LiDAR and radar have become widely accessible sensing tools for creating 3D representations and designs. Recently, a new method of remotely measuring wind speed has been developed, potentially opening up new possibilities for the use of sensing technology. Despite significant progress in data collection and assimilation, measuring air mass movement still poses a challenge. Traditional contact methods are still typically employed today, such as the use of sensors installed on weather stations or sounding balloons.
“Information on atmospheric dynamics is still fairly hard to obtain through direct observations. As of today, the most reliable way to remotely measure wind speeds is using Doppler radar. This technique involves sounding the environment with a powerful source of radiation and therefore takes considerable resources, including power, equipment mass, size, and cost,” says Alexander Rodin of the Applied Infrared Spectroscopy Lab at Moscow Institute of Physics and Technology (MIPT).
Weather radars can only measure distance within a range of tens of thousands of meters and are often unreliable beyond the troposphere. Direct measurements using satellites have been tried but only a few were able to successfully measure air mass movement. LiDAR, on the other hand, is only highly effective at local distances of a hundred meters or less.
Physicists from MIPT developed a new instrument that uses an RF engineering technique called heterodyne detection. This involves multiplying a signal with a local oscillator to shift it to an intermediate frequency. MIPT’s heterodyne spectroradiometer mixes the received signal—solar radiation that has passed through the atmosphere—with the local oscillator, a tunable diode laser.
The main challenge when using heterodyne detection is to maintain the local oscillator’s exact frequency. Exceeding even just 1MHz can render the entire operation useless. This resulted in a deeper study of diode laser emissions. The heterodyne spectroradiometer has ultra-high spectral resolution which allows it to measure infrared atmospheric absorption spectra. It can successfully detect and measure wind speeds with an accuracy of 3 to 5 meters per second. Overall, the spectroradiometer can detect wind profiles of up to 50,000 meters (30 miles).
“We decided not to use machine learning but to implement a classical approach based on Tikhonov regularization. Despite the fact that this method is known for more than half a century, and it is widely used all over the world, its capabilities are far from being exhausted," says Rodin.
MIPT will be using the new device in an observational campaign to measure the stratosphere polar vortex and greenhouse gas concentration in the Russian Arctic. The team is hoping that this new development will “create extensive networks for atmospheric monitoring.”
The research is published in Atmospheric Measurement Techniques. Read the complete study here.
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