BAS Ozone Bulletin 03/00
The 2000 ozone hole reached its greatest extent in early
September at 28.4 million square kilometres and was the largest
ever-recorded ozone hole. It reached this maximum extent
unusually early, as the hole is normally largest in late
September. Minimum ozone values were measured in early October
and were amongst the lowest on record. The edge of the ozone hole
passed over the tip of South America and the Falkland Islands for
significant periods between October 6 and 24. The hole also
closed in unusually early and the event was essentially over by
early December.
Satellite imagery gives a global perspective on the ozone hole. TOVS and TOMS currently have significantly different calibrations, with TOVS reading some 40 DU higher than TOMS. TOMS values are close to ground-based values. Our 2000/2001 ozone hole movie, produced from TOMS images, is generally updated every week. Stratospheric clouds were sighted from Vernadsky, Rothera and Halley. A mini ozone hole, with central values below 200 DU, periodically formed to the east of the Antarctic Peninsula over the Weddell Sea during July. This mini ozone hole probably formed due to processing of ozone through PSCs, which are far enough north to be sunlit. The feature was particularly marked on July 10 and again on July 20.
Ozone values over the Arctic are normally at their lowest in September and this year was no exception as can be see from the TOMS images. Although the values were low, they were low because of stratospheric dynamics and not chemistry. The temperature in the Arctic ozone layer was above -55°C, far too warm for stratospheric clouds to form. Hence there was no chemical depletion taking place and no ozone hole above the Arctic. In mid October there were regions of low ozone over Siberia. Stratospheric temperatures in this area were generally above -65°C, so again these features had a dynamic, not chemical origin. Arctic stratospheric temperatures in late January are well below the threshold for PSC formation in a small region between Greenland and Siberia. This region has ozone values lower than elsewhere in the Arctic, but still above 300 DU.
1. Data from the British Antarctic Survey (BAS) Halley station
(76-deg south, 27-deg west, on the Brunt ice shelf).
Halley preliminary mean daily total ozone, (DU)
Dobson No 103: Instrument constants revised 1999 October 8.
(0 indicates no data)
2000 August 1 - 2001 January 18
0 0 0 0 0 0 0 0 0 201
151 174 182 0 0 165 153 149 0 0
0 0 0 0 0 0 255 188 165 180 179
189 184 196 192 199 206 183 167 152 170
172 165 167 155 138 143 152 129 127 123
135 134 129 129 120 110 121 114 108 107
118 119 120 124 112 112 105 120 119 119
121 131 135 125 119 123 129 141 139 138
138 150 160 159 154 168 164 173 171 164 164
188 241 267 271 235 205 261 279 295 292
284 284 285 280 293 302 321 300 264 278
247 279 292 283 271 236 220 227 248 281
307 305 330 323 316 317 317 322 329 316
301 292 299 294 300 318 299 296 287 298
300 293 285 277 283 276 273 271 274 290 293
286 282 288 0 0 0 0 0 0 0
292 291 274 278 272 286 307 279
Halley provisional monthly mean total
ozone (DU)
Period Aug Sep Oct Nov Dec Jan
Feb Mar Apr Year
2000/01 179 151 137 267 299
1999/00 205 172 143 172 254 281 258 250 256 221
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
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.
2. Data from the British Antarctic Survey (BAS) Rothera
station (68-deg south, 68-deg west on Adelaide Island).
2000 July 1 - 2001 February 5
273 249 276 0 0
288 236 205 144 173 225 279 264 245 225 232 243 225 201
246 225 178 213 201 225 233 245 0 242 220 246 232 211 228
203 228 240 231 246 246 286
298 252 226 217 238 241 0 0 188 196
179 175 184 220 193 232 262 287 273 258 202
195 208 193 184 187 162 127 111 114 108
138 128 121 115 0 0 124 111 94 92
104 119 101 98 111 120 110 127 198 225
189 149 136 124 120 125 137 134 139 0
0 105 100 112 117 110 104 114 119 130
124 139 164 260 234 259 296 327 244 259 299
0 353 355 365 355 355 353 361 354 339
335 323 337 357 0 342 338 328 334 354
351 336 308 308 299 291 307 307 303 305
277 292 300 0 326 329 319 302 293 298
307 304 296 293 283 288 292 291 292 293
290 292 296 296 290 279 280 287 279 267 274
274 279 292 287 282 279 289 286 273 268
266 270 273 272 271 272 275 262 0 257
256 256 259 268 278 270 274 272 273 270 273
301 295 292 302 296
Rothera provisional monthly
mean total ozone (DU)
Period Jul Aug
Sep Oct Nov Dec Jan Feb Mar Apr May Jun
2000/01 231 230 137 168 334 294 273
1999/00 274 243 157 175 229 289 282 265 264 290 282 293
1998/99 288 239 159 166 252 264 270 279 267 277 300 287
1997/98 270 280 267 263
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).
2000 August 1 - 2001 February 6
255 245 265 236 248 263 252 246 246 286
277 255 213 213 229 252 245 205 214 207
198 192 204 238 196 219 258 291 316 298 242
239 237 213 209 195 177 148 141 142 147
164 138 130 145 141 164 160 133 119 118
120 158 134 139 149 148 131 157 187 271
259 245 225 169 161 160 156 158 187 139
132 128 121 132 138 144 131 130 145 155
144 149 180 240 269 260 304 358 292 285 297
344 354 367 357 372 378 374 370 364 359
336 330 321 367 344 351 347 348 333 348
361 364 324 327 317 295 313 321 306 312
299 312 329 315 327 329 323 316 308 311
311 305 298 297 309 293 307 289 295 299
298 318 302 324 312 306 304 300 304 294 301
310 316 317 311 291 277 292 276 280 281
292 296 288 300 288 295 303 288 281 282
284 276 286 301 301 296 296 305 295 284 304
312 304 309 309 298 287
Vernadsky provisional monthly
mean total ozone (DU)
Period Aug Sep Oct Nov
Dec Jan Feb Mar Apr Year
2000/01 242 162 193 343 308 293
1999/00 249 189 202 283 297 292 271 262 293 260
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
1957-72 310 330 345 370 345 320 300 295 310 325
4. Information from other sources.
The use of data from TOVS satellite images from the US
NCEP/NWS/NOAA Climate Prediction Center and EP/TOMS images is
acknowledged.
Further information is available on the BAS ozone web page, which
contains earlier bulletins, data, graphs and general ozone
information. It is often updated several times a week during the
ozone hole period. The email ozone bulletins have been issued
less frequently this year so for the latest information see:
http://www.antarctica.ac.uk/met/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 are
reduced to the Bass-Paur scale as recommended by the WMO. The
reference period used for the normals is 1957 - 1972. If you use
or pass on data in this bulletin please make acknowledgement to J
D Shanklin, British Antarctic Survey.