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10 But I heard that Dobson saw an ozone hole in 1956-58...




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This article is from the Ozone Depletion: The Antarctic Ozone Hole FAQ, by Robert Parson rparson@spot.colorado.edu with numerous contributions by others.

10 But I heard that Dobson saw an ozone hole in 1956-58...

This is a myth, arising from a misinterpretation of an out-of-
context quotation from a review article by Dobson.

In his historical account [Dobson 1968b], Dobson mentioned that
when springtime ozone levels over Halley Bay were first measured,
he was surprised to find that they were about 150 DU below
corresponding levels (displaced by six months) in the Arctic.
Springtime arctic ozone levels are very high, ~450 DU; in the
Antarctic spring, however, Dobson's coworkers found ~320 DU, close
to winter levels. This was the first observation of the _normal_,
pre-1980 behavior of the Antarctic ozone layer: because of the
tight polar vortex (see below) ozone levels remain low until late
spring. In the Antarctic ozone hole, on the other hand, ozone
levels _decrease_ from these already low values. What Dobson
describes is essentially the _baseline_ from which the ozone hole
is measured. [Dobson 1968b] [WMO 1989]

For those interested, here is how springtime antarctic
ozone has developed from 1956 to 1995:

..............................................................
Halley Bay Antarctic Ozone Data

Mean October ozone column thickness, Dobson Units,
as measured at the British Antarctic Survey station
at Halley Bay (Latitude 76 south, Longitude 26 west)

    1956      321          1971      299 	  1986      248 
    1957      330          1972      304          1987      163   
    1958      314          1973      289          1988      232   
    1959      311          1974      274          1989      164   
    1960      301          1975      308          1990      179   
    1961      317          1976      283          1991      155   
    1962      332          1977      251          1992      142   
    1963      309          1978      284          1993      111   
    1964      318          1979      261          1994      124   
    1965      281          1980      227          1995	    129
    1966      316          1981      237          1996	    139 
    1967      323          1982      234          1997      139
    1968      301          1983      210           
    1969      282 	   1984      201 
    1970      282 	   1985      196 

Data from J. D. Shanklin, British Antarctic Survey, personal
communications, 1993-95. For published graphs, see
[Jones and Shanklin], [Hamill and Toon], [Solomon], or
[WMO 1991], p. 4.6. The original Farman et al. figure, which
includes the years 1957-84, is available on the web at
http://www.atm.ch.cam.ac.uk/images/easoe/total_ozone.gif
An updated version can be found on the British Antarctic Survey
web site: http://www.nbs.ac.uk/public/icd/jds/ozone/
Bulletins showing daily ozone measurements at Halley Bay and
at Faraday Station can also be obtained through this web site.

 

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