Essential characteristics of the Antarctic‐Spring Ozone Decline: Update to 1998

Using both ground‐based and satellite data up to December 1998, the intensity, duration, appearance at both horizontal and vertical scales and ozone‐mass deficiency (O 3 MD) of the severe ozone decline observed over the southern polar region are presented. Over the last six years: the depletion within the ozone hole area (i.e. total ozone amounts <220 m atm‐cm) is almost three times more severe than in the early 1980s, the ozone hole (O 3 h) area has exceeded 22 million km² at its maximum, and the lowest total ozone was ∼100 m atm‐cm. However, during the 1998 season for the first time for nearly 20 days the O 3 h area exceeded 25 million km², and the integrated O 3 MD during September‐October, poleward of 60°S, exceeded the average value of the 1990s by ∼25%. At the beginning of the 1980s, ozone hole values were observed mostly in October, but more recently, they frequently continue until mid‐December. The depletion was most severe in the 12–20 km layer over Antarctica: ∼70% in September, ∼90% in October and ∼80% in November. Related to this, the monthly mean lower stratospheric temperatures between 70–90°S have declined by ∼10°C in October, ∼12°C in November and by ∼5°C in December. Taking the last six years seasonally integrated O 3 MD over the area poleward of 60°S (average ∼6.300 Mt) is about a third greater than the O 3 MD over the northern polar region winter‐springs. Over the southern mid‐latitudes O 3 MD is about a third less than the deficiency observed between 35–55°N.