A single multi-panel image, 512x512 pixels, 8-bit Macintosh LUT color
in HDF format, with a customized palette for multi-panel display.  The
top row of panels depicts.the ozone distribution over the Earth as
derived from the ultraviolet sensors on NASA's NIMBUS satellite.  The
middle row is the corresponding ozone estimate from NOAA's infrared
sensors on the NOAA's TOVS instrument.  False colors are used to
indicate the effective total thickness of the ozone layer, with a
major color change every 0.5 mm of ozone.  (1 mm of ozone is equal to
100 "Dobson Units", abbreviated as "DU/100".)

The two satellites agree upon the large scale ozone distribution, but
there are significant differences between the two estimates.  The
difference field is presented in the small panel in the center of the
bottom row, where red is used to indicate regions where the infrared
TOVS measurements are significantly greater than the corresponding
ultraviolet TOMS measurements, and blue for under-estimates.  On this
day, the infrared estimates are too high over the Sahara desert, and
too low over the Antarctic during the "ozone hole" episode.

To validate the two satellite datasets, corresponding surface-based
ozone measurement from the small network of Dobson instruments around
the world are presented in the map in the lower left panel.  A
quantitative assessment is presented as a scatter plot in the lower
right panel -- TOMS vs.  DOBSON (green dots) TOVS vs DOBSON (yellow
dots), and root-mean-square statistics among the three pairs of
measurements (multi-color bars).  This image is one of 120 days
compared during the great "ozone hole" episode of 1987.

GENERATION: Custom data analysis software was programmed and executed
in a Macintosh PC to process the TOMS and TOVS databases (each
approximately 500 Mbytes).  For quality control, multi-panel images of
daily measurements of the global ozone distribution were derived from
two independent satellite systems.  NCSA Image and/or Spyglass View
have been used to animate the daily images, providing quality control
and exciting animation.

Researchers

Fritz Hasler, Dennis Chesters 

   NASA, Goddard Space Flight Center, 
   Laboratory for Atmospheres, Greenbelt, 
   MD 20771, (301) 286-9007, 

References

Comparison between TOMS, TOVS and DOBSON observations: satellite and
surface views of total column ozone, by Dennis Chesters and Arthur
Neuendorffer, in Palaeogeography, Palaeoclimatology, Palaeoecology
(Global and Planetary Change Section), vol.  90, pp 61-67, 1991,
published by Elsevier Science Publishers B.V., Amsterdam, The
Netherlands.  

COPYRIGHT: U.S.  government civilian research data is
public domain.  NCSA copyright permission granted.