Rd. Bojkov et al., TOTAL OZONE TRENDS FROM QUALITY-CONTROLLED GROUND-BASED DATA (1964-1994), JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 100(D12), 1995, pp. 25867-25876
Seasonal and year-round trend analyses of ground-based total ozone dat
a that have been carefully quality controlled are presented for 46 Dob
son stations, for four regions of the former USSR and for the two pola
r regions. The trend model incorporated the 10.7-cm solar flux and equ
atorial stratospheric wind as indicators for removal of the solar and
quasibiennial components in ozone variations. The trends were calculat
ed for two main time intervals: from January 1964 through March 1994,
with slope since 1970, and from January 1979 through March 1994. The a
nalyses show continuous year-round ozone decline in middle latitudes (
35 degrees-60 degrees) where the estimated values are -4.3 and -4.1% p
er decade for the period since January 1979 in the northern and southe
rn hemispheres respectively. The northern hemisphere data permit estim
ation of the trends over vast regions such as North America -4.1+/-1.5
%, Europe -5.1+/-2.0%, Siberia and Far East -5.6+/-1.8% (values and tw
o sigma intervals are given in percent per decade for year-round trend
). The ozone decline over the Arctic is about -5.6+/-2.0% per decade f
or year-round trend and -7.5+/-3.8% for the winter-spring season. The
most dramatic ozone decline occurs in spring over Antarctica, -22+/-7.
2% per decade. The trends estimated for the 1979-1994 period are about
1.5% per decade stronger in northern and southern middle and high lat
itudes than the trends with slope since 1970, which shows a substantia
l acceleration of the rates of ozone decline. The sensitivity of the o
zone trends to the extremely low ozone during the 1992-1993 period is
discussed. Most of the ozone data and calibrations in this paper were
the base for the Ozone Trends section of the World Meteorological Orga
nization/United Nations Environment Program Ozone Assessment 1994. The
results presented here in general concur with the assessment and prov
ide further estimates of the ozone changes in the northern middle lati
tudes in view of another extremely low winter-spring season of 1994-19
95.