BAS Ozone Bulletin 03/98 issued 1998 October 2
Total ozone values are near their minimum at Halley and Vernadsky and are broadly comparable with the past few years. The area covered by the ozone hole is larger than that seen recently.
1. Data from the British Antarctic Survey (BAS) Halley station (76-deg south, 26-deg west, on the Brunt ice shelf).
a) Ozone. Total ozone values have declined from around 260 DU in early August to 120 DU in early October at a rate of around 3 DU per day. Values are well below the long-term mean, with depletion near 60%, but comparable to the past few years. Day to day variation is around 20 DU. The preliminary mean daily value of 107 DU on September 27 is the lowest recorded for September.
Halley preliminary mean daily total ozone, (DU)
Dobson No 103: Instrument constants revised 1998 April 6.
(0 indicates no data)
1998 August 1 - 1998 September 30
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 245 216 241 179 184
174 180 192 185 192 217 224 223 197 194
157 156 164 141 149 187 198 173 146 123
127 141 145 118 118 112 107 143 138 127
b) Radiosonde data. Data from Halley show that the mean 100 hPa temperature is near or a little below normal winter values at around –81 deg C. Stratospheric clouds, which are instrumental in the mechanism of ozone depletion, were observed from the station on May 27, June 18, 19, 20, 21, 22, 23, 25, 26, 29, July 18, 23, 26, 27, 28, 29, 30, August 9, 27, 31. The displays in July showed similar features to those seen in noctilucent clouds.
Data from the British Antarctic Survey (BAS) Rothera station (68-deg south, 68-deg west on Adelaide Island).
a) Ozone. Ozone measurements from Rothera are made using a SAOZ (Systeme d'Automatique Observations Zenithales) spectrometer. This is a research instrument, but the daily ozone values are available. These show a generally similar pattern of variation to that seen at Vernadsky, though day to day variation is a little less and minimum values are a little lower. Very low values were recorded in mid September.
Rothera preliminary mean daily total ozone, (DU)
(0 indicates no data or data not available)
1998 July 1 - 1998 September 29
241 277 293 308 294 281 294 307 299 282
285 297 276 290 298 282 278 280 0 0 289
284 274 282 213 221 246 305 312 261 236
264 248 233 211 247 241 240 269 259 232
0 0 204 184 190 201 237 208 229 204 202
222 210 202 183 206 189 175 188 172 154
165 151 166 142 118 105 105 0 134 122
152 162 138 142 150 127 181 204 132
Running mean total ozone values fell from an estimated 280 DU in late July to 190 DU in late September. Values are over 40% below the long term mean, though comparable to the past few years. Day to day variation is currently around 40 DU.
Vernadsky preliminary mean daily total ozone (DU).
Dobson No 31: Instrument constants revised 1998 April 3
1998 August 1 - 1998 September 30
238 237 226 215 228 255 221 262 255 247
233 204 232 200 202 211 269 228 265 246 213
256 243 263 215 224 201 187 203 187 0
0 0 0 0 0 0 158 152 243 167
189 295 216 238 224 169 216 242 190 158
TOVS satellite images from the US NCEP/NWS/NOAA Climate Prediction Center and EP/TOMS images from the US NASA/GSFC show the development of the ozone hole. It is currently somewhat elliptical and centred away from the pole towards the Weddell Sea, with the long axis extending to the South American continent. There were low values over the base of the Antarctic Peninsula around September 17, confirming the low Rothera values. The hole covers an area of around 26 million square kilometres, which is larger than in recent years. 50 hPa temperatures are below the stratospheric cloud threshold over a large part of Antarctica, though the area covered by these temperatures is shrinking and warming has occurred over Wilkes Land. UK Met Office analyses show core 100 hPa temperatures below -86 deg C, much lower than in recent years.
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 is reduced to the Bass-Paur scale as recommended by the WMO. If you use or pass on this data please make acknowledgement to J D Shanklin, British Antarctic Survey.
Jon Shanklin