BAS Ozone Bulletin 03/99 issued 1999 October 4


The 1999 ozone hole covers virtually all of Antarctica with total ozone values still declining at around 2.5 DU per day. The outer margins of the hole currently form a rough heart shape with the axis of the heart aligned towards South America. Lowest values cover a broad area offset a little from the pole towards the Atlantic Ocean. Total ozone values at Vernadsky dropped below 140 DU in late September, nearly 60% below the normal for the time of year. Total ozone values at Halley have dropped below 130 DU, over 55% below the normal for the time of year. Ozone values as measured at Rothera are below 120 DU.


1. Data from the British Antarctic Survey (BAS) Halley station (76-deg south, 27-deg west, on the Brunt ice shelf).

 

  1. Ozone. Total ozone values at Halley are declining at around 2.6 DU per day. Mean total ozone values fell from around 220 DU in late August to around 150 DU in mid September, then rose briefly to reach 200 DU on September 23rd when planetary wave activity brought the edge of the ozone hole close to the station. This is the highest ozone amount at the station in the last 10 days of September since 1990. The fall continued, and values dropped below 130 DU at the end of the month; this is over 55% below the normal for the time of year.


Halley preliminary mean daily total ozone, (DU)
Dobson No 103: Instrument constants revised 1999 September 17.
(0 indicates no data)


1999 August 21 - 1999 September 29
0 0 0 0 0 175 180 254 220 181 220

231 211 206 192 205 206 218 201 209 196

185 178 173 169 167 145 140 150 175 177

151 151 199 159 136 126 126 131 127


Halley provisional monthly mean total ozone (DU)


Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1999/00 205
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 is near -80 deg C and is close to the normal for the time of year.


Stratospheric clouds, which are instrumental in the mechanism of ozone depletion, were observed from the station on July 19 and August 13, 14, 15, 18.



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 research instrument has a preliminary calibration such that it reads about 15% low compared to Dobson measurements at 100 DU, and is in agreement at 300 DU. The mean daily total ozone values show a generally similar pattern of variation to that seen at Vernadsky, though day to day variation does not show such pronounced wave activity and minimum values are a little lower. Mean total ozone values have dropped from 290 DU at the beginning of August to 115 DU in late September, a rate of decline of 2.9 DU per day.

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


    1999 July 1 - 1999 September 29


    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

    225 222 219 224 241 214 210 210 225 219 223

    186 175 0 165 164 194 183 162 158 164

    154 143 162 160 184 149 148 163 162 162

    159 173 161 166 130 129 119 116 114


    Rothera provisional monthly mean total ozone (DU)


    Period Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
    1999/00 274 243
    1998/99 288 239 159 166 252 264 270 279 267 277 300 287
    1997/98 270 280 267 263

  3. 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 140 DU in late September (60% depletion), giving a rate of decline of around 2.5 DU per day. There is weak long-period wave activity present, with a period of about a month.

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


    1999 August 1 - 1999 September 29


    291 314 270 270 277 283 257 248 249 260

    224 210 225 263 253 259 214 229 227 221

    221 239 221 231 235 202 211 226 256 231 249

    214 187 174 181 169 232 220 191 167 178

    196 191 169 178 228 194 168 218 203 177

    195 210 176 237 156 168 154 139 141


    Vernadsky provisional monthly mean total ozone (DU)


    Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
    1999/00 244
    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

  3. Radiosonde data. Radiosonde flights at Marambio and Rothera show that the 100 hPa temperature is generally remaining below -75°C.; this is a few degrees below the normal for the time of year, but within the historic range of variation.



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. The outer margins currently form a rough heart shape with the axis of the heart aligned towards South America. Lowest values, below 125 DU, cover a broad area offset a little from the pole towards the Atlantic Ocean. UK Met Office 100 hPa forecast charts suggest that the vortex edge will swing towards the tip of South America over the next 48 hours. The 100 hPa temperature remains below -75 deg C over much 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 are reduced to the Bass-Paur scale as recommended by the WMO. The reference period used for the normals is 1957 - 1972. If you use or pass on data in this bulletin please make acknowledgement to J D Shanklin, British Antarctic Survey.

 

Jon Shanklin