Τίτλος:
The extraordinary events of the major, sudden stratospheric warming, the
diminutive antarctic ozone hole, and its split in 2002
Περίληψη:
Goal, Scope and Background. Great interest in the unprecedented events
of the major, sudden stratospheric warming and the ozone hole split over
Antarctica in September 25, 2002 motivates a necessity to analyze the
current understanding on the dynamics, chemistry and climate impacts
that are associated with both events.
Methods. Significant progress in the analysis of the observational data
obtained, as well as successful development and application of dynamical
modeling, which have been achieved very recently, create a basis for the
first survey on the role of the major, sudden stratospheric warming
observed in the southern hemisphere and its relationship to the
diminutive Antarctic ozone hole and its break up into two parts.
Results and Discussion. Special attention has been paid to assessments
of the causes of the major warming event and the future expectations
concerning the stratospheric ozone depletion effect. Among the principal
results is the fact that, as the polar vortex elongated, it became
hydrodynamically unstable, and this instability affected the upper
troposphere and stratosphere. During the major, sudden stratospheric
warming, the middle stratospheric vortex split into two pieces; one
piece rapidly mixed with extra vortex air, while the other returned to
the pole as a much weaker and smaller vortex. The polar night jet was
considerably weaker than normal, and was displaced more poleward than
has been observed in previous winters, resulting from a series of wave
events (propagated from the troposphere) that took place over the course
of the winter. Finally, the relative ozone decrease (increase) in the
eastern Antarctic is tightly associated with westerly (easterly) zonal
wind anomalies near the southern tip of South America, and the unusual
behavior of the ozone hole in 2002 therefore appears to be caused by
great easterlies in this region.
Conclusions. The main conclusion is that the southern polar vortex and
the diminutive ozone hole split into two parts in September 2002, due to
the prevalence of very strong planetary waves, led to the appearance of
a major, sudden stratospheric warming. Although there is evidence that
sea surface temperature anomalies contributed to the excitation of the
quite strong planetary waves over Antarctica in 2002, there is not yet a
widely approved mechanism supporting that.
Recommendations and Outlook. The appearance of the near-record size of
the 2003 ozone hole confirmed that the ‘no-ozone-hole’ episode observed
in the year 2002 does not denote a recovery of the ozone layer. Despite
the current successful attempts to get a sufficient understanding for
the genesis of both extraordinary events, more observations and further
modeling efforts are necessary to mote reliably assess the contribution
of various dynamic mechanisms to the recently observed
tropo-stratospheric surprises.
