British Antarctic Survey Ozone Bulletin 17/95 issued 1996 June 11.

This bulletin presents total column ozone measurements made using a Dobson ozone spectrophotometer. Note that all ozone values are preliminary and are subject to revision from time to time when the instrument constants are re-evaluated. All ozone data is reduced to the Bass-Paur scale as recommended by the WMO. I was away in the Antarctic from mid November until mid February.

1. Data from Faraday (Vernadsky) station (65 south, 64 west on the coast of the Antarctic Peninsula).

Faraday station was run by the British Antarctic Survey until 1996 February 6, when it was handed over to the Ukrainian Antarctic Research Centre and became Vernadsky station. Ozone measurements from 1996 January 1 until the handover date were made by Ukrainian scientists under my supervision.

Preliminary mean daily ozone values dropped from values of around 280 Dobson Units (DU) at the beginning of August to around 175 DU at the end of September (50% depletion). Individual daily values dropped as low as 132 DU. 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 190 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 200 DU in early November before slowly rising to around 315 DU in the final warming event of the year in mid December. Longer period planetary waves were 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. Values slowly declined from the December peak to around 260 DU at the end of April.

Generally values in the 95/96 season were a little above those reached in 1993 and 1994 during the first half of the season and below during the second half. The final spring warming was much later than in either year. Values were significantly below those of the long term mean throughout the season.

Faraday preliminary mean daily total ozone (DU). Dobson No 31: Constants revised 1995 December 14

1995 August 1 - 1996 April 30

294 260 264 253 277 322 296 267 231 219 226 210 205 209 268 270 272 261 211 216 223 229 218 205 193 202 197 224 210 201 215 199 195 196 236 193 188 176 179 181 150 187 264 239 212 261 220 159 199 152 135 132 208 190 167 234 196 151 148 206 254 273 363 317 310 302 311 281 296 240 163 164 162 138 127 273 276 216 178 170 223 283 256 216 273 290 211 204 260 309 347 364 371 298 209 166 151 151 146 165 229 267 311 220 188 210 180 160 174 180 205 269 297 295 319 288 256 177 222 254 256 232 253 279 253 242 252 236 296 306 296 329 314 336 332 330 321 294 288 309 323 311 290 293 291 301 320 325 322 332 296 290 287 300 308 287 282 303 294 293 296 290 287 287 285 278 271 260 272 291 296 273 299 299 288 294 285 282 302 287 275 264 260 246 258 276 302 297 264 278 263 275 286 296 261 256 266 271 297 282 302 288 312 315 291 295 303 305 309 295 282 301 293 282 273 281 311 295 291 289 253 278 304 307 303 285 259 249 228 250 272 292 303 315 279 267 258 261 292 264 281 266 249 241 282 279 274 312 282 266 274 282 264 275 267 276 259 268 304 251 253 249 257 253 253 232 246 270 259 261 259 283 236 219

Faraday provisional monthly mean total ozone (DU)

	Period    Aug  Sep  Oct  Nov  Dec  Jan  Feb  Mar  Apr  Year
	1995/6    237  194  251  228  298  285  287  278  266  258
	1957-72   310  330  345  370  345  320  300  295  310  325

Many of the monthly means are either the lowest or near the lowest on record. The yearly mean is the lowest on record.

2. Data from Halley station (76 south, 26 west, on the Brunt ice shelf) run by the British Antarctic Survey.

Preliminary mean daily ozone values dropped slowly from around 240 DU at the beginning of August to around 200 DU in early September, but fell rapidly to a minimum of 120 DU at the end of September (60% depletion). The decline then halted and ozone values rose slowly, reaching around 200 DU in early December. Finally, a more rapid spring warming took place, reaching a maximum of just over 300 DU in mid December. Values slowly declined from this peak, reaching 215 DU in mid April. Day to day variation was small, averaging around 20 DU.

The early part of the season was similar to 1993, however the final spring warming was later and reached a lower peak. Values after the peak were lower than in 1993. Throughout the season the running mean daily values were never higher than the reference period extreme minimum.

Halley preliminary mean daily total ozone, (DU) Dobson No 103: constants revised 1996 March 8 (0 indicates no data)

1995 August 1 - 1996 April 30

0 0 0 0 0 0 0 211 218 222 239 235 0 0 0 0 0 0 0 0 0 0 0 0 0 0 210 218 194 215 225 199 200 216 208 214 191 199 175 170 192 199 159 183 176 174 156 138 151 156 135 128 128 131 109 114 125 118 125 109 113 115 123 135 129 105 109 137 167 131 118 112 125 143 124 129 130 152 146 121 126 126 132 131 127 127 121 121 130 132 141 133 160 164 168 152 146 145 136 138 147 145 150 162 180 163 159 152 153 152 149 151 160 165 160 173 179 188 197 192 220 196 187 181 174 177 189 197 213 206 222 228 255 253 250 295 249 246 264 268 294 311 318 303 304 294 290 289 284 288 278 264 281 286 289 285 272 268 271 271 257 263 271 267 277 275 275 260 256 245 250 259 254 256 263 261 258 256 256 238 0 237 247 252 251 249 269 259 248 259 248 232 229 239 247 249 264 246 244 238 249 244 241 218 254 252 224 236 241 263 261 277 270 267 253 242 252 237 225 244 240 264 229 241 256 250 272 250 257 246 245 232 234 246 249 239 255 260 260 252 236 235 217 231 243 235 216 231 235 218 228 229 235 207 203 223 215 219 223 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Halley provisional monthly mean total ozone (DU)

	Period    Aug  Sep  Oct  Nov  Dec  Jan  Feb  Mar  Apr  Year
	1995/96   219  160  129  163  253  263  248  247  224  210
	1957-72   295  285  300  355  350  320  300  295  285  310

Many of the monthly means are either the lowest or near the lowest on record. All the monthly means from January onwards and the yearly mean are the lowest on record.

Stratospheric temperatures at 100 hPa, near the peak of the ozone layer can be used to reflect changes in ozone amount. Stratospheric clouds, which are crucial to the mechanism of ozone depletion, are likely to be present when the 100 hPa temperature is below -80 deg C and may persist whilst the temperature is below -75 deg C. In the 1995/96 season the 100 hPa temperature remained at winter values (below -80 deg C), until early October. It then rose slowly, reaching -75 deg C in mid November, before rising more rapidly to peak at -40 deg C in late December. During the late summer and autumn slow cooling took place, with the temperature reaching -60 deg C by the end of April. Almost throughout the season the lower stratospheric temperature was below the long term mean. The departure is particularly marked from mid October to mid December and from mid January to mid February. The season until mid November was similar to 1993, but the spring warming was later in 1995.

3 Information from other sources; August - November 1995.

TOVS satellite images from the US NCEP/NWS/NOAA Climate Prediction Center showed 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 started to fill and became much more elongated in early November, but become more circular again later in the month. The axis of elongation rotated around the Antarctic continent with a period of about a month. This rotation of the "hole" gave rise to the larger day to day variation in ozone amount seen at Faraday, which was 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.

Regards, Jon Shanklin


Created at Tue Jun 11 15:44:02 GMT 1996 by asc2html.pl and WMC from text by JDS.