British Antarctic Survey
Total ozone values are declining from their winter values at Halley and Vernadsky as the ozone hole develops. The next bulletin will be issued in late September.
1. Data from the British Antarctic Survey (BAS) Halley station (76-deg south, 26-deg west, on the Brunt ice shelf).
a) Ozone. Total ozone values from a few low accuracy moon observations were at an estimated 220 DU in early August. This is well below the long-term mean, with depletion around 25%.
Halley preliminary mean daily total ozone, (DU)
Dobson No 103: Instrument constants revised 1998 April 6.
(0 indicates no data)
1998 August 1 - 1998 August 10
b) Radiosonde data. Data from Halley show that the mean 100 hPa temperature is at normal winter values near –84 deg C. Stratospheric clouds, which are instrumental in the mechanism of ozone depletion, were observed from the station on May 27, June 18, 19, 20, 21, 22, 23, 25, 26, 29, July 18, 23, 26, 27, 28, 29 and 30. The displays after July 18 showed similar features to those seen in noctilucent clouds.
Data from the British Antarctic Survey (BAS) Rothera station (68-deg south, 68-deg west on Adelaide Island).
a) Ozone. Ozone measurements from Rothera are made using a SAOZ (Systeme d'Automatique Observations Zenithales) spectrometer. This is a research instrument, but the daily ozone values are available. These show a generally similar pattern of variation to that seen at Vernadsky, though day to day variation is a little less and minimum values are a little lower.
Rothera preliminary mean daily total ozone, (DU)
(0 indicates no data or data not available)
1998 July 1 - 1998 August 22
241 277 293 308 294 281 294 307 299 282
285 297 276 290 298 282 278 280 0 0 289
284 274 282 213 221 246 305 312 261 236
264 248 233 211 247 241 240 269 259 232
Running mean total ozone values fell from an estimated 280 DU in late July to 240 DU in mid August. Values are still declining, and are already over 20% below the long term mean. Day to day variation is currently around 20 DU.
Vernadsky preliminary mean daily total ozone (DU).
Dobson No 31: Instrument constants revised 1998 April 3
1998 August 1 - 1998 August 19
TOVS satellite images from the US NCEP/NWS/NOAA Climate Prediction Center and EP/TOMS images from the US NASA/GSFC show the development of the ozone hole, which is currently somewhat elliptical and shows lowest values over the base of the Antarctic Peninsula. 50 hPa temperatures are below the stratospheric cloud threshold over most of Antarctica.
Further information is available on the BAS ozone web page, which contains earlier bulletins, data, graphs and general ozone information. The url is:
http://www.nbs.ac.uk/public/icd/jds/ozone
Note that all ozone values in this bulletin are preliminary and are subject to revision from time to time when the instrument constants are re-evaluated. Final data will be archived with WOUDC, Toronto in due course, but preliminary data back to 1973 are available from BAS on request. All Dobson ozone data is reduced to the Bass-Paur scale as recommended by the WMO. If you use or pass on this data please make acknowledgement to J D Shanklin, British Antarctic Survey.
Jon Shanklin