Paula Cleggett-Haleim
Headquarters, Washington, D.C.                     April 14, 1993
(Phone:  202/358-0883)

James H. Wilson
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone:  818/354-5011)

RELEASE:  93-068

OZONE DESTROYING CHLORINE EXISTED LONGER IN 1992-93 WINTER

     Ozone-destroying forms of chlorine existed for much longer in
the Arctic stratosphere this winter than last, say scientists.

     Northern Hemisphere ozone abundance also was observed to be
some 10 percent below that measured during the same period last
year, with some regions 20 percent lower.

     Using NASA's Upper Atmosphere Research Satellite (UARS), Dr.
Joe Waters and his colleagues at the Jet Propulsion Laboratory
(JPL), Pasadena, Calif., and Edinburgh University, Scotland, have
collected daily maps of ozone and other gases and of temperature
in different layers of the stratosphere.  One of their most
critical measurements is of chlorine monoxide, a form of chlorine
that destroys ozone.  They reported the results in the
international scientific journal Nature.

     "Ozone concentrations in the Arctic in a layer about 12 miles
(20 kilometers) high, where most chlorine monoxide was located,
decreased by 0.7 percent per day from mid-February through early
March 1993," Waters said.  Ozone levels normally increase in this
area at this time of the year, he added.

     Chlorine already in the stratosphere, from
chlorofluorocarbons, is converted to ozone-destroying forms by
chemistry occurring on clouds which form at low temperature.

     Last year, the scientists measured large abundances of
chlorine monoxide in the Arctic, but the concentrations decreased
after the stratosphere warmed in late January.  This winter, the
stratosphere remained cold through February, and chlorine monoxide
remained abundant through early March.

     About as much chlorine monoxide was seen in the northern
polar regions in February 1993 as was measured at the South Pole
before the 1992 Antarctic ozone hole formed.

     "We do not see a well-defined area of ozone loss that could
be described as an Arctic ozone hole," Waters said, "but the
smaller abundances of ozone seen throughout the Northern
Hemisphere this winter raise the question of whether the chlorine
destruction of ozone has been spread over a wider area."  Record
low values of ozone also have been reported recently by the World
Meteorological Organization and Environment Canada.

     The microwave limb sounder aboard UARS was developed and is
operated by JPL, led by Waters and sponsored by NASA's Office of
Mission to Planet Earth.  Additional members are from Edinburgh
University, Heriot-Watt University and the Rutherford-Appleton
Laboratory in the United Kingdom.

     UARS, launched Sept. 12, 1991, aboard Space Shuttle
Discovery, is managed by NASA's Goddard Space Flight Center,
Greenbelt, Md.

- end -

EDITORS NOTE:  A video and three color-map images are available by
calling NASA Headquarters Broadcast and Imaging Branch on 202/358-
1900.

  The photo numbers are:

                  Color                          B & W
                  93-HC-134                      93-H-146
                  93-HC-135                      93-H-147
                  93-HC-136                      93-H-148