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Cape Denison, Eastern Antarctica, the windiest place on Earth
by Gerd Wendler and Uwe Radok
In 1911 the Australasian Antarctic expedition led by Douglas Mawson sailed to Antarctica to explore the area close to the magnetic South Pole. Mawson established his main station at Cape Denison (67.02° S, 142.68° E), in Commonwealth Bay (Fig.1). The ship encountered no sea ice in the coastal area and thus was able to reach the shore. The absence of sea ice might have been taken as an indication of strong winds from the continent, and indeed, the wind speeds observed for from February 1912 to October 1914 were the highest found anywhere on Earth close to sea level (Madigan 1929, Kidson 1946). Mawson (1915) reported on this in his popular description of the expedition properly entitled "The Home of the Blizzard". The wind speeds recorded by his expedition were doubted after returning from Antarctica and a recalibration of the "puff-ball" anemometer in a wind tunnel reduced the calibration constant for strong winds of up to 20%. It was later speculated that the corrections were excessive, but even after reducing the values, an annual mean wind speed of 19.1 ms-1 was calculated. The speeds were less severe during the summer months and had a very broad maximum during the rest of year. Hence, the maximum was not necessarily found in mid-winter. As the katabatic wind is driven by thermal contrast, this might be expected from the annual course of the temperature which displays a coreless winter (Wendler and Kodama 1993).
Some 40 years later the French established the station Port Martin, some 62 km to the west of Cape Denison. The wind conditions there were again extreme, and a mean annual wind velocity of 17.9 ms-1 was found (Boujon 1954). This indicated that these extraordinary strong katabatic winds were not limited to a specific site but dominate part of the coast, a fact also Parish (1981) pointed out while analyzing data from Mawson's sledding parties.
In 1952 Port Martin was destroyed by fire, and the French moved their base to a summer camp 64 km west of Port Martin on an island 2 km from the coast, Ile des Petrelles. Here, the mean annual wind speed was 10.5 ms-1, about half that measured at the other two stations. The French therefore chose this site for their IGY station Dumont d'Urville, which became the only station along the coast with a long and still continuing climataological record (Periard and Pettré 1993). Cape Denison and Port Martin were never occupied again on a year-round basis, and it was only with the advance of remote data sensing techniques that new climate data could be collected at these sites.
By 1980 automatic weather stations (AWS's) had been sufficiently advanced to be used in Antarctica (Stearns 1982). These stations measure temperature, humidity, atmospheric pressure, and wind speed and direction and are transmitting their data by satellite. An initial AWS array was established from close to Dumont d'Urville up to Dome C, at 3280 m altitude, and some 1080 km inland. Some 10 years later, the coastal station array shown in Fig.1 was set up. At Cape Denison we were able to locate and occupy the "Anemometer Hill" where Mawson's expeditions had carried out their wind observations. The winds speeds fom the new data collected there and at Port Martin were indeed very high (Wendler et al. 1997), while the stations to the east and west reported much less extreme conditions. However often our wind sensors did not survive the extreme winds and provided only a frequently broken record. These showed that the maximum speeds could occur in fall when an additional acceleration resulted from the thermal contrast between the already cold continent and the still ice-free ocean.
During the summer of 1994/95 very rugged anemometer built by Hydrotech (Taylor) in Washington became available and were installed at our stations. There for the first time we obtained year-round data. Cape Denison was confirmed as the windiest place on Earth close to sea level (Fig.2). Each of four consecutive months recorded a mean monthly wind speed in excess of 25 ms-1. June had the highest speed, 27.7 ms-1, and March the second highest wind speed with 27.2 ms-1, while eight months of the year had mean monthly wind speeds above 24 ms-1. For five months the maximum wind speeds exceeded 50 ms-1. The directional constancy was high throughout the year, and even its minimum in December remained well above 90%. A secondary minimum occurred in mid-winter; this may have been a feature of the 1995 winter only. Hurricane wind speeds (>32 ms-1) were observed during 19.9% of the time, and during 29.2% of the time in the winter months.
These extraordinary winds reflect, in addition to the gravitational force (Ball 1960, Radok 1973), a funneling of the flow by terrain features. The Adelie Land coast had emerged from model simulation of the antarctic surface winds as one of the major confluence regions (Parish and Bromwich 1987). A detailed model of this coastal region (Parish and Wendler 1991) provides wind data which are compared with our measurements in Fig.3. The model overestimates the annual mean wind speeds both to the west (D10) and to the east (Cape Webb) of Cape Denison, but general trends and the maximum at Cape Denison are in good agreement with the measurements.
Finally, the mean annual wind speed we measured in 1995 was 22.4 ms-1. This is 17% higher than the "corrected" wind speeds of Mawson's expedition, indicating that those corrections were overdone, as pointed out previously by Loewe (1972).
Acknowledgment
This study was supported by NFS Grant OPP 94-13879. Our thanks go to many people from the U.S. Coast Guard Cutter "Polar Star", US Antarctic Program and Expeditions Polaires Françaises, without whose help this study could not have been carried out. Blake Moore did the data reduction and Gunter Weller made valuable comments.
References
Ball, F. 1960. Winds on the icy slopes of Antarctica, in Antarctic Meteorology, 9-16, Pergamon, New York
Boujon, H. 1954. Les observations météorologiques de Port-Martin en Terre Adélie,. Fasc. I, Conditions atmosphériques en surface et en altitude du 14 Février 1950 au 14 Janvier 1951: Relevés quotidiens et commentaires, Expeditions Polaires Francaise, Series S, 5, 167 pp
Kidson, E. 1946. Discussions of observations, Australasian Antarctic Expedition 1911-1914, Scientific Report, Series B, VI, 120 pp
Loewe, F. 1972. The land of storms, Weather, 27, 110-121
Mawson, D. 1915. The Home of the Blizzard; being the story of the Australasian Antarctic Expedition 1911-1914, 438 pp., Heinemann, London
Parish, T. R. 1981. The katabatic winds of Cape Denison and Port Martin, Polar Record, 20, 525-532
Parish, T. R., and D. H. Bromwich. 1987. The surface windfield over the Antarctic ice sheets, Nature, 328, 51-54
Parish, T. and G. Wendler 1991. The katabatic wind regime in Adélie Land. International Journal of Climatology, 11, 97-107
Periard, C., and P. Pettré 1993. Some aspects of the climatology of Dumont d'Urville, Adélie Land, Antarctica, International Journal of Climatology ,13, 313-327
Radok, U.1973. On the energetics of surface winds over the Antarctic Ice Cap. Energy fluxes over polar surfaces, in Proceedings of IAMAP, IAPSO/SCAR/WMO Symposium, Moscow, Tech. Note 179, pp. 69-100, World Meteorological Organization, Geneva
Stearns, C. 1982. Automatic weather station technical manual. Department of Meteorology, University of Wisconsin, Madison.
Wendler, G., and Y. Kodama 1993. The kernlose winter in Adélie Land, Special AGU publication of the Antarctic Research Series, Antarctic Meteorology and Climatology: studies based on automatic weather stations, Vol.61, 130-147
Wendler, G., C. Stearns, G. Weidner, G. Dargaud and T. Parish 1997: On the extraordinary winds of Adélie Land. Journal of Geophysical Research 102, D4 , 4463-4474
Figure Captions
1. Area map of Adélie Land, Eastern Antarctica
2. Annual course of wind speed, wind directional constancy, and frequency of hurricane force winds (>32 ms-1) Cape Denison, Commonwealth Bay
3. Measured and modeled annual mean wind speed for coastal stations in Adélie Land between 139°E and 147°E. The modeled values were deduced from figure 5c by Parish and Wendler (1991)
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