BAS ozone bulletin 10/95 issued 1995 Oct 30. Preliminary ozone values from the British Antarctic Survey Faraday station (65 south, 64 west on the coast of the Antarctic Peninsula) show mean ozone values dropping from values of around 290 Dobson Units (DU) at the beginning of August to around 180 DU at the end of September (45% depletion). The first week of October saw a major spring warming event, with a rise in mean total ozone to over 300 DU as the circumpolar high ozone belt moved across the station. Mean values then fell back to around 200 DU in mid October before rising again to around 260 DU at present. Planetary wave activity as the edge of the ozone hole passes over the station is giving day to day variation of around 50 DU. Values are generally above those reached in 1993 and 1994, but well below those of the long term mean. Data from our long term record for the station indicate normal values are around 360 DU in late October (with a range of 290 DU to 480 DU). Faraday preliminary mean daily total ozone, (DU). Revised 1995 October 26 1995 August 1 - October 26 300 266 270 259 284 328 302 274 238 226 232 217 212 216 275 277 279 267 218 221 229 236 224 212 200 209 204 231 217 207 222 206 202 203 242 200 195 183 185 188 151 193 271 246 219 268 227 166 205 158 141 138 214 196 173 240 202 157 154 212 261 279 369 323 316 308 317 288 303 246 169 170 169 144 133 280 283 222 184 177 231 289 263 222 280 296 218 Faraday provisional monthly mean total ozone (DU) Revised 1995 October 26 Aug Sep 244 200 The mean for September is the second lowest September mean recorded at the station, the lowest being 195 DU in 1994. Preliminary ozone measurements from the British Antarctic Survey Halley station (76 south, 26 west on the Brunt ice shelf) show that mean total ozone values dropped slowly from around 250 DU at the beginning of August to around 220 DU in early September and then fell rapidly to a minimum of 125 DU at the end of September (60% depletion). The decline then halted and ozone values rose very slowly to around 140 DU in mid October. Mean values are now steady at around 135 DU, similar to those at the same time in 1993/94 and below those at the same time last year. Day to day variation has dropped from around 25 DU in early October to around 10 DU. Data from our long term record for the station indicate normal values are around 305 DU in late October (with a range of 270 DU to 360 DU). Stratospheric temperatures at 100 hPa, near the peak of the ozone layer, are steady at around -79 deg C; this is substantially below normal and similar to those at the same time in 1993/94, but well below those at the same time last year. Some stratospheric clouds will still be present at this temperature. Data from our long term record for the station indicate normal values are around -67 deg C in late October (with a range of -60 to -73 deg C). Halley preliminary mean daily total ozone, (DU) (0 indicates no data) 1995 August 1 - October 29 Revised 1995 October 30 0 0 0 0 0 0 0 221 228 231 248 244 0 0 0 0 0 0 0 0 0 0 0 0 0 0 212 225 197 225 239 209 214 235 227 234 205 213 189 183 206 210 167 192 187 183 164 143 159 163 142 136 137 141 116 121 133 126 135 117 120 123 131 143 137 112 117 145 177 138 126 118 132 152 132 134 137 159 152 128 133 132 138 138 134 134 125 125 137 139 Halley provisional monthly mean total ozone (DU) Revised 1995 October 30 Aug Sep 227 170 TOVS satellite images from the US NCEP/NWS/NOAA Climate Prediction Center show that ozone depletion intensified during September, with the ozone "hole" covering most of the Antarctic continent and centred close to the south pole. Ozone values at Halley and Faraday were a little above those of last year, because the centre of the hole was further away from the BAS stations than in 1994. During the first half of October the hole became more elongated; the axis of elongation is currently aligned towards the South Atlantic. The axis of elongation is rotating around the Antarctic continent with a period of about a month. This rotation of the "hole" gives rise to the larger day to day variation in ozone amount seen at Faraday, which is sometimes inside and sometimes outside the ozone hole. The edge of the hole clipped the tip of South America and the Falkland Islands between October 12 and 14. The hole is beginning to fill and has become more elongated; however the small decline in values at Halley suggests that ozone depletion is still taking place. If you use or pass on this data please make acknowledgement to J D Shanklin, British Antarctic Survey. Regards, Jon Shanklin If you have difficulty replying to the originating e-mail adress try j.shanklin @ bas.ac.uk or jds @ mail.ast.cam.ac.uk