3. ARCTIC STRATOSPHERIC OZONE ANOMALY IN 1997 SPRING
Toshihiro Ogawa
Coordinator of ADEOS Atmospheric Science
Invited Scientist, JAXA EORC
Professor, University of Tokyo
The depletion of stratospheric ozone is most conspicuous in the Antarctic
spring because of the appearance of the Ozone Hole. In the Northern
Hemisphere, a decreasing tendency in lower stratospheric ozone was
strengthened in the 1990s in the polar and high-latitude regions in winter
and spring. In the winter of 1996/97, as expected by many meteorologist, the
polar vortex was weak and stratospheric temperature was not too cold in the
early phase. However, the polar vortex developed significantly in February
1997 and lasted until mid-April 1997. Due to this meteorological situation,
the NASA balloon team had to postpone the flight of stratospheric balloons at
Fairbanks, Alaska by about one month. The flight was the major event of the
ADEOS Alaska Campaign that conducted observations with stratospheric balloons,
ozonesondes, ground-based lidar, and spectroscopic instruments in correlation
with the TOMS, ILAS and IMG observations aboard ADEOS.
According to the TOMS observation, total ozone reached record lows this year
in Mid-March through Mid-April in the polar Northern Hemisphere, with the
minimum of about 220 Dobson Units occurring around 20 March. Furthermore,
during mid-March to early April, the shape of low total ozone area was very
similar to that of the Antarctic Ozone Hole. This phenomenon may be called the
"Arctic Ozone Hole," but we should continue observations for the next few
springs before we definitely declare it. ILAS and IMG observations also showed
a similar signature of stratospheric ozone in the Arctic spring this year.
These instruments also obtained data on other stratospheric trace species
related to ozone. Those data will be analyzed together with those from many
ground-based correlative observations carried out in Northern Europe, Alaska,
Canada and Siberia, to reveal the chemical and dynamic characteristics of the
Arctic ozone anomaly in the spring of 1997.
Earth Observation Research Center