During late April and most of May 1997 the southern part of South America, ie. Argentina and Chile, were subject to extremely low ozone values in a swath extending from the Pacific and Northern Chile into the South Atlantic, close to the Malvinas Is. In the core of this low ozone region significantly low ozone values were registered for a number of days. These values were below the 220 DU established in the definition of 'ozone' hole. Furthermore the region of low values was quais-stationary. This peculiar situation was associated with a persistant blocking situation that resulted in unseasonally high surface temperatures in the region.
The event is discussed using meteorological analysis data, TOMS total ozone measurements and UARS-HALOE compositional retrievals.
The nature of the low ozone values is discussed ie., dynamical versus chemical causes