The 1999 ozone hole is forming and now covers all of Antarctica with minimum ozone values decreasing steadily.
Lowest values are currently over the Antarctic Peninsula and West Antarctica.
Ozone measurements have only just begun at Halley and are of low accuracy. Measurements made at the start of the season are of lower accuracy than in mid summer due to the low solar elevation or use of moonlight. Gif images showing the data are available on the BAS ozone web-page. Data from Halley show that the mean 100 hPa temperature remains below -80 deg C and is close to normal. Stratospheric clouds, which are instrumental in the mechanism of ozone depletion, were observed from the station on July 19. 2.