Space Lasers Take To The Winds

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Scientists at the Global Hydrology and Climate Centre are studying a type of radar that uses laser light instead of microwaves to provide high-quality snapshots of the winds that travel the globe. Knowing the wind's speed and direction over large areas could help meteorologists answer the riddle of tomorrow's weather further in advance, saving lives and benefiting many areas of the world's economy -- particularly air travel.

"Lidar," or Light Detection and Ranging, is a technique that's been used for years to study the atmosphere from the ground. But now researchers are touting the benefits of lidar from space.

Dr. Michael Kavaya, a scientist at the Global Hydrology and Climate Centre (GHCC) in Huntsville, USA, champions space-based laser sensing of the Earth's winds because of the "immediate benefit of wind sensors orbiting the Earth."

"Orbiting wind sensors could help airline pilots avoid headwinds, leading to savings on fuel," explains Kavaya. According to one study, these savings could amount to $100 million to $200 million per year for airlines.

Fuel savings just scratch the surface of what lidar can accomplish.

Graphic showing sea-surface wind speeds

"On-board lidar sensors on each airplane would be valuable for microburst wind shear and clear-air turbulence warnings. These are significant threats to passengers' safety," says Kavaya.

"Clear air turbulence occasionally hurts people and even kills them. There have been a few deaths in the past couple of years - people don't have their seat belts on and they're thrown into the ceiling, or the food cart is thrown at them. Microburst wind shears can cause accidents on landing or take off "

Lidar may also prove invaluable for monitoring the flow of water through rivers, for improving weather forecasts, and even for understanding the complex El Niño/La Niña phenomenon.

Light Detection and Ranging

Lidar works by beaming pulses of laser light through the atmosphere and detecting the light reflected back by dust and other small particles in the air, called aerosols. The time between the pulse and the echo determines the distance, and the shift in the colour of the light determines the velocity of the particles along the laser's line of sight. True wind speed and direction can be calculated from these results.