Reporter 446, 7 February 2000

Mount models show how the wind blows

Model-making environmental researchers are building scale replicas of hills and mountains to help understand how high peaks cause severe weather.

Unpredictable windstorms in mountainous regions can tear down forests and cause airports problems. Placing miniature versions in a wind tunnel helps researchers understand how these effects occur.

"Hills produce a drag force on air flowing over them which current weather models struggle to predict," said the school of the environment's Simon Vosper. "Met office computers study patterns on a much larger scale but the data we produce takes local topography into account."

Mini-me: Researcher Dr Samantha Arnold rests after scaling another mountain

The model hills are made of aluminium and are packed with sensors to measure tiny air pressure fluctuations caused by air flowing over their surface. Temperatures in the wind tunnel are adjusted to mimic variations of air density and temperature with altitude in the real atmosphere.

‘Ground level’ wind is supplied at about 10 degrees C with wind tunnel air temperatures just a metre higher reaching an uncomfortable 80 degrees C.

This ‘stratification’ helps the researchers simulate typical atmospheric wind and temperature profiles, said Dr Vosper.

"Hills produce turbulence and waves which can propagate high into the atmosphere and for long distances downwind," he said. "Modelling this in the wind tunnel helps us understand the importance of these processes in the real atmosphere."

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