Balloonborne ozone and aerosol measurements in the antarctic ozone ...
Balloonborne ozone and aerosol measurements in the antarctic ozone hole
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D.J. HOFMANN, J.W. HARDER, S.R. ROLE, and J.M. ROSEN Department of Physics and Astronomy University of Wyoming Laramie, Wyoming 82071
Springtime ozone in the south polar vortex region has been on the decline since about 1975 (Farman, Gardiner, and Shanklin 1985; Stolarski et al. 1986). This phenomenon has come to be known as the "antarctic ozone hole" and has important implications for stratospheric chemistry and climate studies. The source of this ozone depletion is presently unknown but may be related to chlorine chemistry on polar stratospheric cloud particles (Solomon et al. 1986; McElroy et al. 1986). Because the latter is related to anthropogenic releases of chlorofluorocarbons, a great deal of interest has arisen concerning this phenomenon. For this reason the National Ozone Expedition (NozE) was mounted in 1986 using winter fly-in flights to McMurdo Station in August, which is approximately the time the ozone reduction begins. The University of Wyoming Atmospheric Physics group participated in this expedition through balloonborne measurements of the vertical distribu tion of ozone and aerosol particles. Between 24 August and 6 November, 33 ozone soundings, 6 aerosol soundings, and 3 condensation nuclei soundings were conducted using polyethylene balloons which were able to penetrate the cold (< - 80°C) antarctic stratosphere. Results of the ozone measurements were reported in Nature (Hofmann et al. 1987), and results of the aerosol measurements have been submitted to the Journal of Geophysical Research. We summarize these results here. The figure shows the ozone partial pressure profiles in late August, shortly after our arrival at McMurdo Station when ozone levels were near normal and at the height of the depletion in mid-October when the smallest ozone column was observed. We find that although total ozone is reduced only about 50 percent, the loss in the 12-20-kilometer region is at least 75 percent. The limited region of the depletion and large magnitude were unexpected results and are important observations for defining the depletion mechanism. The aerosol measurements were important in two ways. First, the stratospheric sulfate aerosol layer, which is due to volcanic eruptions around the globe, was found to remain constant in height and magnitude during the time that the ozone was decreasing. This suggests that dynamic phenomena such as upwelling, which would alter the aerosol distribution, are not important in the ozone depletion process. Second, although balloon flights were made on four occasions when the stratosphere was cold enough for polar stratospheric clouds to form and were actually observed visually on two occasions, no unusual particles were registered in the optical particle counters employed. This suggests that the concentration of the cloud particles is probably too low (less than about 0.001 per cubic centimeter) to be observed in the counters employed. This would be consistent with the clouds being similar to high-
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580 1868 I
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OZONE PARTIAL PRESSURE (nh) Ozone profiles obtained at McMurdo Station before (August) and after (October) the spring decline of ozone took place in 1986. ("mb" denotes "millibars." "rib" denotes "nanobars." "km" denotes "kilometers.")
altitude cirrus, i.e., large particles (5-50 micrometers) of low concentration composed predominantly of water ice. The ozone measurements will be repeated during winter flyin 1987 and additional particle counter flights are planned in hope of further defining the temporal and spatial variations of ozone and to attempt again to detect polar stratospheric cloud particles. D.J. Hofmann and J.W. Harder were at McMurdo from 22 August to 15 November, S. R. Rolf from 22 August to 10 October, and N.T. Kjome and G.L. Olson from 7 October to 15 November. This work was supported in part by National Science Foundation grant DPP 85-15472 and by the National Aeronautics and Space Administration grant NAG W-918. References
Farman, J.C., B.C. Gardiner, and J.D. Shanklin. 1985. Large losses of total ozone in Antarctica reveal seasonal CLO,/NO interaction. Nature, 315, 207-210. Hofmann, D.J., J.W. Harder, S.R. Rolf, and J.M. Rosen. 1987. Balloonborne observations of the development and vertical structure of the Antarctic ozone hole in 1986. Nature, 326, 59-62. McElroy, M.B., R.J. Salawitch, S.C. Wofsy, and J.A. Logan. 1986. Reductions of Antarctic ozone due to synergistic interactions of chlorine and bromine. Nature, 321, 759-762. Solomon, S., R.R. Garcia, F.S. Rowland, and D.J. Wuebbles. 1986. On the depletion of Antarctic ozone. Nature, 321, 755-758. Stolarski, R.S., A.J. Krueger, M.R. Schoeber!, R.D. Peters, P.A. Newman, and J.C. Alpert. 1986. Nimbus 7 SB(JVITOMS measurements of the springtime Antarctic ozone hole. Nature, 322, 808-811.
AN1ARCTIC JOURNAL
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16
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D.J. HOFMANN, J.W. HARDER, S.R. ROLE, and J.M. ROSEN Department of Physics and Astronomy University of Wyoming Laramie, Wyoming 82071
Springtime ozone in the south polar vortex region has been on the decline since about 1975 (Farman, Gardiner, and Shanklin 1985; Stolarski et al. 1986). This phenomenon has come to be known as the "antarctic ozone hole" and has important implications for stratospheric chemistry and climate studies. The source of this ozone depletion is presently unknown but may be related to chlorine chemistry on polar stratospheric cloud particles (Solomon et al. 1986; McElroy et al. 1986). Because the latter is related to anthropogenic releases of chlorofluorocarbons, a great deal of interest has arisen concerning this phenomenon. For this reason the National Ozone Expedition (NozE) was mounted in 1986 using winter fly-in flights to McMurdo Station in August, which is approximately the time the ozone reduction begins. The University of Wyoming Atmospheric Physics group participated in this expedition through balloonborne measurements of the vertical distribu tion of ozone and aerosol particles. Between 24 August and 6 November, 33 ozone soundings, 6 aerosol soundings, and 3 condensation nuclei soundings were conducted using polyethylene balloons which were able to penetrate the cold (< - 80°C) antarctic stratosphere. Results of the ozone measurements were reported in Nature (Hofmann et al. 1987), and results of the aerosol measurements have been submitted to the Journal of Geophysical Research. We summarize these results here. The figure shows the ozone partial pressure profiles in late August, shortly after our arrival at McMurdo Station when ozone levels were near normal and at the height of the depletion in mid-October when the smallest ozone column was observed. We find that although total ozone is reduced only about 50 percent, the loss in the 12-20-kilometer region is at least 75 percent. The limited region of the depletion and large magnitude were unexpected results and are important observations for defining the depletion mechanism. The aerosol measurements were important in two ways. First, the stratospheric sulfate aerosol layer, which is due to volcanic eruptions around the globe, was found to remain constant in height and magnitude during the time that the ozone was decreasing. This suggests that dynamic phenomena such as upwelling, which would alter the aerosol distribution, are not important in the ozone depletion process. Second, although balloon flights were made on four occasions when the stratosphere was cold enough for polar stratospheric clouds to form and were actually observed visually on two occasions, no unusual particles were registered in the optical particle counters employed. This suggests that the concentration of the cloud particles is probably too low (less than about 0.001 per cubic centimeter) to be observed in the counters employed. This would be consistent with the clouds being similar to high-
246
A L 20 T
P R E S 50
S Ii R ioo E (Nb)
T U D E ()
280
10
580 1868 I
108
260
OZONE PARTIAL PRESSURE (nh) Ozone profiles obtained at McMurdo Station before (August) and after (October) the spring decline of ozone took place in 1986. ("mb" denotes "millibars." "rib" denotes "nanobars." "km" denotes "kilometers.")
altitude cirrus, i.e., large particles (5-50 micrometers) of low concentration composed predominantly of water ice. The ozone measurements will be repeated during winter flyin 1987 and additional particle counter flights are planned in hope of further defining the temporal and spatial variations of ozone and to attempt again to detect polar stratospheric cloud particles. D.J. Hofmann and J.W. Harder were at McMurdo from 22 August to 15 November, S. R. Rolf from 22 August to 10 October, and N.T. Kjome and G.L. Olson from 7 October to 15 November. This work was supported in part by National Science Foundation grant DPP 85-15472 and by the National Aeronautics and Space Administration grant NAG W-918. References
Farman, J.C., B.C. Gardiner, and J.D. Shanklin. 1985. Large losses of total ozone in Antarctica reveal seasonal CLO,/NO interaction. Nature, 315, 207-210. Hofmann, D.J., J.W. Harder, S.R. Rolf, and J.M. Rosen. 1987. Balloonborne observations of the development and vertical structure of the Antarctic ozone hole in 1986. Nature, 326, 59-62. McElroy, M.B., R.J. Salawitch, S.C. Wofsy, and J.A. Logan. 1986. Reductions of Antarctic ozone due to synergistic interactions of chlorine and bromine. Nature, 321, 759-762. Solomon, S., R.R. Garcia, F.S. Rowland, and D.J. Wuebbles. 1986. On the depletion of Antarctic ozone. Nature, 321, 755-758. Stolarski, R.S., A.J. Krueger, M.R. Schoeber!, R.D. Peters, P.A. Newman, and J.C. Alpert. 1986. Nimbus 7 SB(JVITOMS measurements of the springtime Antarctic ozone hole. Nature, 322, 808-811.
AN1ARCTIC JOURNAL
