Atmospheric boundary measurements in eastern Antarctica
into the Ross Sea and Marie Byrd Land area. This type of air mass is frequently associated with strong air flow over the Ellsworth and Queen Maud mountain ranges. It is suggested on the basis of the correlation between fine mode particles and ozone and continental antarctic air masses, that the fine transient mode of particles may arise from the entrainment of stratospheric or upper tropospheric air, perhaps driven by breaking waves associated with air flowing over the mountain barriers as suggested by Robinson et al. (1983). This work was supported by National Science Foundation grant DPP 82-19625. Thanks to A. Hogan for making ozone data available and to B. McKibben, A. Anger, and AG1 Crayne for help with the experiments.
Atmospheric boundary measurements in eastern Antarctica C. WENDLER
References Alt, S., P. Astapenko, and N.J. Ropar, Jr. 1959. Some aspects of the Antarctic atmospheric circulation in 1958. 1GY Word Data Center, A, iGYGeneral Report, Series No.4. Washington, D.C.: National Academy of Sciences. Greenfield, S.M. 1957. Rain scavenging of radioactive particulate matter from the atmosphere. Journal of Meteorology, 14, 115-125. Hogan, A., and S. Barnard. 1978. Seasonal and frontal variations in Antarctic aerosol concentrations. Journal of Applied Meteorology, 17(10), 1458-1465. Ito, T. 1983. Study on properties and origin of aerosol particles in the Antarctic atmosphere. Papers in Meteorology and Geophysics, 34(3), 151-219. (Meteorological Research Institute of Japan.) Robinson, E., D. Clark, D.R. Crom, and W.L. Bamesberger. 1983. Stratospheric tropospheric ozone exchange in Antarctica caused by breaking waves. Journal of Geophysical Research, 88, 19708-19720.
wind speed was observed at 120 meters, which is the so-called katabatic wind. The picture shown here is rather typical, and little variation was observed from day to day. The wind direction changes with height as well, turning somewhat to the left within boundary layer. This also is rather representative of the katabatic wind in the Southern Hemisphere. Besides these bound-
Geophysical Institute University of Alaska Fairbanks, Alaska 99701 J.C. ANDRE
Centre National tie Recherches Meteorologiques loulouse, Trance
A major field study in Adélie Land, Eastern Antarctica was carried out this year as a joint U.S.-French experiment. The goal was to obtain a better understanding of the boundary layer in Antarctica, with special attention being given to the katabatic wind. Long-term climatological and upper-air data could be obtained from Dumont d'Urville. There are, further, five automatic weather stations, which stretch from close to the coast to Dome C at the end. D-10 is the closest station, some 10 kilometers from Dumont d'Urville, while Dome C is some 1,080 kilometers inland at a height of 3,280 meters. These stations have given us climatological data along the icy slopes of Adélie Land for the last 6 years, on which we reported last year. For our intensive measuring period of about 40 days, three stations were occupied, two by the French and one by us, located some 5, 110, and 210 kilometers from the coastline. Balloons, air foils, and drones were used as carriers for our meteorological packages. The meteorological data were transmitted via radio to ground stations, where they were recorded on magnetic tape. Figure 1 shows the air foild, which is one of those used at the U.S. station. Some difficulties were experienced in very strong winds (above 20 meters per second), which could break the line. A typical morning profile obtained from these measurements is given in figure 2. A strong surface temperature inversion can be observed, which was established in the night, and is now beginning to erode. This is typical for most of Antarctica most of the time. The height of the inversion is about 500 meters. Within this inversion layer, a maximum 242
"I
Figure 1. An air foil, which will be used as a carrier for the meteorological package, is released at D-47, Adélie Land, Antarctica. ANTARCTIC JOURNAL
23 DECEMBER 1985. 0900
r-880
700-I I i I
H SO0 -1 £ I I I. I I I I
I ff50O
I / / \ 300—I J J )
100-J / /
E I I
800
I
L-300
I I 1-200
600
I I 1-100
-20 -15 0.5 1.0 1.5 0 10 20 100 150 200 250 Figure 2. Meteorological measurements of the atmospheric boundary layer at D-47, Adélie Land, Antarctica, 23 December 1986 09:00 hours. Presented are: A. temperature profile in degrees Celsius; B. humidity profile in grams of water per kilogram of air; C. wind speed in meters per second; and D. wind direction in degrees.
ary profile measurements, which were carried out daily for most of the 40-day observational period, two instrumented aircraft missions were flown, which covered the whole area from Dumont d'Urville to Dome C. Additional micrometeorological surface observations were carried out, including a heat-balance study. All data were recorded at 10-minute intervals on a Campbell Data Logger CR-7. It was found that the incoming solar radiation is the largest energy source, which can destroy the surface temperature inversion during the day. The albedo was found to be high, with a mean value of about 80 percent. It is a function of solar height, sastrugi height and direction, and cloudiness. With increasing solar distance, an increase in albedo was observed; a result previously reported and expected. Sastrugis produced a shadow pattern that was not symmetric about solar noon, and this could explain the diurnal variations in albedo which were unsymmetric about solar noon. Further, cloudiness and new snow fall increases the albedo, and during white-out conditions albedos as high as 94 percent were observed. In figure 3 the radiative fluxes for a totally clear day, both short and long wave are presented. Even though we have 22 hours of sunshine on 29 November 1985 at D-47, only 9 hours show a positive radiation balance, because most of the short-wave radiation is reflected. In addition, an interesting phenomenon was observed: with increasing cloudiness a more positive radiation balance is found, which is due to the great importance of longwave radiation. This is in contrast to the mid-latitudes, where the short-wave balance is the dominant force. Roughness parameters, which were calculated from our wind profile mast measurements, gave mean values of about 0.1 millimeter for Z,, for wind speeds below 10 meters per second. Above this wind speed, the roughness parameter increased about threefold, which is believed to be caused by drifting and blowing snow, common phenomena at higher wind speeds. This is in agreement with data recently collected on the Ekstrom Ice Shelf in Antarctica. Blowing snow was measured photoelectrically with a snow blowing device developed after Schmidt (1977). The mass flux of snow for a specific height varied with approximately the cube of the wind speed. The wind speed/mass flux calculations gave
1986 REVIEW
29 NOVEMBER 1985
1-700
/ -600
200H I I
1000
I
600-4 k 4 I
I
400
200
3 6 9 12 15 18 21 24 HOUR OF DAY Figure 3. The short wave incoming (A), the short wave reflected, (B), the infrared incoming (C), and outgoing radiation (D), in watts per square meter.
the best results for short time intervals (15 seconds). We are now in the process of calculating the annual mass flux of snow using the annual wind speed distribution at D-47 from the automatic weather stations; the mean annual wind speed is 12.8 meters per second. The temperature profile measurements from the mast and the humidity measurements made calculations of the sensible and estimates of the latent heat flux possible. During the day, the surface warms the air, while during the night the flux is in the opposite direction. This loss of energy during the night develops, of course, the well known temperature inversion. The latent heat fluxes are small, and iwth the exception of one period, when maritime air was advected, evaporation occurred. It is hoped that the surface energy-budget measurements, together with the profile measurements through the boundary layer and the measurements from the instrumented aircraft, will lead to a better understanding of the energetics of the katabatic wind. This study was supported by National Science Foundation grant DPP 84-13367. Our thanks go to many individuals of the U.S. Antarctic Research Program, as well as to the Expeditions Polaires Françaises. We are further grateful to Dr. Stearns' group (University of Wisconsin, Madison), who did a great job maintaining our automatic weather stations. Reference Schmidt, R.A. 1977. A system that measured blowing snow. (U.S. Department of Agriculture Forest Service research paper RM-194.)
243
Atmospheric boundary measurements in eastern Antarctica C. WENDLER
References Alt, S., P. Astapenko, and N.J. Ropar, Jr. 1959. Some aspects of the Antarctic atmospheric circulation in 1958. 1GY Word Data Center, A, iGYGeneral Report, Series No.4. Washington, D.C.: National Academy of Sciences. Greenfield, S.M. 1957. Rain scavenging of radioactive particulate matter from the atmosphere. Journal of Meteorology, 14, 115-125. Hogan, A., and S. Barnard. 1978. Seasonal and frontal variations in Antarctic aerosol concentrations. Journal of Applied Meteorology, 17(10), 1458-1465. Ito, T. 1983. Study on properties and origin of aerosol particles in the Antarctic atmosphere. Papers in Meteorology and Geophysics, 34(3), 151-219. (Meteorological Research Institute of Japan.) Robinson, E., D. Clark, D.R. Crom, and W.L. Bamesberger. 1983. Stratospheric tropospheric ozone exchange in Antarctica caused by breaking waves. Journal of Geophysical Research, 88, 19708-19720.
wind speed was observed at 120 meters, which is the so-called katabatic wind. The picture shown here is rather typical, and little variation was observed from day to day. The wind direction changes with height as well, turning somewhat to the left within boundary layer. This also is rather representative of the katabatic wind in the Southern Hemisphere. Besides these bound-
Geophysical Institute University of Alaska Fairbanks, Alaska 99701 J.C. ANDRE
Centre National tie Recherches Meteorologiques loulouse, Trance
A major field study in Adélie Land, Eastern Antarctica was carried out this year as a joint U.S.-French experiment. The goal was to obtain a better understanding of the boundary layer in Antarctica, with special attention being given to the katabatic wind. Long-term climatological and upper-air data could be obtained from Dumont d'Urville. There are, further, five automatic weather stations, which stretch from close to the coast to Dome C at the end. D-10 is the closest station, some 10 kilometers from Dumont d'Urville, while Dome C is some 1,080 kilometers inland at a height of 3,280 meters. These stations have given us climatological data along the icy slopes of Adélie Land for the last 6 years, on which we reported last year. For our intensive measuring period of about 40 days, three stations were occupied, two by the French and one by us, located some 5, 110, and 210 kilometers from the coastline. Balloons, air foils, and drones were used as carriers for our meteorological packages. The meteorological data were transmitted via radio to ground stations, where they were recorded on magnetic tape. Figure 1 shows the air foild, which is one of those used at the U.S. station. Some difficulties were experienced in very strong winds (above 20 meters per second), which could break the line. A typical morning profile obtained from these measurements is given in figure 2. A strong surface temperature inversion can be observed, which was established in the night, and is now beginning to erode. This is typical for most of Antarctica most of the time. The height of the inversion is about 500 meters. Within this inversion layer, a maximum 242
"I
Figure 1. An air foil, which will be used as a carrier for the meteorological package, is released at D-47, Adélie Land, Antarctica. ANTARCTIC JOURNAL
23 DECEMBER 1985. 0900
r-880
700-I I i I
H SO0 -1 £ I I I. I I I I
I ff50O
I / / \ 300—I J J )
100-J / /
E I I
800
I
L-300
I I 1-200
600
I I 1-100
-20 -15 0.5 1.0 1.5 0 10 20 100 150 200 250 Figure 2. Meteorological measurements of the atmospheric boundary layer at D-47, Adélie Land, Antarctica, 23 December 1986 09:00 hours. Presented are: A. temperature profile in degrees Celsius; B. humidity profile in grams of water per kilogram of air; C. wind speed in meters per second; and D. wind direction in degrees.
ary profile measurements, which were carried out daily for most of the 40-day observational period, two instrumented aircraft missions were flown, which covered the whole area from Dumont d'Urville to Dome C. Additional micrometeorological surface observations were carried out, including a heat-balance study. All data were recorded at 10-minute intervals on a Campbell Data Logger CR-7. It was found that the incoming solar radiation is the largest energy source, which can destroy the surface temperature inversion during the day. The albedo was found to be high, with a mean value of about 80 percent. It is a function of solar height, sastrugi height and direction, and cloudiness. With increasing solar distance, an increase in albedo was observed; a result previously reported and expected. Sastrugis produced a shadow pattern that was not symmetric about solar noon, and this could explain the diurnal variations in albedo which were unsymmetric about solar noon. Further, cloudiness and new snow fall increases the albedo, and during white-out conditions albedos as high as 94 percent were observed. In figure 3 the radiative fluxes for a totally clear day, both short and long wave are presented. Even though we have 22 hours of sunshine on 29 November 1985 at D-47, only 9 hours show a positive radiation balance, because most of the short-wave radiation is reflected. In addition, an interesting phenomenon was observed: with increasing cloudiness a more positive radiation balance is found, which is due to the great importance of longwave radiation. This is in contrast to the mid-latitudes, where the short-wave balance is the dominant force. Roughness parameters, which were calculated from our wind profile mast measurements, gave mean values of about 0.1 millimeter for Z,, for wind speeds below 10 meters per second. Above this wind speed, the roughness parameter increased about threefold, which is believed to be caused by drifting and blowing snow, common phenomena at higher wind speeds. This is in agreement with data recently collected on the Ekstrom Ice Shelf in Antarctica. Blowing snow was measured photoelectrically with a snow blowing device developed after Schmidt (1977). The mass flux of snow for a specific height varied with approximately the cube of the wind speed. The wind speed/mass flux calculations gave
1986 REVIEW
29 NOVEMBER 1985
1-700
/ -600
200H I I
1000
I
600-4 k 4 I
I
400
200
3 6 9 12 15 18 21 24 HOUR OF DAY Figure 3. The short wave incoming (A), the short wave reflected, (B), the infrared incoming (C), and outgoing radiation (D), in watts per square meter.
the best results for short time intervals (15 seconds). We are now in the process of calculating the annual mass flux of snow using the annual wind speed distribution at D-47 from the automatic weather stations; the mean annual wind speed is 12.8 meters per second. The temperature profile measurements from the mast and the humidity measurements made calculations of the sensible and estimates of the latent heat flux possible. During the day, the surface warms the air, while during the night the flux is in the opposite direction. This loss of energy during the night develops, of course, the well known temperature inversion. The latent heat fluxes are small, and iwth the exception of one period, when maritime air was advected, evaporation occurred. It is hoped that the surface energy-budget measurements, together with the profile measurements through the boundary layer and the measurements from the instrumented aircraft, will lead to a better understanding of the energetics of the katabatic wind. This study was supported by National Science Foundation grant DPP 84-13367. Our thanks go to many individuals of the U.S. Antarctic Research Program, as well as to the Expeditions Polaires Françaises. We are further grateful to Dr. Stearns' group (University of Wisconsin, Madison), who did a great job maintaining our automatic weather stations. Reference Schmidt, R.A. 1977. A system that measured blowing snow. (U.S. Department of Agriculture Forest Service research paper RM-194.)
243
