John Bluck
NASA Ames Research Center, Moffett Field, CA
650/604-5026 or 650/604-9000,

Harvey Leifert (contact until May 26 and for media registration)
American Geophysical Union (AGU), Washington, DC

AGU Press Room (contact from May 30 on and for media registration)
Washington Convention Center, 900 9th St. NW
Washington, DC
202/371-5087, fax 202/371-5093,


The culprits in the major ozone loss in the Arctic stratosphere earlier this year were unusually
long-lasting polar clouds made of nitric acid crystals, according to preliminary results from an
international field experiment.

The new evidence also confirms scientists’ suspicions that an ozone-destroying chemical process not
thought to be active over the northern pole is occurring, which could foreshadow greater ozone losses
in the future. This research on the ozone-destroying role of polar stratospheric clouds (PSCs) will be
presented next week at the American Geophysical Union’s Spring Meeting in Washington, D.C. A
news briefing is scheduled for Tuesday, May 30, at 12:15 p.m. EDT in the Washington Convention
Center. Three thousand earth scientists are expected at this year’s meeting.

“Even the very small numbers of particles observed in PSCs during our experiment can efficiently
remove nitrogen from the stratosphere,” said Eric Jensen, a scientist from NASA’s Ames Research
Center, located in California’s Silicon Valley, who will be one of the briefing panelists. “We found that
the clouds lasted longer during the 1999/2000 winter than during past winters, allowing greater
ozone depletion over the Arctic.”

Click here to reach links to images of polar stratospheric clouds in high enough resolution for some publications.

Scientists involved in a recent NASA/European Commission field experiment in Sweden will discuss
their preliminary results at the briefing. Topics include the formation of PSCs by waves in the
atmosphere created by mountain ranges, and indications that “denitrification” may now be taking
place over the Arctic, a process that can delay the natural shut-off of ozone-destruction as spring

The new observations were collected by aircraft, balloons, and satellites during the joint SAGE III
Ozone Loss and Validation Experiment (SOLVE) and the European Stratospheric Experiment in Ozone
(THESEO), conducted between December 1999 and March 2000.

More information about the NASA-sponsored SOLVE campaign and the European
Commission-sponsored THESEO 2000 experiment (including a list of participating institutions) is on
the Internet at:

THESEO 2000) —

In addition to Jensen, participants in the AGU news briefing include: Edward V. Browell, NASA
Langley Research Center, Hampton, VA; Ken Carslaw, University of Leeds, United Kingdom; Michael
J. Kurylo, NASA’s Upper Atmosphere Research Program, NASA Headquarters, Washington, DC; and
Brian Toon, University of Colorado, Boulder, CO.

Video and new data animations will be distributed at the AGU news briefing. Color photographs of
polar stratospheric clouds from the recent field experiment are available on the Internet at: