BAS Ozone Bulletin 04/99 issued 1999 October 20
The 1999 ozone hole still covers most of Antarctica but total ozone values are now rising. The outer margins of the hole currently form a rough ellipse aligned towards the Indian Ocean. There are high ozone values over Wilkes Land. Total ozone values at Vernadsky briefly rose above 300 DU on October 7, before dropping back to 140 DU in mid October. Total ozone values at Halley are 50% below the normal for the time of year, but are slowly rising and have reached 150 DU. Stratospheric temperatures remain cold enough for stratospheric clouds to exist.
1. Data from the British Antarctic Survey (BAS) Halley station (76-deg south, 27-deg west, on the Brunt ice shelf).
Halley preliminary mean daily total ozone, (DU)
Dobson No 103: Instrument constants revised 1999 September 17.
(0 indicates no data)
1999 August 21 - 1999 October 14
231 211 206 192 205 206 218 201 209 196
185 178 173 169 167 145 140 150 175 177
151 151 199 159 136 121 125 129 125 117
114 116 139 170 162 132 130 137 140 159
142 141 140 150
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.
Stratospheric clouds, which are instrumental in the mechanism of ozone depletion, were observed from the station on July 19, August 13, 14, 15, 18 and September 1, 2, 3, 4, 10, 13, 15, 27, 28, 30.
2. Data from the British Antarctic Survey (BAS) Rothera station (68-deg south, 68-deg west on Adelaide Island).
Rothera preliminary mean daily total ozone, (DU)
(0 indicates no data or data not available)
1999 July 1 - 1999 October 19
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 0
150 175 192 207 157 274 292 280 279 239
155 151 145 136 126 110 124 124 136
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).
Vernadsky preliminary mean daily total ozone (DU).
Dobson No 31: Instrument constants revised 1999 May 10
1999 August 1 - 1999 October 17
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
195 210 176 237 156 168 154 139 141 135
141 178 203 245 161 244 304 297 264 275
191 191 182 172 158 140 141
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 and its decline. The outer margins currently form a rough ellipse aligned towards the Indian Ocean. Lowest values, below 125 DU, cover a small area close to the pole. There are high values over Wilkes Land, which is outside the polar vortex. UK Met Office charts show that 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.