British Antarctic Survey

British Antarctic Survey
Ozone Bulletin 17/97 issued 1998 February 6

Total ozone values are slowly declining at Halley and Vernadsky following the spring peak and have remained 15 - 20% below the long term mean. The January mean for Vernadsky is the lowest on record, and that for Halley equals the record low of 1995. The 100 hPa temperature over both stations is significantly below the long term mean. The next bulletin will be issued in May.

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 fell from an estimated 300 DU in early July to around 200 DU in mid August. Values rose to around 240 DU towards the end of August but then steadily fell to reach 115 DU in early October. Ozone values rose to around 160 DU late in October and remained near this value until mid November when the spring warming started. Values peaked at just under 300 DU in early December, compared to the long term mean peak of 380 DU. Since then values have declined to around 260 DU. This is well below the long-term mean, with depletion over 15%. Day to day variation is now around 20 DU.

Halley preliminary mean daily total ozone, (DU)
Dobson No 103: Instrument constants revised 1998 February 4.
(0 indicates no data)

1997 August 1 - 1998 February 5

0 0 0 0 0 0 0 0 0 0

194 0 194 196 213 214 221 215 230 217

0 0 0 0 0 0 217 247 206 190 183

175 188 182 182 216 215 207 192 171 184

190 168 170 157 181 179 147 154 168 174

163 156 139 134 130 142 147 131 123 125

155 127 117 123 122 118 116 116 126 115

115 118 129 122 118 122 124 145 149 164

165 153 175 189 179 167 164 154 148 143 158

154 146 156 154 173 162 162 165 161 160

162 160 163 183 182 189 203 228 240 251

262 263 243 235 261 268 277 301 282 265

272 278 274 291 301 307 293 295 311 293

300 289 298 302 276 250 243 279 286 295

284 294 289 281 276 271 269 262 272 274 280

280 278 280 267 270 263 263 248 247 254

256 258 254 266 274 259 255 277 292 254

248 248 259 276 272 278 255 250 259 256 247

241 257 257 264 254

Halley provisional monthly mean total ozone (DU)

Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1997/98 210 166 140 207 283 263
1996/97 172 155 149 181 260 278 265 245 242 216
1995/96 219 160 129 163 253 263 248 247 224 210
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 rose from winter values of -83-deg C in mid October and reached a plateau at -75-deg C by the end of the month. The rapid spring warming began in mid November, and peaked at -42-deg C in early December. The 100 hPa temperature has remained significantly below the long term mean all summer. Stratospheric clouds, which are instrumental in the mechanism of ozone depletion, were observed from the station on August 1, 3, 6, 7, 8, 10, 13, 14, 15, September 3, 4, 21, 22, 26, 27, 30 and October 2, 3, 6 and 7. The display on August 10 was particularly vivid and that of September 30 showed classic development after sunset. The display on October 2 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)

1997 August 1 - 1998 February 2

299 216 227 199 239 211 218 299 285 270

301 297 309 312 304 266 279 272 256 259

259 294 287 292 266 266 297 304 295 270 236

230 199 214 248 259 244 216 194 204 203

200 196 172 205 283 338 351 359 330 297

257 200 193 241 216 186 206 204 201 211

181 159 152 133 131 145 157 153 133 136

120 137 134 138 153 187 199 222 290 346

357 329 348 360 340 324 284 201 156 153 142

130 133 150 157 168 183 157 155 145 146

141 150 153 175 186 218 238 271 312 323

314 318 306 275 278 321 310 310 299 302

292 280 284 284 285 293 291 301 308 310

309 309 304 294 283 290 295 292 287 279

276 274 282 291 288 285 281 278 276 0 0

282 283 278 284 287 288 280 284 280 283

276 280 278 265 237 257 255 254 257 255

242 244 249 250 255 262 264 256 257 251 250

246 256

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 8, 10, 13, 15, July 4, 17, 21, 23, August 4, September 1, 3 and October 14.

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 350 DU in early July to 240 DU in early August. From then until early December the running mean varied between 150 and 340 DU (55% - 5% depletion) under the influence of strong planetary waves with a period of around a month. The spring warming produced a peak of around 320 DU, which is 20% below the long term mean. Values are now slowly declining, and are still 15% below the long term mean. Day to day variation is currently around 20 DU. Particularly low values were recorded on August 2^nd, when the station was affected by one of the ozone reduction events associated with the forming ozone hole. Very low values occurred around September 13^th, October 4^th, 11^th and November 1^st (142 DU is the lowest November daily mean on record for the station) when the centre of the ozone hole passed near the station. Very high values near 370 DU were recorded on September 18^th and October 21^st when the circumpolar high ozone belt was over the station.

Vernadsky preliminary mean daily total ozone (DU).
Dobson No 31: Instrument constants revised 1997 December 5

1997 August 1 - 1998 February 4

271 212 234 227 231 232 232 283 278 261

256 259 277 287 287 255 241 237 236 250

237 299 293 297 258 289 316 314 307 302 255

236 199 207 257 256 252 234 214 213 210

202 184 154 206 271 356 370 373 372 287

269 214 186 255 250 218 246 263 265 243

227 198 176 150 151 161 201 182 159 170

152 161 158 150 156 194 237 234 330 370

364 356 365 364 343 343 322 275 195 186 172

143 152 164 182 197 229 222 170 164 154

157 169 167 166 188 198 229 278 320 321

319 324 296 295 332 327 315 301 317 308

311 282 280 288 285 286 288 291 297 300

297 310 309 301 285 286 291 290 293 293

289 280 287 287 303 293 304 299 294 286 283

271 280 285 288 288 287 286 294 299 285

284 285 276 273 280 287 277 293 279 287

282 261 248 253 260 266 273 265 264 257 264

248 248 264 277

Vernadsky provisional monthly mean total ozone (DU)

Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1997/98 265 249 232 237 293 277
1996/97 217 205 263 226 271 304 279 277 294 260
1995/96 237 194 251 228 298 285 287 278 266 258
1957-72 310 330 345 370 345 320 300 295 310 325

b) Radiosonde flights at Bellingshausen resumed in mid November and show a rapid rise in temperature at the 100 hPa level, peaking at -44-deg C in mid December. Values are now slowly declining and are significantly below the long term mean for the time of year.

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 and break-down of the ozone hole. Development of stratospheric clouds in lee waves from the Antarctic Peninsula seems to have generated enhanced ozone depletion over the Weddell Sea in a number of events in the early stages of the ozone hole formation. The maximum extent of the ozone hole occurred as usual in the first week of October. Satellite images show that the edge of the ozone hole passed over the tip of South America and the Falkland Islands on September 13/14, October 12/15, October 31/November 5 and November 10/15 and just clipped the area on September 23/24 and October 4/5. The rapid breakdown of the hole commenced in the week of November 17 and ozone values are now declining from their summer high over the Antarctic continent.

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