BAS Ozone Bulletin 04/98 issued 1998 October 15


Total ozone values are past their minimum at Halley and Vernadsky and are broadly comparable with the past few years with a maximum depletion of around 60%. The area covered by the ozone hole has been larger than that seen in recent years.


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 declined from around 260 DU in early August to 120 DU in early October at a rate of around 3 DU per day and have since risen to around 125 DU. 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 10 DU.


Halley preliminary mean daily total ozone, (DU)
Dobson No 103: Instrument constants revised 1998 October 15.
(0 indicates no data)


1998 August 1 - 1998 October 14

 0 0 228 222 223 0 0 0 0 217

0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 245 216 241 179 184

174 180 192 185 193 220 227 226 200 199

162 161 169 145 151 192 203 178 148 125

129 146 150 120 123 114 108 148 140 128

124 117 129 112 115 115 114 123 130 134

131 125 123 120


Halley provisional monthly mean total ozone (DU)


Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1998/99 217 165
1997/98 218 171 141 210 286 267 262 264 261 231
1996/97 173 155 148 181 260 278 265 247 243 217
1995/96 218 160 130 164 252 261 249 246 226 212
1957-72 295 285 300 355 350 320 300 295 285 310

Note that August and April do not have observations on every day, and that the routine measurement season is now longer than it was in 1957 - 72. Measurements made at the start of the season are of lower accuracy than in mid summer due to the low solar elevation or use of moonlight. Gif images showing the data are available on the BAS ozone web-page.

b) Radiosonde data. Data from Halley show that the mean 100 hPa temperature is still at around –81 deg C, some 7 deg C below normal for the time of year. 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 and do not show such pronounced wave activity. 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 October 11


 277 284 301 288 300 303 0 0 286 284

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

152 162 138 142 150 127 181 204 128 115

107 115 131 146 140 162 182 152 123 126

121


Note: The instrument calibration is in error by around 15% at 100 DU, reading too low.


b) Stratospheric clouds. Nacreous or mother-of-pearl clouds are regularly seen from stations along the Antarctic Peninsula between early May and October, with a peak in July. There is some evidence that their frequency of occurrence has increased since the mid 1950s. This year they were observed from Rothera on June 13, 30, July 2, 3, 4, 8, August 15, September 16, 17, 18.


3. Data from the Ukrainian Antarctic Research Centre Vernadsky station (65-deg south, 64-deg west on the coast of the Antarctic Peninsula, formerly the BAS Faraday station).


Running mean total ozone values fell from an estimated 280 DU in late July to 190 DU in early September. Strong long period wave activity with a period of about a month is giving a variation of around 25 DU on this value and day to day variation is currently around 40 DU. Values are about 55% below the long term mean, though comparable to the past few years.


Vernadsky preliminary mean daily total ozone (DU).
Dobson No 31: Instrument constants revised 1998 October 12


1998 August 1 - 1998 October 14


 275 269 284 252 223 255 288 296 270 237

233 232 224 210 223 250 218 257 250 242

229 199 227 195 198 206 264 223 260 241 208

251 238 258 210 219 196 182 198 184 185

195 181 199 181 145 131 153 147 240 164

186 292 213 234 220 166 213 239 187 155

138 157 148 177 179 196 248 258 160 162

151 177 207 245


Vernadsky provisional monthly mean total ozone (DU)


Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1998/99 240 199
1997/98 261 251 235 240 297 281 266 280 281 266
1996/97 208 203 265 225 272 307 281 277 283 258
1995/96 240 199 252 230 296 284 285 276 264 258
1957-72 310 330 345 370 345 320 300 295 310 325

b) Radiosonde flights at Bellingshausen, Marambio and Rothera show 100 hPa temperatures that are a little below the seasonal normal. Anomalously low 100 hPa temperatures were recorded at Marambio on September 18. Stratospheric clouds were seen from Vernadsky on June 13 and July 14


4. Information from other sources.


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 towards the Atlantic Ocean. There were low values over the base of the Antarctic Peninsula around September 17, confirming the low Rothera values. The edge of the ozone hole crossed over the tip of South America around September 7, 18, October 1 and 11. The hole covers an area of around 26 million square kilometres, which is larger than in recent years. The 50 and 100 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 -88 deg C, much lower than in recent years, however radiosonde data from the South Pole give values some 6 deg C warmer than the analyses.



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