Katabatic wind in Adélie Land
Halley Bay (United Kingdom), Dumont D'Urville (France), Syowa (Japan), and Casey and Mawson (Australia) with the cooperation of the personnel at these stations. The sampler consists of a small pump that fills a plastic bag with air at a constant rate. The bag is periodically emptied by a compressor into a pressure vessel until the required amount of air (about 360 liters) is collected. Airborne sampling will be conducted by piggybacking on VXE-6 LC-130 flights following the releases in January and September 1984. These samplers will strip out any heavy methanes that may be present in the air onto activated charcoal at liquid nitrogen temperature. The past season (1982-1983) was used to field-test prototype whole-air and cryogenic samplers. After collection, the samples will be returned to Los Alamos for analysis. The tracer data will be interpreted in conjunction with meteorological data to define the path taken by the tracer from the release point to the sampling location. Other participants in this effort include P. R. Guthals, A. Mason, and W. Efurd. This project is supported by National Science Foundation grant DPP 81-1562 and by the U.S. Department of Energy. Los Alamos National Laboratory is operated by the University of California for the U.S. Department of Energy.
Katabatic wind in Adélie Land C. WENDLER and Y. KODAMA Geophysical Institute University of Alaska Fairbanks, Alaska 99701
A. POGGI* University of Grenoble Grenoble, France
No other single phenomenon has such a strong influence on the climate of a whole continent, as the katabatic wind has on Antarctica. Because the reflectivity of snow is high, even during the summer, little energy is absorbed at the snow surface, the radiation budget is negative most of the time, and the air above the snow is cooled. As a consequence, a thin layer of air is steadily moving under the force of gravitation from the high plateaus toward the periphery of Antarctica. Although the katabatic wind has been described and studied for many years (starting with Mawson 1915) better understanding of the phenomenon has been hampered by a lack of observational data. It was possible to obtain either fixed-point data from a manned station on a year-round basis or data from a traverse that might have followed a "trajectory" of the wind, but the latter ones were not collected simultaneously at different places on the same slope. * Deceased March 1983.
236
References Cunningham, W. C., and W. H. Zoller. 1981. The chemical composition of remote area aerosols. Journal of Aerosol Science, 12, 367-384. Delmas, R. J. 1982. Antarctic sulphate budget. Nature, 299, 677-678. Fowler, M. M., and S. Barr. In press. A long range atmospheric tracer field test. Atmospheric Environment.
Hogan, A. W., and S. Barnard. 1978. Seasonal and frontal variation in Antarctic aerosol concentrations. Journal of Applied Meteorology, 17, 1458-1465. Maenhaut, W., W. H. Zoller, and D. C. Coles. 1979. Radionuclides in the South Pole atmosphere. Journal of Geophysical Research, 84, 3131-3138. Parish, T. R. 1982. Surface airflow over East Antarctica. Monthly Weather Review, 110, 26-32. Radke, L. F. 1982. Sulphur and sulphate from Mt. Erebus. Nature, 299, 710-712. Rubin, M. J., and W. S. Weyant. 1963. The mass and heat budget of the Antarctic atmosphere. Monthly Weather Review, October-December, 487-493. U.S. Department of Commerce. 1982. Geophysical monitoring for climatic change (Number 10 summary report 1981). Washington, D.C.: U.S.
Government Printing Office.
With the advance of technology in unmanned automatic weather stations (Aws), this deficiency in data collection could be overcome. Therefore, a joint U.S.-French experiment was designed in Adélie Land, where strong downslope winds are observed nearly continuously (Mather and Miller 1967). The United States concentrated their measurements on the upper slopes while the French made their measurements in the coastal areas and telemetered their data to the year-round manned station at Dumont d'Urville. The goals and results obtained so far have been previously described (André et al. in press; Gosink 1982; Poggi et al. 1982; Wendler and Kodama in press; Wendler, Kodama, and Poggi 1982; Wendler and Poggi 1980) so we will concentrate in this review on the work carried out during the last year. In the summer season of 1982-1983, a traverse with Expedition Polaries Francaises was made to service the previously installed AWS and to establish one new station. Over-snow vehicles were used because the area is too rough—large sastrugi are formed by the strong winds (figure 1)—to carry out landings with an LC-130 on an unprepared skiway. Besides the servicing of the stations, our scientific goal was to obtain measurements of the boundary layer during the traverse. Because our automatic weather stations measure meteorological parameters at only one height (about 3 meters above the surface) and the French are using 20-meter towers with five levels of instrumentation, measurements in the boundary layer were limited to the lower levels. To extend these data, the French (Sennequier personal communication) made measurements during January 1983 at a fixed station (D10) near the coast, using drones and balloons, while at the same time we moved up slope from sea level to 2,450-meter altitude, making measurements during the traverse with an air-sonde system, which was carried either by kite or by balloon. ANTARCTIC JOURNAL
DOME C +-+ D- I e -10 -28 Ix
-30 -40
CL
-50 -60 -70
680 960
-gi
940
660 T640 620
360
120
Figure 1. Large sastrugi are observed in Adélie Land about 200 kilometers away from the coast at an altitude of about 1,500 meters.
Of the five AWS's installed to date, the lowest one is used for intercomparison with the French measurements, three are on the slopes of the antarctic plateau at 1,560-, 2,130-, and 2,450meter altitudes, and one is located on top of Dome C (3,280 meters). Dome C is the highest point in the area and was chosen for an ice-drilling experiment. The distance from Dumont d'Urville is 1,080 kilometers. The area is totally flat and the adjacent slopes are inclined on the order of 1:10 4 (Williams personal communication). For more geographical details of the AWS sites, see the table. The monthly mean meteorological elements measured at D10 and Dome C in 1982 are shown in figure 2. The climatic conditions at Dome C are very different when compared to D10 and the rest of the slope stations. Temperatures at Dome C are about 45°C lower than D10 and D57 in the winter. This tern-
I2-
8 JAN FEB MAR APR MAY JJN JUL AUM SEP OCT NOV DEC
Figure 2. Temperature, pressure, wind speed, and wind direction for a coastal (Dl 0) and an inland station (Dome C) in Adélie Land. ("m/s" denotes meters per second; "mb' denotes millibar.)
perature gradient is greater than the adiabatic lapse rate and is related to the gravity flow (Ball 1956; Mahrt in press). The temperature at Dome C dropped to a minimum of —84.5°C, while at D10 temperatures below - 40°C were never observed. Figure 2 shows that the resultant wind direction at Dome C is fluctuating but at the coastal station it is very consistent (mean annual wind constancy 0.9). The wind speeds at Dome C are
Geographic setting of the automatic weather stations in Adélie Land Station
Location
66°42'S 139°48'E 67°23'S 138°43'E 68°1 l's 137°32'E 70°01 'S 134°43'E 74°30'S 123000'E
D10 D47 D57 D80
Dome C
Height Distance from Slope (in meters) Dumont d'Urville (in kilometers) 240 1,560 2,103 2,450 3,280
10 110 210 440
2
>< 10-2
6 >< 10 6 x 10 1 x 10
Azimuth of maximum upsiope
210° 210° 210° 210°
1,080
a Dome C, the highest point in the region, is flat; the adjacent slopes are inclined on the order of 1:10
1983 REVIEW
237
D57
Air Cooling Rate 19 cal cm Radiation Budget 31 cal cm-2
017:45 • 23:40
500 400 E IUj
300 200 100 0
-20 -15 -10 TEMPERATURE (°C)
I I I I I 120 140 10 18 20 WIND WIND SPEED (MIS) DIRECTION (°)
Figure 3. Profile measurements of temperature, wind speed, and wind direction through the boundary layer. These data were obtained with an air-sonde system and recorded on Hewlett-Packard equipment. ("m" denotes meter; "cal cm- 2 " denotes calories per square centimeter; "m/s! ' denotes meters per second.)
extremely low relative to other stations, showing no seasonal variations. Our boundary measurements obtained vertical profiles of dry-bulb and wet-bulb temperatures, atmospheric pressure, wind speed, and direction. These are being used to understand better the physical structure of the katabatic wind layer. An example is given in figure 3, which shows the results of two soundings at D57 on 20 January 1983. The temperature profile during the evening (1745 local standard time) shows lapse conditions below the height of 200 meters, and a small inversion, which might be a remnant from the previous day, can be seen at about 280 meters. Wind 'speed profiles for the same sounding do not show any distinctive maximum in the boundary layer. Near midnight (2340) the inversion is fully developed in the lowest 150 meters, and a distinctive maximum wind speed appears at the same height. Wind direction changes in the inversion layer are counterclockwise and are almost constant in the layer above. The radiation budget was measured between these two soundings, and it was -31 calories per square centimeter for this period; 19 calories per square centimeter were needed to cool the air in the lowest 300 meters from early evening to midnight. Hence, the radiatidn budget can easily explain the developing of the strong surface inversion during the night in the summer. This diurnal cycle in establishing and destroying of the surface inversion also explains the corresponding strong diurnal cycle in wind speed, which is observed in the coastal areas during the summer, showing a minimum in the early afternoon (Wendler and Kodama in press). This study was supported by National Science Foundation grant DPP 81-00161. Our thanks go to many individuals of the U.S. Antarctic Research Program as well as Expeditions Polaires
238
Francaises (Vaugelade and R. Guillard), and to C. Weller for his valuable comments. Our special thanks go to the other members of the traverse team, whose helpfulness and dedication made this work not only possible but very delightful. They are: C. Busicchia, P. Laffont, B. Piccot, M. Pourchet, M. Savage, D. Simon, and J . Wiget. References André, J. C., P. L. Blaix, D. Delaunary, J. Gosink, Y. Kodama, A. Poggi, and C. Wendler. In press. Interaction Atmosphere-Glace-Ocean en Antarctique. La Meteorologie. Ball, F. K. 1956. The theory of strong katabatic winds. Australian Journal of Physics, 9, 373-386. Gosink, J. 1982. Measurements of katabatic winds between Dome C and Dumont d'Urville. Pure and Applied Geophysics, Vol. 120, 503-526. Mahrt, L. In press. Momentum balance of gravity flows. Journal of Atmospheric Science.
Mather, K. B., and C. S. Miller. 1967. Notes on topographic factors affecting the surface wind in Antarctica, with special reference to katabatic winds and bibliography. (UAG R-189. Geophysical Institute Report). Fairbanks:
University of Alaska Press. Mawson, D. 1915. The home of blizzard, being the story of the Australian Antarctic Expedition 1911-1914. London: Heinemann. Poggi, A., D. Delaunary, H. Hallot and C. Wendler. 1982. Interactions Atmosphere-Glace-Ocean en Antarctique del'est. Proceedings of the Argos Users Conference, Paris, April 1982. Sennequier, C. 1983. Personal communication. Wendler, C., and Y. Kodama. In press. On the climate of Dome C, Antarctica in relation to its geographical setting. Journal of Climatology. Wendler, C., Y. Kodama, and A. Poggi. 1982. Climate of Dome C. Antarctic Journal of the U.S., 17(5), 201-203. Wendler, G., and A. Poggi. 1980. Measurement of the katabatic wind in Antarctica. Antarctic Journal of the U.S., 15(5), 193-195. Williams, I. 1982. Personal communication.
ANTARCTIC JOURNAL
Katabatic wind in Adélie Land C. WENDLER and Y. KODAMA Geophysical Institute University of Alaska Fairbanks, Alaska 99701
A. POGGI* University of Grenoble Grenoble, France
No other single phenomenon has such a strong influence on the climate of a whole continent, as the katabatic wind has on Antarctica. Because the reflectivity of snow is high, even during the summer, little energy is absorbed at the snow surface, the radiation budget is negative most of the time, and the air above the snow is cooled. As a consequence, a thin layer of air is steadily moving under the force of gravitation from the high plateaus toward the periphery of Antarctica. Although the katabatic wind has been described and studied for many years (starting with Mawson 1915) better understanding of the phenomenon has been hampered by a lack of observational data. It was possible to obtain either fixed-point data from a manned station on a year-round basis or data from a traverse that might have followed a "trajectory" of the wind, but the latter ones were not collected simultaneously at different places on the same slope. * Deceased March 1983.
236
References Cunningham, W. C., and W. H. Zoller. 1981. The chemical composition of remote area aerosols. Journal of Aerosol Science, 12, 367-384. Delmas, R. J. 1982. Antarctic sulphate budget. Nature, 299, 677-678. Fowler, M. M., and S. Barr. In press. A long range atmospheric tracer field test. Atmospheric Environment.
Hogan, A. W., and S. Barnard. 1978. Seasonal and frontal variation in Antarctic aerosol concentrations. Journal of Applied Meteorology, 17, 1458-1465. Maenhaut, W., W. H. Zoller, and D. C. Coles. 1979. Radionuclides in the South Pole atmosphere. Journal of Geophysical Research, 84, 3131-3138. Parish, T. R. 1982. Surface airflow over East Antarctica. Monthly Weather Review, 110, 26-32. Radke, L. F. 1982. Sulphur and sulphate from Mt. Erebus. Nature, 299, 710-712. Rubin, M. J., and W. S. Weyant. 1963. The mass and heat budget of the Antarctic atmosphere. Monthly Weather Review, October-December, 487-493. U.S. Department of Commerce. 1982. Geophysical monitoring for climatic change (Number 10 summary report 1981). Washington, D.C.: U.S.
Government Printing Office.
With the advance of technology in unmanned automatic weather stations (Aws), this deficiency in data collection could be overcome. Therefore, a joint U.S.-French experiment was designed in Adélie Land, where strong downslope winds are observed nearly continuously (Mather and Miller 1967). The United States concentrated their measurements on the upper slopes while the French made their measurements in the coastal areas and telemetered their data to the year-round manned station at Dumont d'Urville. The goals and results obtained so far have been previously described (André et al. in press; Gosink 1982; Poggi et al. 1982; Wendler and Kodama in press; Wendler, Kodama, and Poggi 1982; Wendler and Poggi 1980) so we will concentrate in this review on the work carried out during the last year. In the summer season of 1982-1983, a traverse with Expedition Polaries Francaises was made to service the previously installed AWS and to establish one new station. Over-snow vehicles were used because the area is too rough—large sastrugi are formed by the strong winds (figure 1)—to carry out landings with an LC-130 on an unprepared skiway. Besides the servicing of the stations, our scientific goal was to obtain measurements of the boundary layer during the traverse. Because our automatic weather stations measure meteorological parameters at only one height (about 3 meters above the surface) and the French are using 20-meter towers with five levels of instrumentation, measurements in the boundary layer were limited to the lower levels. To extend these data, the French (Sennequier personal communication) made measurements during January 1983 at a fixed station (D10) near the coast, using drones and balloons, while at the same time we moved up slope from sea level to 2,450-meter altitude, making measurements during the traverse with an air-sonde system, which was carried either by kite or by balloon. ANTARCTIC JOURNAL
DOME C +-+ D- I e -10 -28 Ix
-30 -40
CL
-50 -60 -70
680 960
-gi
940
660 T640 620
360
120
Figure 1. Large sastrugi are observed in Adélie Land about 200 kilometers away from the coast at an altitude of about 1,500 meters.
Of the five AWS's installed to date, the lowest one is used for intercomparison with the French measurements, three are on the slopes of the antarctic plateau at 1,560-, 2,130-, and 2,450meter altitudes, and one is located on top of Dome C (3,280 meters). Dome C is the highest point in the area and was chosen for an ice-drilling experiment. The distance from Dumont d'Urville is 1,080 kilometers. The area is totally flat and the adjacent slopes are inclined on the order of 1:10 4 (Williams personal communication). For more geographical details of the AWS sites, see the table. The monthly mean meteorological elements measured at D10 and Dome C in 1982 are shown in figure 2. The climatic conditions at Dome C are very different when compared to D10 and the rest of the slope stations. Temperatures at Dome C are about 45°C lower than D10 and D57 in the winter. This tern-
I2-
8 JAN FEB MAR APR MAY JJN JUL AUM SEP OCT NOV DEC
Figure 2. Temperature, pressure, wind speed, and wind direction for a coastal (Dl 0) and an inland station (Dome C) in Adélie Land. ("m/s" denotes meters per second; "mb' denotes millibar.)
perature gradient is greater than the adiabatic lapse rate and is related to the gravity flow (Ball 1956; Mahrt in press). The temperature at Dome C dropped to a minimum of —84.5°C, while at D10 temperatures below - 40°C were never observed. Figure 2 shows that the resultant wind direction at Dome C is fluctuating but at the coastal station it is very consistent (mean annual wind constancy 0.9). The wind speeds at Dome C are
Geographic setting of the automatic weather stations in Adélie Land Station
Location
66°42'S 139°48'E 67°23'S 138°43'E 68°1 l's 137°32'E 70°01 'S 134°43'E 74°30'S 123000'E
D10 D47 D57 D80
Dome C
Height Distance from Slope (in meters) Dumont d'Urville (in kilometers) 240 1,560 2,103 2,450 3,280
10 110 210 440
2
>< 10-2
6 >< 10 6 x 10 1 x 10
Azimuth of maximum upsiope
210° 210° 210° 210°
1,080
a Dome C, the highest point in the region, is flat; the adjacent slopes are inclined on the order of 1:10
1983 REVIEW
237
D57
Air Cooling Rate 19 cal cm Radiation Budget 31 cal cm-2
017:45 • 23:40
500 400 E IUj
300 200 100 0
-20 -15 -10 TEMPERATURE (°C)
I I I I I 120 140 10 18 20 WIND WIND SPEED (MIS) DIRECTION (°)
Figure 3. Profile measurements of temperature, wind speed, and wind direction through the boundary layer. These data were obtained with an air-sonde system and recorded on Hewlett-Packard equipment. ("m" denotes meter; "cal cm- 2 " denotes calories per square centimeter; "m/s! ' denotes meters per second.)
extremely low relative to other stations, showing no seasonal variations. Our boundary measurements obtained vertical profiles of dry-bulb and wet-bulb temperatures, atmospheric pressure, wind speed, and direction. These are being used to understand better the physical structure of the katabatic wind layer. An example is given in figure 3, which shows the results of two soundings at D57 on 20 January 1983. The temperature profile during the evening (1745 local standard time) shows lapse conditions below the height of 200 meters, and a small inversion, which might be a remnant from the previous day, can be seen at about 280 meters. Wind 'speed profiles for the same sounding do not show any distinctive maximum in the boundary layer. Near midnight (2340) the inversion is fully developed in the lowest 150 meters, and a distinctive maximum wind speed appears at the same height. Wind direction changes in the inversion layer are counterclockwise and are almost constant in the layer above. The radiation budget was measured between these two soundings, and it was -31 calories per square centimeter for this period; 19 calories per square centimeter were needed to cool the air in the lowest 300 meters from early evening to midnight. Hence, the radiatidn budget can easily explain the developing of the strong surface inversion during the night in the summer. This diurnal cycle in establishing and destroying of the surface inversion also explains the corresponding strong diurnal cycle in wind speed, which is observed in the coastal areas during the summer, showing a minimum in the early afternoon (Wendler and Kodama in press). This study was supported by National Science Foundation grant DPP 81-00161. Our thanks go to many individuals of the U.S. Antarctic Research Program as well as Expeditions Polaires
238
Francaises (Vaugelade and R. Guillard), and to C. Weller for his valuable comments. Our special thanks go to the other members of the traverse team, whose helpfulness and dedication made this work not only possible but very delightful. They are: C. Busicchia, P. Laffont, B. Piccot, M. Pourchet, M. Savage, D. Simon, and J . Wiget. References André, J. C., P. L. Blaix, D. Delaunary, J. Gosink, Y. Kodama, A. Poggi, and C. Wendler. In press. Interaction Atmosphere-Glace-Ocean en Antarctique. La Meteorologie. Ball, F. K. 1956. The theory of strong katabatic winds. Australian Journal of Physics, 9, 373-386. Gosink, J. 1982. Measurements of katabatic winds between Dome C and Dumont d'Urville. Pure and Applied Geophysics, Vol. 120, 503-526. Mahrt, L. In press. Momentum balance of gravity flows. Journal of Atmospheric Science.
Mather, K. B., and C. S. Miller. 1967. Notes on topographic factors affecting the surface wind in Antarctica, with special reference to katabatic winds and bibliography. (UAG R-189. Geophysical Institute Report). Fairbanks:
University of Alaska Press. Mawson, D. 1915. The home of blizzard, being the story of the Australian Antarctic Expedition 1911-1914. London: Heinemann. Poggi, A., D. Delaunary, H. Hallot and C. Wendler. 1982. Interactions Atmosphere-Glace-Ocean en Antarctique del'est. Proceedings of the Argos Users Conference, Paris, April 1982. Sennequier, C. 1983. Personal communication. Wendler, C., and Y. Kodama. In press. On the climate of Dome C, Antarctica in relation to its geographical setting. Journal of Climatology. Wendler, C., Y. Kodama, and A. Poggi. 1982. Climate of Dome C. Antarctic Journal of the U.S., 17(5), 201-203. Wendler, G., and A. Poggi. 1980. Measurement of the katabatic wind in Antarctica. Antarctic Journal of the U.S., 15(5), 193-195. Williams, I. 1982. Personal communication.
ANTARCTIC JOURNAL
