BAS ozone bulletin 16/94 issued 1995 May 16. This bulletin gives a resume of the provisional ozone data for 1994/95 from the British Antarctic Survey Faraday station (65 south, 64 west on the coast of the Antarctic Peninsula) and Halley station (76 south, 26 west on the Brunt ice shelf), obtained using the Dobson ozone spectrophotometer. The definitive instrument and zenith calibration values have not yet been determined. A daily mean value is given, using all the observations for that day, assigning equal weight to each. Note that all values are preliminary and are subject to revision from time to time. The final daily values may differ from those given here, but should not differ from them by more than 5%. Some experimental zenith observations at low solar elevations are included, these have lower accuracies than normal observations. Monthly mean values are given for each station with pre ozone hole means for comparison. Preliminary mean ozone values from Faraday show that mean ozone values at the end of the winter were around 290 DU dropping to a minimum of around 160 DU by mid October (55% depletion). This is the steepest decline recorded at this station, and the minimum mean values were about 40 DU below those at the same time last year. The mean for September is the lowest September mean recorded at the station; 133 DU recorded at the end of the month is the lowest ever September mean daily value. Individual values of 130 DU in early October represent nearly 65% depletion and are the second lowest on record for the station. A strong spring warming episode occurred between October 20th and 28th, with a very rapid rise to 400 DU on October 22nd; this is the earliest the warming has occurred for several years and is also the steepest rise (some 250 DU in three days). Following the event mean values dropped to 180 DU (50% depletion), and then slowly rose again, reaching 230 DU by November 23rd. The final spring warming occurred between November 21st and 23rd with mean ozone values rising rapidly to around 340 DU by the end of November. The November monthly mean is the second lowest on record. Values in early December were near normal at around 360 DU, but were generally below normal throughout the late summer and autumn. Faraday preliminary mean daily total ozone (DU) Dobson No 31: constants revised 1995 April 18 1994 Aug 1 - 1995 April 30 277 270 288 301 289 297 257 247 294 233 268 264 278 275 286 306 267 267 282 254 293 306 265 304 258 205 209 216 218 242 260 310 265 233 228 196 211 241 225 220 228 211 221 160 158 151 175 161 187 188 171 192 213 181 183 159 180 189 141 138 126 123 124 141 191 268 231 195 169 146 145 134 134 141 154 156 139 129 140 148 217 360 392 354 394 375 361 334 283 209 171 154 158 157 192 155 172 187 172 173 207 204 194 212 179 196 199 206 193 198 230 213 209 269 319 284 289 309 339 345 328 344 335 347 364 352 360 358 354 361 341 355 347 349 348 350 350 332 337 336 315 318 321 331 324 317 297 279 304 323 306 309 289 299 303 285 292 299 271 255 270 285 298 311 313 298 320 305 301 295 299 309 323 308 288 294 285 299 279 303 300 284 291 295 294 292 293 272 279 286 305 289 316 314 294 317 310 289 298 285 277 274 252 237 249 256 259 279 293 293 268 293 305 302 307 278 314 324 319 306 306 304 294 296 319 334 320 307 280 262 281 294 302 283 268 287 292 279 273 274 287 270 268 268 266 266 285 283 248 281 295 290 276 281 297 299 280 268 299 291 305 301 317 328 323 335 317 271 283 228 237 229 273 Faraday monthly means and minima: 1994/95 long term mean min mean Aug 267 205 330 Sep 195 126 330 Oct 213 123 350 Nov 228 155 375 Dec 333 279 355 Jan 295 255 335 Feb 284 237 315 Mar 295 262 305 Apr 284 228 310 Preliminary ozone measurements from Halley show that mean ozone values dropped from around 180 DU at the end of August to 105 DU in early October (65% depletion), then slowly rose to reach 160 DU by November 7th. A minor peak occurred between November 7th and 17th, with a maximum of 230 DU on the 11th, followed by a decline to 185 DU. The spring warming commenced on November 24th with ozone levels peaking at around 350 DU in late November and then slowly declining. The monthly means for September and October are between those of 1992 and 1993. Mean values throughout the summer and autumn were significantly below those of the long term mean and throughout the season no daily values exceeded those of the long term mean. The data from 1956 - 1994 suggest that the mean for October 1995 will be around 120 DU, with minimum values below 100 DU. The temperature at 100 hPa rose slowly from the winter value of around -82 deg C in early October to reach -67 deg C by November 22nd (some 15 degrees below normal). The final warming then took place with the temperature reaching near normal values of around -40 deg C by the end of the month. The temperature then slowly declined, reaching -60 deg C by the end of April. Halley preliminary mean daily total ozone, (DU) Dobson No 103: constants revised 1995 April 19 (0 indicates no data.) 1994 Aug 1 - 1995 April 30 0 0 0 0 0 0 0 0 0 0 0 0 0 0 264 0 0 0 0 0 0 0 0 0 0 0 203 174 159 159 169 210 172 176 173 0 181 166 176 173 207 174 168 171 138 136 146 144 153 159 156 150 143 131 119 120 145 162 188 125 117 107 103 98 125 108 114 116 109 109 105 101 108 114 118 116 123 125 122 127 133 136 140 146 141 136 135 127 141 152 157 152 152 146 167 163 165 154 160 193 187 219 234 228 218 202 201 193 186 203 187 204 210 207 209 234 280 303 321 320 330 353 353 344 337 342 341 341 336 333 345 355 349 342 328 320 320 317 316 300 309 294 288 286 291 304 303 299 306 291 300 288 294 286 285 298 302 301 302 298 304 282 288 285 290 284 280 273 263 264 269 265 285 263 279 284 264 251 268 267 265 270 256 272 271 276 281 269 286 282 272 274 280 270 258 275 265 251 244 262 252 254 260 270 295 294 278 274 276 273 278 283 293 280 267 281 282 263 290 275 271 290 275 277 288 281 289 294 292 289 264 274 273 282 288 255 257 252 242 250 266 285 266 270 261 277 277 288 256 254 255 214 227 266 271 270 246 242 0 0 0 0 0 271 254 0 0 0 0 0 0 0 0 Halley monthly means and minima 1994/95 long term mean min mean Aug (188) 159 300 Sep 158 117 300 Oct 124 98 300 Nov 218 146 360 Dec 318 286 350 Jan 279 251 330 Feb 272 244 310 Mar 275 242 310 Apr (259) 214 300 The ozone values from Halley and Faraday are consistent with a hole of greater maximum extent than in 1993, but slightly shallower. NASA GSFC images from Meteor-3/TOMS and radiosonde data suggest that the edge of the hole was over the tip of South America and the Falkland Islands between October 11th and 21st, and was close to the region between October 29th and November 13th. The Falkland Islands now consider the ozone hole a major threat to health following cases of severe sunburn during this event. If you use or pass on this data please make acknowledgement to J D Shanklin, British Antarctic Survey. Regards, Jon Shanklin