British Antarctic Survey

BAS Ozone Bulletin 07/98 issued 1999 May 13

The 1998 Antarctic ozone hole was broadly similar to those seen in recent years, although a little larger and a little longer lasting. At Halley the final spring warming did not take place until late December and a remnant of the ozone hole passed over the station in late January.

The first bulletin of the 1999/2000 season will be issued in late August.

1. Data from the British Antarctic Survey (BAS) Halley station (76-deg south, 26-deg west, on the Brunt ice shelf).

Ozone. Mean total ozone values declined from around 260 DU in early August to a minimum of 120 DU in early October at a rate of around 3 DU per day. They rose a little, but oscillated around 180 DU from late October until the final warming began in early December. Peak ozone values of around 290 DU occurred in late December, but this was nearly a month later and 25% lower than the historical maximum. Values slowly declined from this peak through the rest of the summer. Unusually low ozone values and 100 hPa temperatures were recorded around January 21 when a remnant of the ozone hole passed over the station. Autumn values were around 260 DU, some 15% below normal.

Halley preliminary mean daily total ozone, (DU)
Dobson No 103: Instrument constants revised 1998 November 13.
(0 indicates no data)

1998 August 1 - 1999 April 30

0 0 238 232 232 0 0 0 0 225 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 244 216 240 178 184 177 180 191 186 192 217 225 223 197 195

158 157 165 141 148 188 199 174 145 122

126 142 146 117 119 110 105 143 136 125

119 112 124 109 111 111 109 118 125 130

127 121 119 117 127 142 143 150 149 145

134 129 129 136 139 162 219 183 183 211 212

209 213 173 187 189 166 157 154 138 147

152 177 204 192 192 182 195 177 199 210

238 239 200 177 171 172 182 172 165 175

177 228 271 248 226 211 198 190 210 230

225 261 251 247 240 237 263 269 277 260

280 294 299 300 296 296 298 290 276 268 285

289 285 277 284 289 285 291 269 275 278

263 272 299 260 256 260 260 262 278 241

237 248 264 290 270 258 257 270 284 296 272

268 255 281 259 252 248 253 265 269 256

257 266 270 272 269 260 252 248 251 252

263 271 265 245 259 260 234 257

256 246 235 246 242 242 248 241 238 242

261 258 265 260 256 264 267 283 277 294

262 208 219 256 236 250 238 265 275 272 282

253 256 243 247 237 266 280 0 0 0

0 0 0 0 0 0 0 0 0 0

Halley provisional monthly mean total ozone (DU)

Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1998/99 221 162 140 183 255 272 259 254 267 224
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.

Radiosonde data. Data from Halley show that the mean 100 hPa temperature remained below -80 deg C until mid October. The spring warming was very late, with maximum temperatures not reached until late December and then 2 deg C below the historic average. The 100 hPa temperature remained significantly below average until April. Particularly noteworthy was the period around January 21 when the lowest January 100 hPa temperature on record was observed.

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, September 1 and October 19. The displays in July showed similar features to those seen in noctilucent clouds.

2. Data from the British Antarctic Survey (BAS) Rothera station (68-deg south, 68-deg west on Adelaide Island).

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 and do not show such pronounced wave activity. Very low values were recorded several times between mid September and mid October.

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

1998 July 1 - 1999 April 30

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

152 162 138 142 150 127 181 204 128 115

107 115 131 146 140 162 182 152 123 126

121 0 0 167 168 146 134 118 111 102

102 114 151 251 258 268 245 233 244 252 239

231 236 0 271 250 168 170 198 186 180

268 319 334 332 264 226 225 217 318 317

330 297 234 203 244 264 252 246 256 274

244 159 165 172 176 176 195 209 0 295

292 303 302 271 241 256 282 304 312 320

320 313 305 296 288 282 273 291 304 290 278

0 272 273 263 264 269 270 276 283 268

278 280 287 284 269 259 258 255 258 273

278 273 288 280 277 280 275 257 254 249 250

258 270 278 273 278 273 275 0 0 0

264 271 277 264 276 281 284 293 279 277

279 290 309 301 0 284 298 264

270 259 254 257 260 265 276 284 294 274

281 291 282 284 294 289 284 273 0 267

277 250 226 242 243 246 241 252 257 265 263

249 258 265 271 262 287 296 303 304 323

303 301 328 0 0 262 256 264 295 305

305 248 260 262 257 228 258 269 278 263

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

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, September 16, 17, 18.

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).

Ozone. Running mean total ozone values fell from an estimated 280 DU in late July to 180 DU in early September. Strong long period wave activity with a period of about a month gave a variation of around 25 DU on this mean value (50 DU on daily values) until late October when a major warming event occurred and values rose above 320 DU. Values dropped again in early November and early December as the vortex rotated. Mean ozone values then remained around 280 DU (10 - 15% below normal) for the rest of the season, with long period wave activity building again from mid February.

Vernadsky preliminary mean daily total ozone (DU).
Dobson No 31: Instrument constants revised 1999 May 10

1998 August 1 - 1999 April 30

272 265 281 249 220 253 288 295 270 237

234 233 226 212 224 251 220 259 251 244

231 201 229 197 199 208 266 225 262 243 211

253 240 261 212 222 198 185 201 187 188

197 184 201 182 146 132 156 149 240 164

186 293 213 236 221 167 214 240 188 155

139 158 149 178 180 196 249 258 161 163

151 177 207 245 246 212 229 167 156 132

136 136 162 257 298 317 344 333 339 351 338

315 309 302 341 324 238 221 255 250 185

289 365 342 358 315 289 297 298 350 338

363 383 275 260 307 308 317 308 320 330

297 244 197 188 215 197 197 224 280 310

325 317 317 296 266 263 302 300 322 317

325 308 311 293 297 276 289 289 298 280 286

284 300 288 277 287 302 309 309 310 267

296 292 294 304 287 281 277 279 279 275

275 273 287 297 290 289 297 277 285 274 272

276 279 295 290 288 286 285 285 288 279

281 279 280 280 299 275 292 297 288 302

292 281 316 310 312 276 306 278

250 265 260 274 267 269 267 273 304 269

279 287 285 289 291 297 307 284 290 290

286 274 238 232 249 264 239 246 256 292 283

242 240 261 278 262 292 301 298 301 319

327 307 342 313 278 272 271 266 307 261

303 258 251 271 263 233 255 270 272 251

Vernadsky provisional monthly mean total ozone (DU)

Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1998/99 241 200 218 305 278 288 289 273 279 263
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

Radiosonde data. Radiosonde flights at Bellingshausen and Marambio show that the 100 hPa temperature oscillated near winter values of around -75 deg C until October 24, when the initial spring warming occurred. Further periods of low 100 hPa temperature were recorded around November 9 and December 4. Summer values oscillated around -46 deg C, a few degrees below normal. The 100 hPa temperature was generally below average from October to March. 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 formation and decline of the ozone hole. The edge of the ozone hole crossed over the tip of South America around September 7, 18, October 1, 11, November 10 and December 4. The area was more severely affected from October 19 to 23 and December 7 to 11, on the later occasion significant ozone depletion reaching as far as 40 South. The hole covered an area of around 27 million square kilometres at its largest, which is larger 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