British Antarctic Survey
Ozone Bulletin 02/97 issued 1997 August 29



The ozone hole continues to form. The centre of the ozone hole has rotated clockwise around the coast of Antarctica to reach longitude 160 west. Ozone values in the Antarctic Peninsula and Weddell Sea areas have consequently risen slightly over the past fortnight, but are 15 - 25% down on the long term average. The polar vortex is centred at around 69-deg south and at this latitude receives over 8 hours sun light per day.



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


a) Ozone. Routine ozone measurements from Halley station do not start until towards the end of August because the sun is not high enough to permit measurements, however a few observations using moonlight have been made. These suggest that total ozone values fell from an estimated 300 DU in early July to around 200 DU in mid August. Low accuracy measurements on the zenith sky have now commenced and these suggest a slight rise to around 240 DU since mid-month. Ozone values are comparable to those of the past few years, but well below the long-term mean.


Halley preliminary mean daily total ozone, (DU)
Dobson No 103: Instrument constants revised 1997 May 2.
(0 indicates no data)


1997 August 1 - 1997 August 28


 

   0   0   0   0   0   0   0   0   0   0
 194   0 194 195 213 214 221 215 230 217
   0   0   0   0   0   0 221 251

Halley provisional monthly mean total ozone (DU)


Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1996/97 172 155 149 181 260 278 265 245 242 216
1995/96 219 160 129 163 253 263 248 247 224 210
1957-72 295 285 300 355 350 320 300 295 285 310

  1. Radiosonde data. Stratospheric temperatures at 100 hPa, near the peak of the ozone layer, can be used to reflect changes in ozone amount. Stratospheric clouds, which are crucial to the mechanism of ozone depletion, are likely to be present when the 100 hPa temperature is below -80 deg C and may persist whilst the temperature is below -75 deg C. Data from Halley show that the mean 100 hPa temperature for August is near the long term norm of -83 deg C, but it has risen substantially to -77 deg C over the past few days. Stratospheric clouds have been observed from the station.



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 daily ozone values are available.

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


1997 August 1 - 1997 August 25


 

   0   0   0   0   0   0   0   0   0   0
   0   0   0   0   0   0   0   0   0 259
 259 294 287 292 266

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 have been observed from the Rothera on June 8, 10, 13, 15, July 4, 17, 21, 23, and August 4.


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).


Routine ozone measurements commence at Vernadsky in early August, but some observations, of lower accuracy, are made in July. Mean total ozone values fell from an estimated 350 DU in early July to 240 DU in early August, then rose to 265 DU by mid month. Day to day variation is around 30 DU. Particularly low values were recorded on August 2nd, when the station was affected by one of the ozone reduction events associated with the forming ozone hole.


Vernadsky preliminary mean daily total ozone (DU).
Dobson No 31: Instrument constants revised 1997 August 15


1997 August 1 - 1997 August 23


 275 216 238 231 235 236 236 287 281 265
 260 262 280 290 290 259 244 240 240 253
 241 303 296

Vernadsky provisional monthly mean total ozone (DU)


Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year
1996/97 217 205 263 226 271 304 279 277 294 260
1995/96 237 194 251 228 298 285 287 278 266 258
1957-72 310 330 345 370 345 320 300 295 310 325


3 Information from other sources.


TOVS satellite images from the US NCEP/NWS/NOAA Climate Prediction Center show that intermittent ozone reduction events occurred during late July and early August. The ozone "hole" is now beginning to grow and deepen. The centre of the hole is located near the edge of the continent, in sun-lit latitudes, and is rotating around it with a period of about a month. It is currently centred near 65-deg south, 160-deg west, which is rather further north than usual. The normal circumpolar high ozone belt is present. UK Met Office analyses show that the main centre of the polar vortex at around 70-deg south, 150-deg west, with a secondary centre at around 82-deg south, 70-deg east.



Further information is available on the BAS ozone web page, which contains earlier bulletins, data 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. 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.