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2.5. SATELLITE GROUP 89
2.5.18 GOME observations of stratospheric trace gas distributions during
the split vortex event in the Antarctic winter 2002
Participating scientists: Walburga Wilms-Grabe, Steffen Beirle, Sven Kühl, Ulrich Platt, and
Thomas Wagner
Abstract In the austral winter/spring 2002, an unusual major stratospheric warming led to an early
split of the south polar vortex, combined with a partly filling up of the Antarctic ozone hole. This
study is dealing with distributions of ozone related trace gases (O3, NO2 and OClO) measured by
GOME during the split vortex event.
GOME O 3, 2002/09/27
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ESA / DLR / IUP Bremen eichmann@iup.physik.uni-bremen.de <
Figure 2.52: O3, NO2 and OClO-distributions above the south pole at 27 Sep. 2002, measured by
GOME, retrievals of IUP Bremen (O3) and IUP Heidelberg (NO2, OClO).
Background Unusual high activity of planetary
waves in the southern hemisphere led to the
early weakening and splitting of the south polar
vortex in winter/spring 2002 and strongly affected
also chemical conditions in the Antarctic atmosphere.
This could be clearly seen from the premature
break up of the ozone hole in the last third
of September [Richter et al., 2005]. The stratospheric
ozone chemistry is related to the nitrogen
and to the halogene chemistry. Therefore, it
is of interest to investigate the evolution of O3,
NO2 and OClO during this abnormal situation,
whereas OClO serves as indicator for the degree
of stratospheric chlorine activation.
Funding See satellite group overview.
Methods and results The stratospheric ozone
chemistry is closely connected to shape and
strength of the vortex. Therefore, the polar
ozone distribution reproduces precisely the actual
state of the vortex. The break up starts at Sep.
21st/22nd. Simultaneously with the weakening of
the ozone hole NO2 is increasing inside the vortex.
At 26/27 Sep. NO2 shows unusual high
SCDs above the pole, although the ozone concentration
is still relatively low in the same area
(see figure). As well dynamical as chemical processes
can be responsible for the increased NO2
concentrations. One important aspect is the vertical
misalignment and realignment of the vortex
during the weakening period. Also thermal decay
and rapid photolysis of NO2 reservoirs of warm
mid-latitude air transported to polar regions may
contribute to the NO2-enrichment. OClO evinces
high chlorine activation inside the vortex at 20
Sep. and is rapidly decreasing after 22 Sep. At 27
Sep. GOME does not find OClO any more (figure).
Even after the re-establishing of one vortex
fragment by mid October over the pole no OClO
was observed. The rapidity of the OClO reduction
in the austral spring 2002 is anomalous. In
contrary to the north pole where high yearly variability
of OClO is typical, the chlorine activation
above the south pole varies only slightly from year
to year. In the year 2002 however the decrease of
OClO starts about 10 days earlier as usual and
continues for approximately 7 days only.
Outlook/Future work Including measurements
of polar stratospheric clouds (e.g. from
ENVISAT-MIPAS) and limb observations of different
trace gases by SCIAMACHY during the
split vortex event can provide new insights in the
chemical and dynamical interactions also with vertically
resolved information.
Main publication Wilms-Grabe et al. [2004],
Richter et al. [2005]