BAS Ozone Bulletin 03/98 issued 1998 October 2


Total ozone values are near their minimum at Halley and Vernadsky and are broadly comparable with the past few years. The area covered by the ozone hole is larger than that seen recently.


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 have declined from around 260 DU in early August to 120 DU in early October at a rate of around 3 DU per day. Values are well below the long-term mean, with depletion near 60%, but comparable to the past few years. Day to day variation is around 20 DU. The preliminary mean daily value of 107 DU on September 27 is the lowest recorded for September.


Halley preliminary mean daily total ozone, (DU)
Dobson No 103: Instrument constants revised 1998 April 6.
(0 indicates no data)


1998 August 1 - 1998 September 30

0 0 228 222 223 0 0 0 0 217

0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 245 216 241 179 184

174 180 192 185 192 217 224 223 197 194

157 156 164 141 149 187 198 173 146 123

127 141 145 118 118 112 107 143 138 127


Halley provisional monthly mean total ozone (DU)


Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1998/99 217 162
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 or use of moonlight. 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 near or a little below normal winter values at around –81 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, 30, August 9, 27, 31. The displays in July 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. Very low values were recorded in mid September.

Rothera preliminary mean daily total ozone, (DU)
(0 indicates no data or data not available)


1998 July 1 - 1998 September 29


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

0 0 204 184 190 201 237 208 229 204 202

222 210 202 183 206 189 175 188 172 154

165 151 166 142 118 105 105 0 134 122

152 162 138 142 150 127 181 204 132


Note: The instrument calibration is in error by around 15% at 100 DU, reading too low.


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, August 15.


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 190 DU in late September. Values are over 40% below the long term mean, though comparable to the past few years. Day to day variation is currently around 40 DU.


Vernadsky preliminary mean daily total ozone (DU).
Dobson No 31: Instrument constants revised 1998 April 3


1998 August 1 - 1998 September 30


280 274 289 257 228 260 293 301 275 242

238 237 226 215 228 255 221 262 255 247

233 204 232 200 202 211 269 228 265 246 213

256 243 263 215 224 201 187 203 187 0

0 0 0 0 0 0 158 152 243 167

189 295 216 238 224 169 216 242 190 158


Vernadsky provisional monthly mean total ozone (DU)


Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1998/99 245
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 and Marambio show 100 hPa temperatures that are generally close to the seasonal normal. Anomalously low 100 hPa temperatures were recorded at Marambio on September 18. 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. It is currently somewhat elliptical and centred away from the pole towards the Weddell Sea, with the long axis extending to the South American continent. There were low values over the base of the Antarctic Peninsula around September 17, confirming the low Rothera values. The hole covers an area of around 26 million square kilometres, which is larger than in recent years. 50 hPa temperatures are below the stratospheric cloud threshold over a large part of Antarctica, though the area covered by these temperatures is shrinking and warming has occurred over Wilkes Land. UK Met Office analyses show core 100 hPa temperatures below -86 deg C, much lower than in recent years.



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