BAS ozone bulletin 13/95 issued 1995 Nov 17. Preliminary ozone values from the British Antarctic Survey Faraday station (65 south, 64 west on the coast of the Antarctic Peninsula) show that mean ozone values dropped to around 205 DU in early November before starting to rise again. Short period planetary wave activity as the edges of the ozone hole pass over the station is giving day to day variation of around 50 DU and daily values have dropped as low as 152 DU. Values are generally a little above those reached in 1993 and 1994, but below those of the long term mean. Data from our long term record for the station indicate that normal values are around 370 DU in mid November (with a range of 290 DU to 470 DU). Faraday mean ozone values dropped 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 over 300 DU in a second warming event at the end of October. Mean values dropped back again to 205 DU in early November. Longer period planetary waves are responsible for these events, with shorter period planetary wave activity giving day to day variation of around 50 DU on top of the mean value. Faraday preliminary mean daily total ozone, (DU). Dobson No 31: Constants revised 1995 November 2 1995 August 1 - November 16 300 266 270 259 284 328 302 274 238 226 232 217 212 216 275 277 279 267 218 221 229 236 223 212 200 209 204 231 217 207 222 206 202 203 242 200 195 183 185 188 151 193 271 246 219 268 227 166 205 158 141 138 214 196 173 240 202 157 154 212 261 279 369 323 316 308 317 288 303 246 169 170 168 144 133 279 283 221 184 177 230 289 263 222 280 296 217 210 266 315 353 370 377 305 215 172 157 157 152 171 235 274 317 226 195 217 186 166 Faraday provisional monthly mean total ozone (DU) Revised 1995 October 26 Aug Sep Oct 244 200 258 The mean for September is the second lowest September mean recorded at the station, the lowest being 195 DU in 1994. The minimum daily mean recorded during the month (138 DU on the 21st) is also the second lowest September minimum recorded at the station (the lowest is 126 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 ozone values are rising very slowly from the spring minimum and have reached 165 DU. These are similar to those at the same time in 1993, which has the lowest recorded November values. Day to day variation is currently around 20 DU. Data from our long term record for the station indicate that normal values are around 350 DU in mid November (with a range of 290 DU to 440 DU). Halley 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 before falling back slightly to around 135 DU. The rise then continued and had reached 165 DU by mid November. Day to day variation dropped from around 25 DU in early October to around 10 DU in late October, then increased to 20 DU in November. Stratospheric temperatures at 100 hPa, near the peak of the ozone layer, are slowly rising and are now around -75 deg C; these are substantially below normal and similar to those at the same time in 1993. Some stratospheric clouds will still be present at these temperatures. Data from our long term record for the station indicate normal values are around -57 deg C in mid November (with a range of -46 to -65 deg C). Halley preliminary mean daily total ozone, (DU) Dobson No 103: constants revised 1995 November 3 (0 indicates no data) 1995 August 1 - November 16 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 0 212 225 197 225 239 209 214 235 227 234 207 215 191 185 208 211 168 192 188 184 165 144 159 164 143 137 139 143 117 122 134 128 137 119 122 125 132 145 139 113 118 146 179 139 128 120 134 154 134 137 139 161 155 129 135 134 140 139 136 135 128 128 138 140 149 141 169 173 178 161 154 153 142 145 154 152 157 169 187 167 165 159 Halley provisional monthly mean total ozone (DU) Revised 1995 November 3 Aug Sep Oct 227 171 138 The mean for October is the equal third lowest October mean recorded at the station, the lowest being 111 DU in 1993. 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 October the hole became more elongated, but changed little in total area. The hole is now filling and became much more elongated in early November, but has since become more circular again. The centre is displaced from the south pole towards the Atlantic sector. The axis of elongation rotates 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. If you use or pass on this data please make acknowledgement to J D Shanklin, British Antarctic Survey. Note that all values are preliminary and are subject to revision from time to time. This will be the last bulletin issued from this address until mid February as I depart for Faraday station on Monday. I hope to continue issuing abbreviated reports from Faraday. Regards, Jon Shanklin