• Abstract
• References

FIGURES

• Figure 1
• Figure 2
• Figure 3
• Figure 4
• Figure 5
• Figure 6
• Figure 7
• Figure 8
• Figure 9

The studies on the developments of the Antarctic ozone hole, since the discovery by Farman-Gardiner and Shanklin, Farman et al., are been intense efforts to monitoring the abundance, spatial and temporal evolutions.

The concentration of stratospheric ozone can be sampled in situ by measurements with balloon sounding or aerial platform as APE-GAIA Project, Carli et al. or by remote sensing techniques by ground based stations or satellite monitors. Because the meteo conditions and logistic high costs, the balloon data not always are available in the time and place required. The flights of a stratospheric aircraft, of course, multiply the costs and the logistic problems. The orbital parameters of satellites and their pixel dimensions don’t allow to follow fast fluctuations, De Petris et al.. or local phenomena but are very useful for climatological studies.

The studies of the ozone hole needs, instead, a large amount of data in time or space; then only a ground-based network solves these problems. Of course in situ measurements are fundamental to study the local situation due photo-chemical reactions, but they need reference data sampled at ground.

The Italian National Antarctic Program (P.N.R.A.) since 1992 installed a spectrophotometer Brewer in Belgrano II, the Antarctica Argentinean base at 77.87° S - 34.62° W. This equipment, managed by Direccion Nacional del Antartide of Buenos Aires (D.N.A.), is involved in the WMO ozone hole forecast program too, Anav et al.. Moreover, to study the rising of the hole over the northern latitudes, since 1994 a second Brewer is installed in Ushuaia, Prov. di Tierra del Fuego, 54.82° S ? 68.32° W, Di Menno et al..

In the paper the deepening over the Belgrano of the ozone hole during last 5 years as seasonal value computed by direct sun sampling (DS), fig. 1, shows a depletion in the 2000 respect of 1995 of 33.1% and 6.5% for early springtime and summer respectively.

Instead, over Ushuaia the spring path of the daily mean values, in the years 1994 - 1999, fig. 2, don’t shows a similar trend because only cyclically the ozone hole rises the South America, with period of 20 days about. The flickering during the springtime is been between 270.1 D.U. and 318.4 D.U. for DS, and 273.7 D.U. and D.U. 313.0 for ZS.

The slope of linear regression of DS vs. TOMS is 0.966, with a linear correlation coefficient r = 0.47, fig. 3. The slope value is close to 1 as theoretical results but, the low r is due to several factors: the grid dimension, about 1° • 1.25° degree, the time of the satellite over-passing, the horizontal gradient of the total ozone in the area, the use of the daily mean values of the Brewer sampling.

Similar results are for Belgrano; where the data set is shorter for weather conditions, fig. 4. The linear regression parameters of DS vs. TOMS are: 0.90 as slope with an r = 0.32 because Belgrano in the period was always into the ozone hole with values quite constant.

The Brewer spectrophotometer allows, by a particular routine named Focused Sun (FZ) to improve the DS total ozone measure when the sun is very low over the horizon, like in Antarctica, during all the springtime and autumn. The permanence into the ozone hole is confirmed by the constant path of samples, fig. 5, plotted versus Solar Zenith Angle (SZA). Inside the hole also the SO₂ contribute to ozone total content, sampled to evaluate the ozone correctly, Kerr et al., and plotted versus air mass is constant, fig. 6.

The Umkehr routine implemented in the Brewer give the vertical profile of ozone between 2 to 50 Km; during the APE-GAIA Campaign several profiles was obtained.

The severe weather over Belgrano conditions the Umkehr sampling and only a profile during the campaign is valid; the Umkehr profile shows some gaps but the height of the two relative maxims, about 22.2 Km and 12 Km, is in good agreement with the ozone-sounding performed by INTO of Spain, fig. 7. Of course the quantitative ozone values aren’t useful for a comparison. The total ozone content as DS sampled with Brewer, 114.5 D.U., is in agreement with the sounding, 106 D.U..

On the contrary in Ushuaia several profiles, 28 during the APE-GAIA Campaign, are been sampled, fig. 8. In the profiles it is clear the depletion of the ozone linked with ozone hole rotation over South America, fig. 9.

Concluding, the stratospheric ozone sampled in Belgrano and Ushuaia are in good agreement with some reference as TOMS or ozone-sounding data. The paths confirm the different behaviour of the two sites; the first inside the hole during the spring time, the second one only periodically. In fact it is possible detect the effects of the rotation of the ozone hole that arrive over Ushuaia. This information is important also for the consequences over the local population when communication media diffuses the ozone bulletins.

Of course the whether conditions play a very important role over the sampling possibility and, this will be a field of studies for the authors.

The authors are grateful to P.N.R.A. Program and APE-GAIA Project for funding the research.

A particular thanks is directed to the D.N.A.-I.A.A. staff in Buenos Aires and to operators in Belgrano II that, during these years, have managed the Brewer in very severe logistic and climatic conditions.

The authors are grateful to dr. G. Labow of the NASA/GSFC TOMS Team staff for the help during the APE-GAIA Campaign, and to INTA of Spain for the sounding data in Belgrano.

References

Anav A., L. Ciattaglia, M. Di Menno, M. Moriconi, C. Rafanelli ? 1998 - Five years of total Ozone measurements at Belgrano2 Antarctic station - Fifth WMO Meeting on Brewer operation, calibration and data reporting. - Halkidiki, Greece, Sep. 16-18.

Carli B., Cortesi U., C.E. Blom, M. P. Chipperfield, G. De Rossi, G. Redaelli ? 2000 ? Airborne Polar Experiment, Geophysica Aircraft in Antarctica (APE-GAIA) ? SPARC Newsletter n° 15, July, pp. 21-24.

De Petris M., M. Gervasi, G. Moreno, M. Parisi, M. Storini ? 1993 ? Solar-induced effects on the high-latitude atmospheric O₃ content. ? Trends in Geophys. Res., 2, pp 459-465.

Di Menno I., C. Rafanelli, R. Iturraspe, D. Turne, G. Magnifico ? 1996 - Misure radiometriche in ambiente periantartico: Caratteristiche del sito di Ushuaia - IFA R.I. 96/17 December.

Farman J. C., B. G. Gardiner, J. D. Shanklin ? 1985 ? Large losses of total ozone in Antarctica reveal seasonal ClO_x/NO_x interaction - Nature, 315, p. 207.

Kerr J. B., C. T. McElroy, W. J. F. Evans ? 1983 ? The automated Brewer Spectrophotometer for measurements of SO2, O3 and aerosols ? Meteorological Observations and Instrumentation, WMO/A. Metereol. Soc./CMOS, Toronto, Canada, pp 470-472.