Τίτλος:
OBSERVATIONAL EVIDENCE FOR CHEMICAL OZONE DEPLETION OVER THE ARCTIC IN
WINTER 1991-92
Γλώσσες Τεκμηρίου:
Αγγλικά
Περίληψη:
LONG-TERM depletion of ozone has been observed since the early 1980s in
the Antarctic polar vortex, and more recently at midlatitudes in both
hemispheres, with most of the ozone loss occurring in the lower
stratosphere(1). Insufficient measurements of ozone exist, however, to
determine decadal trends in ozone concentration in the Arctic winter.
Several studies of ozone concentrations in the Arctic vortex have
inferred that chemical ozone loss has occurred(2-11); but because
natural variations in ozone concentration at any given location can be
large, deducing long-term trends from time series is fraught with
difficulties. The approaches used previously have often been indirect,
typically relying on relationships between ozone and long-lived tracers.
Most recently Manney et al.(11) used such an approach, based on
satellite measurements, to conclude that the observed ozone decrease of
about 20% in the lower stratosphere in February and March 1993 was
caused by chemical, rather than dynamical, processes. Here we report the
results of a new approach to calculate chemical ozone destruction rates
that allows us to compare ozone concentrations in specific air parcels
at different times, thus avoiding the need to make assumptions about
ozone/tracer ratios. For the Arctic vortex of the 1991-92 winter we find
that, at 20 km altitude, chemical ozone loss occurred only between early
January and mid February and that the loss is proportional to the
exposure to sunlight. The timing and magnitude are broadly consistent
with existing understanding of photochemical ozone-depletion processes.
Συγγραφείς:
VONDERGATHEN, P
REX, M
HARRIS, NRP
LUCIC, D
KNUDSEN, BM
and BRAATHEN, GO
DEBACKER, H
FABIAN, R
FAST, H
GIL, M
and KYRO, E
MIKKELSEN, IS
RUMMUKAINEN, M
STAHELIN, J and
VAROTSOS, C
Εκδότης:
Nature Publishing Group
