Katabatic Winds

Its name comes from the Greek, 'kata' meaning downwards, and this type of wind can be found across the Earth.

In the UK the weather situation that gives rise to most katabatic winds, is when a large slow moving high pressure, or anticyclone, sits over the country in late autumn, winter or early spring.

When this happens, especially with clear skies at night, the Earth loses a lot of its heat to space and the temperature falls quickly.

Imagine this happening in a Scottish or Welsh mountain valley. As the night goes by, the air close to the ground gets colder and colder, and often ends up as a large pool of cold dense air. This can then spill over the side of the mountain where gravity takes over. This cold wind drains down the mountainside to the valley below as a cold katabatic wind.

In this country these katabatic winds are generally quite light, in the order of five to ten mph, but around the world they can be very much stronger.

The most famous katabatic wind in Europe is the Mistral, which blows down the Rhône valley in southern France and out into the Mediterranean. It can become a very strong wind reaching speeds of 80 miles an hour as it funnels down over the Rhône delta and is generally at its strongest in winter and early spring.

But one of the strongest katabatic winds we experience on this planet blows in the Antarctic. Here the lowest layers of the air, sitting on some of the high plateaux, come into contact with the cold dense ice sheet. The air cools to very low temperatures and spills over the mountain ridges as a katabatic wind.

These Antarctic winds have been measured at over 200 miles and hour and are some of the strongest winds measured on our planet at ground level, outside those in some tornadoes.