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In August 2018, British-built satellite Aeolus launched from French Guyana, tasked with keeping a close eye on the wind from space.
The hope is that by tracing the movement of air particles, Aeolus – so-called after the guardian or keeper of the wind in Greek mythology – will help improve the quality of medium-range weather forecasts, those that predict the conditions for the coming few days.
Challenges Involved in Weather Forecasting
Making accurate predictions about the weather isn’t easy – remember Michael Fish stating there was no hurricane on the way in 1987, which was followed by the worst storm to hit South East England for 300 years. But it is getting easier thanks to the continuous improvements being made in how the firmaments are being monitored.
Residing 200 miles above the planet, the British-assembled satellite is part of the world’s first space mission to plot the Earth’s winds on a global scale. Data on the winds has never really been collected before - representing a huge gap in the global observation system – and it is hoped that Aeolus will provide around 64,000 wind profiles a day. It will gather data across the entire Earth – from the ground up to the stratosphere - to provide a full picture of the behavior of the wind globally to not only improve daily weather forecasting but predict extreme weather too. It might also have a role to play in improving air quality models that are used to predict dust and other airborne particles that might affect public health.
Aladin – A Doppler Wind LIDAR and Telescope
Aeolus has just one instrument – Aladin, a Doppler wind LIDAR and telescope designed to accurately measure global wind patterns in space. This sophisticated laser system relies on the Doppler effect, which perceives the change in frequency of sound, light, or other waves as the source and observer move closer or further away from each other.
Aladin is the first instrument to utilize an ultraviolet laser to accurately trace the movements of air particles from space. It sends short, powerful pulses of light towards the Earth; as it travels through the atmosphere, some of the laser light will hit particles of moisture, dust and gases which are moving about in the air/wind at different altitudes. This light is scattered back towards a transceiver to be collected and chronicled. The delay between the outward pulse and inward signal offers information on the direction and velocity of the wind, as well as the distance it has traveled. The data is downloaded on a daily basis to a ground station in Svalbard, Norway, allowing meteorologists to alter their numerical models to match the data from the satellite and improve the accuracy of forecasts.
Improved Climate Research and Weather Forecasting
By measuring the weather from space, Aladin will boost climate research and weather forecasting, especially in the tropics where data is lacking. Most of the sun’s energy is concentrated in the tropics, which is often where large-scale patterns of circulation in the atmosphere are generated. But the tropics are a data blind spot; an almost complete lack of direct observations means the behavior of winds are poorly charted. Severe storms in Europe for example, can originate in the tropics, but their brutality if often underestimated because inaccurate wind information is fed into initial-state condition models. It is imperative to ensure the conditions in the tropics are correct in the early stages to predict the mid-latitudes correctly in the medium range.
Conclusion
Aeolus serves simply as a demonstration, and it has been given only three years to analyze lower levels of the atmosphere to study wind patterns on a global scale. The satellite will begin a testing phase and should include routine forecasting including the laser’s information with in the first year. This mission could provide useful data and pave the way for future operational weather satellites designed to employ lasers. But the European Space Agency – who are leading this mission – will not be building future satellites; that task will be for operators of weather satellites and weather programs to achieve.
References and Further Reading
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