisphere polar
vortex extended longer than most years since the ozone hole developed, but shorter than most of the
years since 1990.
III. CONCLUDING REMARKS
Very low ozone values were again observed over Antarctica in the winter/spring of 2003. Ozone
depletion of more than 40 percent was observed over Antarctica, compared to total ozone amounts
observed in the early 1980's. Vertical soundings over the South Pole during August, September and
October 2003 again showed strongest destruction of ozone at altitudes between 15 and 21 km.
Lower stratosphere temperatures in the winter of 2003 over the Antarctic region were also much
lower than average values. Associated with this, the ozone hole area in August and September was
among the largest of any previous year. The ozone hole diminished in October and November along
with warming stratospheric conditions. So although the Antarctic ozone hole in 2003 reached
unprecedented size, the duration of the extremely low ozone conditions was limited by warmer
meteorological conditions which developed in October and November.
Observations of chloroflourocarbons and of stratospheric hydrogen chloride support the view that
international actions are reducing the use and release of ozone depleting substances (WMO, 1999;
Anderson et al., 2000). However, chemicals already in the atmosphere are expected to continue to
deplete ozone for many decades to come. Further, changing atmospheric conditions that modulate
ozone can complicate the task of detecting the start of ozone layer recovery. The eruption of the
Pinatubo volcano provided an example of such a complication in the 1990s. Based on an analysis
of 10 years of South Pole ozone vertical profile measurements, Hofmann et al., (1997) estimated that
recovery in the Antarctic ozone hole may be detected as early as the coming decade. Indicators
include: 1) an end to springtime ozone depletion at 22-24 km, 2) 12-20 km mid-September column
ozone loss rate of less than 3 DU per day, and 3) a 12-20 km ozone column of more than 70 DU on
September 15. An intriguing aspect of recent observations of the Antarctic stratosphere had been
the apparent trend towards a later breakup of the vortex in most recent years. The large size of the
August-September 2003 ozone hole but its limited duration in October-November is attributed in
part to meteorological conditions. A full explanation of such meteorological anomalies is not yet
available. Continued monitoring and measurements, including total ozone and its vertical profile,
are essential to achieving the understanding needed to identify ozone recovery.
Anderson, J., J. M. Russel III, S. Solomon, and L. E. Deaver, 2000: Halogen Occultation Experiment
confirmation of stratospheric chlorine decreases in accordance with the Montreal Protocol,
J. Geophys. Res., 105, 4483-4490.
Hofmann, D.J., S.J. Oltmans, J.M. Harris, B.J. Johnson, and J.A. Lathrop, 1997: Ten
years of ozonesonde measurements at the south pole: implications for recovery of
springtime Antarctic ozone. J. Geophys. Res., 102, 8931-8943.
Miller, A.J., dt al.,A cohesive total ozone data set from
SBUV/(2) satellite system, in press, J.Geophys. Res., 2002.
Nagatani, R.N., A.J. Miller, K.W. Johnson, and M.E. Gelman, 1988: An eight year
climatology of meteorological and SBUV ozone data, NOAA Technical Report NWS 40, 125 pp.
OFCM, 1988: National Plan for Stratospheric Monitoring 1988-1997. FCM-P17-1988. Federal
Coordinator for Meteorological Services and Supporting Research, U.S. Dept. Commerce,
Planet, W. G., J. H. Lienesch, A. J. Miller, R. Nagatani, R, D. McPeters, E.
Hilsenrath, R. P. Cebula, M. T. DeLand, C. G. Wellemeyer, and K. M. Horvath, 1994:
Northern hemisphere total ozone values from 1989-1993 determined with the NOAA-11 Solar
Backscatter Ultraviolet (SBUV/2) instrument. Geophys. Res. Lett., 21,
WMO, 1999: Scientific assessment of ozone depletion: 1998. World Meteorological
Organization Global Ozone Research and Monitoring Project - Report No. 44.
VI. Web Pages of Interest