Winter meteorological phenomena of the McMurdo area
Winter meteorological phenomena of the McMurdo area B. MURPHEY and A. HOGAN Atmospheric Sciences Research Center State University of New York Albany, New York 12222
A major portion of the last decade's antarctic meteorological research has been attempted at South Pole Station. While the south polar plateau has a unique and interesting meteorological regime, coastal Antarctica experiences more intense storms and exchange events, especially during winter and spring. A series of aerosol and ozone experiments were conducted [with the help of the Naval Support Force Antarctica (NSFA) meteorological observations] at McMurdo during 1983. These measurements and the meteorological observations allow estimation of exchange of particles and gases among atmospheric layers. A series of measurements, made by cooperating cosmic ray and infrasound observers during two previous winters established a firm basis for the wintering program. We retained the primary aerosol- and ozone-measuring instruments at the cosmic ray observatory and prepared a second observation station near Scott's Hut for sampling onshore winds. We used the phase contrast microscope and other apparatus in the biological laboratory for preliminary analyses of collected particle samples and returned the preserved samples to the United States in November 1983. Analysis of these particles with a scanning electron microscope and energy dispersive X-ray analysis continues. The preliminary results obtained indicate that tropospherestratosphere exchange is much more vigorous over the Ross Ice Shelf (78S) than over the interior of Antarctica. The radiation imbalance of the polar plateau causes such stable stratification of the polar troposphere that little exchange occurs, even when storms penetrate to the vicinity of the South Pole. Komyhr and Gras (1968), Oltmans and Komyhr (1976), and Oltmans (1980) found little evidence of exchange over the plateau after extensive ozone soundings and a long period of surface ozone observations. The surface ozone record at McMurdo shows frequent occurrence of stratospheric-tropospheric exchange, because
194
surface ozone concentration often increases by a factor of two or more, preceding and following storm events. This exchange seems especially vigorous in spring, as surface ozone concentrations of more than 100 parts per billion by volume were found following a September storm. Aerosol particles are exchanged horizontally, apparently from sea to ice, in the advective portion of the storm, when surface winds are accelerating. The surface aerosol concentration increases as the storm system approaches and surface wind increases. The concentration remains near maximum as the deep mixing occurs when the storm system dissipates and returns to typical values when the storm system has passed. Several case studies of ozone and aerosol variation around storms have been extracted from the winter observation record for thorough analysis and publication. The presence of nacreous clouds was noted by the observer during several clear periods in winter. Visual sightings of the cloud phenomena from the ground are rare in the Antarctic simply because there are so few observers. The stratospheric clouds have been sighted previously in both polar regions by the SAM H satellite system (McCormick et al. 1982). The clouds (also known as mother-of-pearls) persisted from several minutes to a few hours. Photographs were made of several nacreous cloud events. In general, most observations coincided with high pressure ridging across the continental plateau. The NSFA Meteorological Detachment soundings obtained in closest times proximity to the nacreous cloud sightings are being analyzed to determine if these high-level clouds can be associated with a specific stratosphere flow and temperature regime. This work has been supported by National Science Foundation grants DPP 79-05987 and DPP 83-14537. The authors express their thanks to Martin Pomerantz and Charles Wilson for their cooperation. The enthusiastic support of all personnel of the McMurdo Meteorological Office constitutes a major contribution to this work, and we offer them our thanks. References Komyhr, W.D., and R.D. Gras. 1968. Ozone sonde observations 1962-66, Vol. 2, ESSA Tech. Report ERL80-APCL3. Boulder, Cob.: ESSA. McCormick, Ml'., H.M. Steel, P. Hamill, W.P. Chu, and T.J. Swissler. 1982. Polar stratospheric cloud sightings by SAM II, Journal of Atmospheric Science, 39, 1387-1397. Oltmans, S.J. 1980. Clean air surface ozone measurements. Journal of Geophysical Research, 86, 1174-1180. Oltmans, S.J., and W.D. Komyhr. 1976. Surface ozone in Antarctica. Journal of Geophysical Research, 81, 5359-5364.
ANTARCTIC JOURNAL
A major portion of the last decade's antarctic meteorological research has been attempted at South Pole Station. While the south polar plateau has a unique and interesting meteorological regime, coastal Antarctica experiences more intense storms and exchange events, especially during winter and spring. A series of aerosol and ozone experiments were conducted [with the help of the Naval Support Force Antarctica (NSFA) meteorological observations] at McMurdo during 1983. These measurements and the meteorological observations allow estimation of exchange of particles and gases among atmospheric layers. A series of measurements, made by cooperating cosmic ray and infrasound observers during two previous winters established a firm basis for the wintering program. We retained the primary aerosol- and ozone-measuring instruments at the cosmic ray observatory and prepared a second observation station near Scott's Hut for sampling onshore winds. We used the phase contrast microscope and other apparatus in the biological laboratory for preliminary analyses of collected particle samples and returned the preserved samples to the United States in November 1983. Analysis of these particles with a scanning electron microscope and energy dispersive X-ray analysis continues. The preliminary results obtained indicate that tropospherestratosphere exchange is much more vigorous over the Ross Ice Shelf (78S) than over the interior of Antarctica. The radiation imbalance of the polar plateau causes such stable stratification of the polar troposphere that little exchange occurs, even when storms penetrate to the vicinity of the South Pole. Komyhr and Gras (1968), Oltmans and Komyhr (1976), and Oltmans (1980) found little evidence of exchange over the plateau after extensive ozone soundings and a long period of surface ozone observations. The surface ozone record at McMurdo shows frequent occurrence of stratospheric-tropospheric exchange, because
194
surface ozone concentration often increases by a factor of two or more, preceding and following storm events. This exchange seems especially vigorous in spring, as surface ozone concentrations of more than 100 parts per billion by volume were found following a September storm. Aerosol particles are exchanged horizontally, apparently from sea to ice, in the advective portion of the storm, when surface winds are accelerating. The surface aerosol concentration increases as the storm system approaches and surface wind increases. The concentration remains near maximum as the deep mixing occurs when the storm system dissipates and returns to typical values when the storm system has passed. Several case studies of ozone and aerosol variation around storms have been extracted from the winter observation record for thorough analysis and publication. The presence of nacreous clouds was noted by the observer during several clear periods in winter. Visual sightings of the cloud phenomena from the ground are rare in the Antarctic simply because there are so few observers. The stratospheric clouds have been sighted previously in both polar regions by the SAM H satellite system (McCormick et al. 1982). The clouds (also known as mother-of-pearls) persisted from several minutes to a few hours. Photographs were made of several nacreous cloud events. In general, most observations coincided with high pressure ridging across the continental plateau. The NSFA Meteorological Detachment soundings obtained in closest times proximity to the nacreous cloud sightings are being analyzed to determine if these high-level clouds can be associated with a specific stratosphere flow and temperature regime. This work has been supported by National Science Foundation grants DPP 79-05987 and DPP 83-14537. The authors express their thanks to Martin Pomerantz and Charles Wilson for their cooperation. The enthusiastic support of all personnel of the McMurdo Meteorological Office constitutes a major contribution to this work, and we offer them our thanks. References Komyhr, W.D., and R.D. Gras. 1968. Ozone sonde observations 1962-66, Vol. 2, ESSA Tech. Report ERL80-APCL3. Boulder, Cob.: ESSA. McCormick, Ml'., H.M. Steel, P. Hamill, W.P. Chu, and T.J. Swissler. 1982. Polar stratospheric cloud sightings by SAM II, Journal of Atmospheric Science, 39, 1387-1397. Oltmans, S.J. 1980. Clean air surface ozone measurements. Journal of Geophysical Research, 86, 1174-1180. Oltmans, S.J., and W.D. Komyhr. 1976. Surface ozone in Antarctica. Journal of Geophysical Research, 81, 5359-5364.
ANTARCTIC JOURNAL
