The most recent soundings reported here were con-ducted by Messrs. Olson, Martell, and Kiernan, whowere in the field from January 2 to February 8, 1974.This research was supported by National ScienceFoundation grant Gv-28077.

Reference

Hofmann, D. J., R. G. Pinnick, and J. M. Rosen. 1973.Aerosols in the south polar stratosphere. Antarctic Jour-nal of the U.S., VIII(4): 183-185.

Atmospheric aerosol investigations

AUSTIN W. HOGANAtmospheric Sciences Research Center

State University of New York at AlbanyScotia, New York 12302

Antarctica provides many unique situations in whichto determine physical properties of the atmosphericaerosol. During the 1973-1974 summer, several deter-minations of the concentration and size of particlesin the antarctic atmosphere were done at McMurdo,Siple, and South Pole stations. Data analysis con-tinues with the cooperation of Mr. D. Nelson, NationalOceanic and Atmospheric Administration (NOAA),and the voluntary efforts of Mr. M. Fussell, satellitetracker at McMurdo.

The background aerosol concentration appears tobe about 50 to 75 particles per cubic centimeter onthe polar plateau, and about 125 particles per cubiccentimeter in Ellsworth Land. Maritime air, fromthe Ross Sea, contains about 300 particles per cubiccentimeter; this amount is similar to more temperatemaritime regions.

Two interesting aerosol events occurred during thefield program. Aerosol concentration rose to about500 to 1,200 particles per cubic centimeter, while theapparent size decreased to less than 5x10 7 centi-meters in radius during both of these occasions, andreturned to the original background levels within 48hours. Each of these events accompanied a loweringof the antarctic tropopause, and each ceased when thetropopause level rose again. Similar events have beenreported in strong katabatic winds at Mirnyy Station(Soviet Union).

Formvar replicas of precipitating ice crystals, ob-tained at the South Pole, show the predominant crys-tal types as columnar, as hollow columnar, or as pris-matic columnar. Sometimes very small crystals of tri-angular and of hexagonal form (often called "dia-mond dust") were observed. NOAA soundings at the

South Pole show that a layer, saturated with ice, al-most always is present at the 650- to 600-millibar levelover the polar plateau. Since ice crystal precipi ationwas observed only from this saturated layer henglaciated bands were present aloft, it is hypoth sizedthat smaller crystals, descending from these higherlevels, nucleate these crystals, and that heterogeneous,freezing nuclei were absent from the polar r ion.

A period of drifting snow acompanying winds of 48kilometers per hour occurred at Siple Station. Visualobservations showed that the drifting snow was eingintercepted by the roughened surface snow in thecamp area. Several formvar replicas were made of thedrifting snow grains at points upwind of the camF andat the camp. Measurement of the volumes of nowreplicated showed the camp was collecting 75 percentof the snow passing over the area.

Vehicle tracks in the camp area apparently rou henthe snow surface sufficiently to cause a slowing o thenear surface wind. This diminished wind speed al owsthe suspended snow grains to settle to the sur ace.When sufficient snow is collected to smooth the sur-face, the accumulation zone advances downwind.Calculation shows that vehicle tracks can cause ac-cumulation of 7 centimeters of snow per windy day;this can be a relatively great source of snow accunu-lation in the camp area as the surface is reroughnedbetween windy periods.

This research was supported by National ScienceFoundation grant GA-032502.

Atmospheric processes and energtransfers at the South Pole

JOHN J . CARROLL,KINSELL L. COULSON, and

BRUCE W. FITCHUniversity of CaliforniaDavis, California 95616

The objectives of this project are to: (1) asthe extent to which Antarctica constitutes a heat sfor atmospheric circulation; (2) obtain informaton the aerosol content of the atmosphere, and itspossible secular increase, by measurements of hepolarization of light from the sunlit sky. During 19 !3..1974) the project's first year, a preliminary inst U-mentation system was developed and tested in heantarctic environment. A relatively large number ofpreliminary data was obtained. The three participl itsspent January 10 to February 13, 1974, in Antarci cato make measurements.

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