The total ozone anomaly at Lauder, NZ in 1997

A record low annual mean value of total ozone was observed at Lauder, New Zealand in 1997, namely 294.5 DU, compared to a 1985-96 mean of 307.9+/-3.7. Ozone values were low through most of the year, especially in winter and spring. These observations are similar to TOMS results for Southern mid-latitudes, although the long-term comparison is clouded by the change in TOMS instruments. A regression analysis of the Lauder record through 1996 allows a generally accurate prediction of the 1997 values, shows that the QBO dominates the 1996-97 difference, and that the 1997 values are consistent with a linear long-term trend in ozone. The analysis does not completely explain low monthly values in austral spring; Enhancements in biologically active UV radiation were also observed, with monthly mean values increased by as much as 20-40% from recent years. The unusual ozone values were the dominant cause of the UV enhancement.