Brian Dunbar
Headquarters, Washington, D.C.                                               
October 9, 1991
(Phone:  202/453-1547)

Dolores Beasley
Goddard Space Flight Center, Greenbelt, Md.
(Phone:  301/286-2806)


RELEASE:  91-168

1991 Antarctic OZONE levels REACH RECORD LOW


     Ozone levels in the Antarctic have reached the lowest values 
ever observed, according to preliminary data obtained by 
officials at NASA's Goddard Space Flight Center, Greenbelt, Md.

     The preliminary data from the Total Ozone Mapping 
Spectrometer (TOMS) on NASA's Nimbus-7 satellite indicate that 
ozone values of less than 120 Dobson units have been measured.  
Values as low as 110 (plus or minus 6) were observed on Oct. 6, 
however, validation of these numbers is dependent on final 
calibration.

     "The minimum ozone on Oct. 6, 1991, is the lowest we have 
ever seen with the TOMS instrument in its 13-year record of 
data," said Goddard scientist Arlin Krueger.  "Although the data 
are preliminary, we expect that the final results will confirm 
this conclusion."

     This is the fourth severe ozone hole since 1986 and the 
third consecutive year that severe ozone depletion has developed 
over the Antarctic.  The implications of a single-day minimum are 
uncertain.  The severity of each year's ozone hole also is 
measured by the persistence of the depletion through the southern 
spring and its geographical extent across Antarctica.

     Though research has linked man-made chlorine compounds and 
other chemicals to ozone depletion, the extreme magnitude 1991 
minimum cannot necessarily be attributed solely to chemical 
processes, said Dr. Jack A. Kaye, head of NASA Headquarters' 
Atmospheric Chemistry Modelling and Analysis Program.  
Meteorological processes can cause temporary small fluctuations 
inside a chemically produced ozone hole.

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     Ozone, a molecule made up of three atoms of oxygen, 
comprises a thin layer of the upper atmosphere that absorbs 
harmful ultraviolet radiation from the Sun.  The ozone hole is a 
large area of intense ozone depletion over the Antarctic 
continent that occurs typically during late-August through 
early-October and breaks up in mid-November.

     This is the 13th year that the ozone hole has been monitored 
using the TOMS on the Nimbus-7 spacecraft.  Both are managed by 
the Goddard Space Flight Center.  On Aug. 15, a refurbished 
engineering model of TOMS was launched aboard a Soviet Meteor-3 
spacecraft.  This new instrument began gathering data soon after 
launch and also has observed this year's ozone hole. 

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