MeteoSwiss, the Switzerland's National Weather service, is using a new system to build 3D maps of Swiss skies. This LIDAR (Light Detection and Ranging) weather measurement system has been developed at the Lausanne-based Federal Institute of Technology (EPFL). According to EPFL, this new system will be able to provide real-time maps of atmospheric humidity to the Swiss weather forecasting researchers. It can collect data continuously by shooting laser beams in the sky 30 times per second. This should help to make more accurate weather forecasts in Switzerland, a country where you can go from 4,000-meters mountains to places close to sea level in less than 200 kilometers on the ground. But read more...
You can see on the left some parts of the new LIDAR system installed in Western Switzerland's weather forecasting headquarters. (Credit: EPFL) These pictures are part of this gallery. Here are direct links to much larger versions of the top, the middle and the bottom pictures displayed on the left.
Here are some details given by EPFL about this system, which was co-funded by MeteoSwiss (54%), the Swiss Federal Institute of Technology in Lausanne, EPFL, (39%) and the Swiss National Science Foundation (7%). "The LIDAR system developed by EPFL is a relative of the familiar RADAR systems used widely in weather forecasting. Instead of sending radio waves out looking for water droplets, however, the LIDAR sends a beam of light vertically into the sky. The 'echo' here is a reflection of that light from different layers in the atmosphere. This reflection is used to build an instantaneous vertical profile of temperature and humidity. The spatial and temporal resolution is excellent – the laser beam can be shot 30 times per second, a vast improvement over weather balloons that take minutes to reach the upper atmosphere and can be sent out only a few times a day. And even though it's state-of-the-art technology, the LIDAR developed by EPFL is stable and reliable; even after a test run of several months, it did not need tuning. Traditional LIDAR systems are more finicky, typically needing to be tuned on a daily basis."
In order to shoot its beams vertically, this system needs a special installation. Here are some details provided by MeteoSwiss about this LIDAR project. "The system will be installed in a cabin, divided into two distinct rooms: a "white" room containing the system itself, with a hole in the roof allowing the Lidar beam to be sent and the backscattered light to be collected, and a computer room, from which the system will be operated." [You can see a diagram of this installation on the page mentioned just above.]
swissinfo gives us more information in this article from Simon Bradley, "Laser technology is being used to produce real-time 3D maps of atmospheric humidity" (August 27, 2008). For example, this LIDAR system "can also detect fine particles, including pollen, and from 2010 will be able to build up 3D temperature profiles."
Of course, this system has some limitations. "Unfortunately, the new system can only be used two-thirds of the time, said Bertrand Calpini, head of the MeteoSwiss Aerological Station in Payerne. 'When it's raining or snowing or with low cloud cover, the system is blind and can't work. The laser light can't get through the clouds,' he said. 'There is no way around it.'" So this system will complement other instruments already used by MeteoSwiss in its forecasting toolkit.
If you want to know how much such a system, I'm afraid it's a Swiss secret. "Officials were vague about the overall cost of the innovative project, 'SFr 750,000 for the hardware and 20 years' research work which amount to millions.' But the investment is worth it, they claim."
Sources: Ecole Polytechnique Fédérale de Lausanne, August 26, 2008; and various websites
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