Cutting edge technology

(10.03.08) Monitoring and measuring extreme weather demands extended use of high end technology. One of the crucial technologies that make the IPY-THORPEX project possible is called lidar, and can be described as the laser version of the radar.

LIDAR (Light Detection and Ranging) is an optical remote sensing technology that measures properties of scattered light. While the radar transmits radio-signals, the lidar transmits laser signals.When these light signals return to the transmitter, they may reveal information about range, speed, rotation, chemical composition and concentration of a distant target depending on the construction- in other words information important to the project.

"This technology is absolutely crucial to the project. Together with the other instrumentation in the aircraft, the lidars secure the quality and precision of the data, and thus our analyses and models", said project manager Jon Egill Kristjansson.

The prevalent method to gather information about an object, phenomenon or surface is to use laser pulses. Similar to the radar technology, which uses radio waves instead of light, data about an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal.

At the same time, the lidar technology has a special ability to reflect information on for example meteorological phenomena because of the wavelength of the signals used. Hence, the technology is used by different organizations concerned with gathering such information, for instance NASA.

In the IPY-THORPEX-project, the scientists use two different types of lidars: wind and water-vapour lidars. In combination with dropsondes and the turbulent flux probe on the Falcon aircraft, the lidars provide information about wind-speed, wind-direction, and humidity.
 
The lidars are very sensitive and gather up to 1 gigabyte of data per minute. The wind lidar operates using the Doppler effect while measuring the speed of small particles and droplets that are moved with the air.
 
The information is extremely precise: the accuracy is down to 10 cm per second of windspeed. The water vapour Lidar uses the absorption of light by water molecules at specific wavelengths.

Altogether, this provides the basis of the data in the IPY-Thorpex project.

The lidar explained: http://en.wikipedia.org/wiki/Lidar