British Antarctic Survey
Ozone Bulletin 01/98 issued 1998 August 24



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

 0 0 228 222 223 0 0 0 0 217
Halley provisional monthly mean total ozone (DU)


Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1997/98 218 171 141 210 286 267 262 264 261 231
1996/97 173 155 148 181 260 278 265 247 243 217
1995/96 218 160 130 164 252 261 249 246 226 212
1957-72 295 285 300 355 350 320 300 295 285 310

Note that August and April do not have observations on every day, and that the routine measurement season is now longer than it was in 1957 - 72. Measurements made at the start of the season are of lower accuracy than in mid summer due to the low solar elevation. Gif images showing the data are available on the BAS ozone web-page.

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


 277 284 301 288 300 303 0 0 286 284

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


b) Stratospheric clouds. Nacreous or mother-of-pearl clouds are regularly seen from stations along the Antarctic Peninsula between early May and October, with a peak in July. There is some evidence that their frequency of occurrence has increased since the mid 1950s. This year they were observed from Rothera on June 13, 30, July 2, 3, 4, 8.


3. Data from the Ukrainian Antarctic Research Centre Vernadsky station (65-deg south, 64-deg west on the coast of the Antarctic Peninsula, formerly the BAS Faraday station).


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


 280 274 289 257 228 260 293 301 275 242 238 237 226 215 228 255 221 262 255
Vernadsky provisional monthly mean total ozone (DU)


Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1997/98 261 251 235 240 297 281 266 280 281 266
1996/97 208 203 265 225 272 307 281 277 283 258
1995/96 240 199 252 230 296 284 285 276 264 258
1957-72 310 330 345 370 345 320 300 295 310 325

b) Radiosonde flights at Bellingshausen show 100 hPa temperatures that are close to the seasonal normal. Stratospheric clouds were seen from Vernadsky on June 13 and July 14


4. Information from other sources.


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