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Clear cooling effect: wind screen on the Rhône glacier in Switzerland creates cold air cushion

08.12.2008
By constructing a wind screen on the Rhône glacier in Switzerland, cold downwinds, which normally pass unhindered into the valley, can be intercepted and collected, thus creating a cold air cushion at the wind screen and in its close vicinity.

"Our test wind screen set up on the Rhône glacier resulted in a definite cooling of the air near the surface, with the drop in temperature being up to three degrees centigrade," reported Professor Hans-Joachim Fuchs of the Institute of Geography of the Johannes Gutenberg University Mainz.

"We also suspect that this could make it possible to slow down the melting rate of the ice. However, although we were able to observe this phenomenon, we are unable to offer any clear proof of it.” Together with 27 geography students, Professor Fuchs on Friday night presented the results of a project study during which the participants investigated the effects of global climate change on the Rhône glacier and developed solutions to this problem.

For this purpose, the students spent 10 days in the Wallis region in August 2008 and set up a wind screen with a length of 15 meters and a height of three meters. Over a period of six days, eleven digital measuring stations were used to record 95,000 measurement values to determine the air temperature directly at the wind screen, in its immediate vicinity, and at a distance from it. The data evaluation showed that the cooling effect was greatest when the sky was clear and there was a prevailing downwind. The temperatures within the wind screen were on average 1.5 to 2 degrees lower at night than the temperatures outside the wind screen. The maximum temperature difference recorded was as much as 3 degrees centigrade. "The further away the stations were from the wind screen, the higher the temperature measured," Fuchs reported. "This is a very definite, well-defined and above all consistent trend, which shows that the wind screen experiment worked."

Even on days with low pressure weather conditions, characterized by strong cloud cover and rain, with the wind coming from the south-west, the night-time temperatures inside the wind screen were 0.8 to 1 degree centigrade lower than outside the wind screen. Although the temperatures inside the wind screen area were generally lower during the day, the effect was not as clear as it was at night, as other influences such as direct solar radiation had an effect on the measuring stations. "The effectiveness of the wind screen would surely have been even greater if we had had stable high-pressure weather conditions with stronger, catabatic glacier winds," Fuchs added.

For technical reasons, it was not possible to measure the temperature of the ice surface with special infrared devices. Consequently, no data about the cooling of the glacier ice is available. "We were able to observe, though, that the hardness of the ice in the vicinity of the wind screen remained approximately the same throughout the day, while outside the wind screen, the ice crystals melted on the surface and the hardness decreased." Further observations of the project team support the estimate that the melting rate decreased in the vicinity of the wind screen.

A survey among visitors to the Rhône glacier also formed part of the project study. Although it was concluded that most of the 230 respondents were aware of climate change, they had no knowledge about the possible consequences and dangers. Against this background, the team designed a learning path called "Seeing and understanding the glacier", which runs along a kilometer-long footpath to a famous ice grotto. The grotto is visited by up to 1,500 tourists per day during the summer months. In addition, a folder was designed to inform people about the glacier, the way it is changing as well as the possible effects of climate change. Both the learning path and the folder were financed by a Swiss company.

Another sub-project was the educational film produced by the students of Mainz university using professional equipment, which is to be shown to the public on 6 February 2009.

"The test wind screen is, of course, much too small for a glacier. However, as it showed a clear cooling effect, this provides a starting point for further ideas and improvements to the construction. The students have already submitted recommendations in this regard." Project manager Fuchs also pointed out that this is merely a matter of treating the symptoms, while treating the cause remains the "top priority." According to Professor Fuchs, however, the glacier is retreating too quickly to wait until there is global insight into climate protection. "Most of our drinking water reserves are still bound in the glacier ice, but how long will this still be the case?"

Prof Dr Hans-Joachim Fuchs | alfa
Further information:
http://www.uni-mainz.de

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