Ch. Jackman et al., PAST, PRESENT, AND FUTURE MODELED OZONE TRENDS WITH COMPARISONS TO OBSERVED TRENDS, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 101(D22), 1996, pp. 28753-28767
The NASA Goddard Space Flight Center (GSFC) two-dimensional (2-D) mode
l of stratospheric transport and photochemistry has been used to predi
ct ozone changes that have occurred in the past 20 years from anthropo
genic chlorine and bromine emissions, solar cycle ultraviolet flux var
iations, the changing sulfate aerosol abundance due to several volcani
c eruptions including the major eruptions of El Chichon and Mount Pina
tubo, solar proton events (SPEs); and galactic cosmic rays (GCRs). The
same linear regression technique has been used to derive profile and
total ozone trends from both measurements and the GSFC model. Derived
2-D model ozone profile trends are similar in shape to the Solar Backs
cattered Ultraviolet (SBUV) and SBUV/2 trends with highest percentage
decreases in the upper stratosphere at the highest latitudes. The gene
ral magnitude of the derived 2-D model upper stratospheric negative oz
one trend is larger than the trends derived from the observations, esp
ecially in the northern hemisphere. The derived 2-D model negative tre
nd in the lower stratosphere at middle northern latitudes is less than
the measured trend. The derived 2-D model total ozone trends are smal
l in the tropics and larger at middle and high latitudes, a pattern th
at is very similar to the Total Ozone Mapping Spectrometer (TOMS) deri
ved trends. The differences between the derived 2-D model and TOMS tre
nds are generally within 1-2% in the northern hemisphere and the tropi
cs. The derived 2-D model trends are generally more in southern middle
and high latitudes by 2-4%. Our 2-D model predictions are also compar
ed with the temporal variations in total ozone averaged between 65 deg
rees S and 65 degrees N over the TOMS observing period (1979-1993). In
clusion of anthropogenic chlorine and bromine increases, solar cycle u
ltraviolet flux variations, and the changing sulfate aerosol area abun
dance into our model captures much of the observed TOMS global total o
zone changes. The model simulations predict a decrease in ozone of abo
ut 4% from 1979 to 1995 due to the chlorine and bromine increases. The
changing sulfate aerosol abundances were computed to significantly af
fect ozone and result in a maximum decrease of about 2.8% in 1992 in t
he annually averaged almost global total ozone (AAGTO) computed betwee
n 65 degrees S and 65 degrees N. Solar ultraviolet flux variations are
calculated to provide a moderate perturbation to the AAGTO over the s
olar cycle by a maximum of +/-0.6% (about 1.2% from solar maximum to m
inimum). Effects from SPEs are relatively small, with a predicted maxi
mum AAGTO decrease of 0.22% in 1990 after the extremely large events o
f October 1989. GCRs are computed to cause relatively minuscule variat
ions of a maximum of +/-0.02% in AAGTO over a solar cycle.