BAS Ozone Bulletin 01/99 issued 1999 September 6


The 1999 ozone hole is forming and now covers all of Antarctica with minimum ozone values decreasing steadily. Lowest values are currently over the Antarctic Peninsula and West Antarctica. Total ozone values at Vernadsky have dropped below 175 DU, 45% below normal for the time of year. Ozone observations have just begun at Halley and measurements give values around 25% lower than average for the time of year.


1. Data from the British Antarctic Survey (BAS) Halley station (76-deg south, 26-deg west, on the Brunt ice shelf).

 

  1. Ozone. Ozone measurements have only just begun at Halley and are of low accuracy. Mean total ozone values are around 200 DU, 24% below average for the time of year.


Halley preliminary mean daily total ozone, (DU)
Dobson No 103: Instrument constants revised 1998 November 13.
(0 indicates no data)


1999 August 21 - 1999 September 2

 0 0 0 0 0 175 180 254 220 175 220

231 213


Halley provisional monthly mean total ozone (DU)


Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1999/00 204 …
1998/99 221 162 140 183 255 272 259 254 267 224
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.

  1. Radiosonde data. Data from Halley show that the mean 100 hPa temperature remains below -80 deg C and is close to normal.

    Stratospheric clouds, which are instrumental in the mechanism of ozone depletion, were observed from the station on July 19.



2. Data from the British Antarctic Survey (BAS) Rothera station (68-deg south, 68-deg west on Adelaide Island).

 

  1. 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.


    2. Rothera preliminary mean daily total ozone, (DU)
    (0 indicates no data or data not available)


    1999 July 1 - 1999 August 31


     270 277 293 278 293 324 304 294 301 311

    298 294 294 293 298 273 247 219 0 211

    231 276 279 277 243 224 238 244 265 273 283

    299 313 281 270 267 290 0 258 260 260

    210 228 239 256 249 243 200 232 262 239

    225 222 219 224 241 214 210 210 225 219 235


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

     

  2. 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 6, 7, 9, 10, 12, 29, July 12, 13, August 22 and 31.

 

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).

 

  1. Ozone. Running mean total ozone values fell from around 290 DU in late July (10% depletion) to 170 DU in early September (45% depletion).


    2. Vernadsky preliminary mean daily total ozone (DU).
    Dobson No 31: Instrument constants revised 1999 May 10


    1999 August 1 - 1999 September 5


    291 314 270 270 277 283 257 0 249 260

    224 210 225 263 253 259 214 229 0 0

    0 239 221 231 235 202 211 226 256 231 249

    214 187 174 181 169


    Vernadsky provisional monthly mean total ozone (DU)


    Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
    1998/99 241 200 218 305 278 288 289 273 279 263
    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

  2. Radiosonde data. Radiosonde flights at Marambio and Rothera show that the 100 hPa temperature is generally below -75°C, a little lower than normal for the time of year.



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 progressive development of the ozone hole. Lowest values are currently over West Antarctica and the Antarctic Peninsula, with depletion affecting all of Antarctica.



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