Without going into too many scientific details, it can be said that the incredible strength of these winds is linked to the extreme cold in Antarctica. The colder the air is, the heavier it becomes. It becomes even heavier when it starts moving under the effect of the inclines of the polar ice-cap. This is the reason why they are called katabatic winds (from the Greek, kata, downwards). The blizzards are the most violent near the coast where the slopes become steeper. Another corollary strengthens the winds even further: the formation of approximately 1000 metres of a shaft of warm air at an altitude (extreme cooling of the air on the ground means that layers of air warm up at an altitude), which blocks the usual rising air. This means that the layers of air are pinned to the ground by this "lid" above, and as they have to respond to other forces, they begin to move in different directions from normal, usually upwards

The study of these katabatic winds has been carried out with particular care in preparation for the expedition. Because if we could highlight two factors which will be the gauges for this trans-Antarctic attempt succeeding or failing, they would be, first, the winds (presence, strength, direction, duration, etc.) and second, the use that can be made of them with the parafoil.

 

Winds gusts of 320 Km/h Have been recorded on Antarctica

That is why the co-operation between the expedition and the Belgian researcher, Hubert Gallée (UCL) has been so close; Gallée will in fact use his mathematical model on katabatic winds to enter new data provided by the expedition, let the computer work on it and then after days of calculations (that the computer generates by itself once the ad hoc data has been entered), produce new simulations for the winds (strength and direction) and temperatures throughout the assumed route of "South Through the Pole 1997-98" - at any time of the day or night. This is how the route was finally decided; the reason why Hubert and Dansercoer have opted for the Axel Heiberg glacier and down the polar plateau towards the Ross Sea (which does not appear to be the shortest route), is because the simulation produced by Gallée's mathematical model shows that the winds are likely to be of better quality and blowing in a more favourable direction all along that route.

The wind-chill factor

	Temperature (°C)
		0	-5	-10	-15	-20	-25	-30	-35	-40	-45	-50
	80	-20	-28	-36	-44	-52	-60	-68	-76	-84	-92	-100
	70	-19	-27	-35	-43	-51	-59	-67	-75	-83	-91	-99
	60	-19	-26	-34	-42	-50	-58	-66	-73	-81	-89	-97
	50	-18	-25	-33	-40	-48	-56	-63	-71	-79	-86	-94
	40	-16	-23	-31	-38	-45	-53	-60	-68	-75	-82	-90
	30	-13	-20	-27	-34	-41	-48	-55	-62	-70	-77	-84
	20	-10	-16	-23	-29	-35	-42	-48	-55	-61	-68	-74
	10	-3	-9	-15	-20	-26	-31	-37	-42	-48	-53	-59

You can see from this table that if for example the actual temperature is -20° and the wind is blowing at 56 km/h, the equivalent temperature becomes -47°; and if the actual temperature is -40°, with the wind blowing at 80 km/h, which is common enough in polar territory, the equivalent temperature becomes -84°, and so on.