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Researching weather with a laser

Alexandra Pope, staff writer
November 13, 2011 — Scientists at the University of Western Ontario are using a powerful laser beam to collect weather data high in the atmosphere.

The light is reflected back into a spinning disc full of liquid mercury
The light is reflected back into a spinning disc full of liquid mercury

Satellites can't fly that low. Weather balloons can't fly that high. But a laser beam can reach the highest levels of the atmosphere -- and shed light on the dynamics that drive our weather.

That's exactly what scientists at the University of Western Ontario are hoping to do with the Purple Crow Lidar (laser radar).

The Purple Crow Lidar (PCL) is housed at Echo Base, Western's environmental science field station near London, Ontario.

The powerful laser emits pulses of light as bright as 1 million 75-watt bulbs. The beams are capable of reflecting off air molecules 100 km up, allowing researchers to measure the air density, temperature and composition (for example, water vapour) of the highest levels of the atmosphere.

The weather as we know it occurs in the lowest levels of the atmosphere, so why aim so high?

Increasingly, scientists are finding that what goes on in the upper atmosphere impacts the weather on the ground, says Robert Sica, lead investigator on the PCL project.

“20 years ago we talked about different regions of the atmosphere and discussed them in isolation,” he says. “Now we understand their synergy and how change at one height can cause changes at other heights.”

For example, scientists are finding that convection at the Earth's equator is so powerful, air, water vapour, ozone and other important chemicals are thrown out towards the poles, affecting the weather in those regions.

“A lot of the water vapour we measure here is water vapour that was brought to us essentially from the rainforest by the convective systems down there,” Sica explains.

PCL researchers are hoping their data will contribute to improvements in long-range weather forecasting and provide insight into climate change.

For more on the Purple Crow Lidar research, visit their blog.

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