Cs. Zerefos et al., FURTHER-STUDIES ON POSSIBLE VOLCANIC SIGNAL TO THE OZONE-LAYER, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 99(D12), 1994, pp. 25741-25746
This paper provides a new look at the spatial and temporal distributio
n of monthly mean residuals of the global ozone field following the tw
o large volcanic eruptions of El Chichon and Pinatubo. The residuals h
ave been calculated after careful removal of the components of known o
scillations from the monthly mean total ozone records. The removal eli
minated not only the well-established Quasi Biennial Oscillation but a
lso the robust pattern of all El Nino/Southern Oscillation events acti
ve during the period of study. These residuals are composed by a ''cli
matic noise'' term plus a possible volcanic signal whose amplitude is
in some agreement with model calculations particularly over low and mi
ddle latitudes following the recent Pinatubo eruption. However, this a
nalysis shows no ozone deficiency following El Chichon over the southe
rn hemisphere and this result can be explained by the prevailing winds
in the lower stratosphere in the post-El Chichon period as described
in the text. Quantitatively speaking, the magnitude of the observed oz
one deficiency which can be attributed to the volcanic effect is small
er than reported earlier either from theory or observations, and range
s between 2 and 4% at the equatorial latitudes up to about 5% over the
middle and high latitudes, including the noise term, and lasting for
a period of months after the eruption. These deficiencies are also lar
ger than the anticipated error caused by the aerosol-contaminated radi
ances, as reported by other scientists. The present results, although
not precluding a transient volcanic component following large volcanic
eruptions in the ozone records, do show, however, that our understand
ing of the physical mechanisms involved is probably still incomplete.