BAS Ozone Bulletin 08/99 issued 1999 December 17
The 1999 ozone hole is filling rapidly, though a weak polar vortex is still present. The remains of the hole are centred over Enderby Land and here there is a small area with ozone values below 225 DU. There are high ozone values off the Pacific coast of Antarctica. The edge of the ozone hole crossed the southernmost tip of South America and the Falkland Islands over November 21 to 22. Total ozone values at Halley have risen rapidly in the past few days to 300 DU, though this is still 15% below the normal for mid December. Stratospheric temperatures at Halley are around -45 deg C, a few degrees below the normal for mid December.
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)
1999 August 21 - 1999 December 16
231 211 206 192 205 206 218 201 209 196
185 178 173 169 167 145 140 150 175 177
151 151 199 159 136 121 125 129 125 117
114 116 139 170 162 132 130 137 140 159
142 141 140 139 150 155 132 144 150 155
151 149 153 134 126 129 137 150 147 155 145
153 160 152 158 167 167 160 162 151 152
155 159 166 166 157 166 185 206 217 216
198 181 183 187 176 174 168 165 167 174
183 167 178 195 185 192 207 219 253 261
285 284 289 296 302 313
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.
Stratospheric clouds, which are instrumental in the mechanism of ozone depletion, were observed from the station on July 19, August 13, 14, 15, 18 and September 1, 2, 3, 4, 10, 13, 15, 27, 28, 30.
2. Data from the British Antarctic Survey (BAS) Rothera station (68-deg south, 68-deg west on Adelaide Island).
Rothera preliminary mean daily total ozone, (DU)
(0 indicates no data or data not available)
1999 July 1 - 1999 December 15
298 294 294 293 298 273 247 219 0 211
231 276 279 277 243 224 238 244 265 273 283
299 313 281 270 267 290 0 258 260 260
210 228 239 256 249 243 200 232 262 239
225 222 219 224 241 214 210 210 225 219 223
186 175 0 165 164 194 183 162 158 164
154 143 162 160 184 149 148 163 162 162
159 173 161 166 130 129 119 116 114 0
150 175 192 207 157 274 292 280 279 239
155 151 145 136 126 110 124 124 145 155
151 148 138 0 166 178 172 156 154 164 207
227 204 254 313 320 276 259 236 165 0
188 187 172 193 217 242 282 288 231 191
190 250 289 282 217 162 164 173 220 262
257 198 168 178 240 302 319 322 326 329
327 324 315 313 302
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).
Vernadsky preliminary mean daily total ozone (DU).
Dobson No 31: Instrument constants revised 1999 October 25
1999 August 1 - 1999 December 8
296 319 275 275 282 288 262 253 254 265
229 215 230 268 258 264 219 234 232 226
226 244 226 236 240 206 215 231 261 235 252
219 191 177 186 174 237 224 194 170 182
201 196 174 183 233 199 171 222 208 181
199 215 181 242 161 173 159 142 146 138
145 183 208 250 164 249 309 301 269 280
196 195 187 177 163 145 145 152 182 204
181 180 187 165 178 194 219 206 197 232 229
281 259 261 334 347 308 323 334 252 259
224 275 281 259 328 329 343 347 274 229
206 273 334 343 309 189 213 206 252 307
335 252 209 172 195 289 321 332
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 progressive filling of the ozone hole. The remains of the hole are centred on Enderby Land, with a small area having values below 225 DU. There are high ozone values off the Pacific coast of Antarctica. The margins of the hole briefly crossed the southernmost tip of South America and the Falkland Islands over November 21 to 22. UK Met Office charts show that the 100 hPa temperature remains below -60 deg C in the weakening polar vortex. NOAA analyses show that the 50 hPa temperature has remained below the normal since early June.
An interesting low ozone event in the Northern Hemisphere occurred around November 30th. Nacreous clouds were widely seen over Scotland and very low ozone values measured over the North Sea. These events were associated with unusually low stratospheric temperatures, with chemical depletion playing a minor part in the low ozone values.
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 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.