By Kerry Taylor-Smith
Forecasting the weather is a tricky business – its hard to be completely accurate with predictions although continuous improvements in how the heavens are monitored is making this job somewhat easier.
Predicting Weather by Studying Wind Behavior Using Different Satellites
Aeolus, a weather satellite launched from French Guyana in August 2018, aims to impact the quality of medium-range weather forecasts – those that predict the weather for the coming few days - by keeping a close eye on the wind from space. Named after Aeolus, the keeper or guardian of the winds in Greek mythology, the satellite will gather data with the purpose of providing a full picture of the behavior of the wind all over the planet to help improve daily weather forecasting and predict extreme weather.
The British-assembled satellite forms part of the world’s first space mission to map the Earth’s winds on a global scale and sits 320 km (200 miles) above the planet. It will follow a dawn/dusk orbit – so it shadows the borderline between day and night on Earth, which ensures its solar panels always receive the same amount of energy from the sun. It employs a single instrument; a Doppler wind LIDAR and telescope named Aladin. This advanced laser system is the first to use an ultraviolet laser to measure weather from space and relies on the Doppler effect, which observes the change in frequency of sound, light, or other waves as the source and observer move towards or away from each other. It has been designed to accurately traces the movements of air particles from space to augment climate research and weather forecasting, particularly in the tropics where data is lacking.
Aladin transmits short but powerful pulses of ultraviolet laser light through the atmosphere towards the Earth: on its journey, some of the light hits particles – moisture, dust and gases – moving around in the air/wind at different altitudes and scatters some of this back towards a transceiver where it is collected and recorded. The delay between the outward pulse and inward signal provided data on the direction and speed of the wind, and how far it has traveled. The information is then downloaded daily to a ground station in Svalbard, Norway and from this data, meteorologists are able to adjust their numerical models to match the data from the satellite, allowing them to improve the accuracy of forecasts.
Significance of Studying Wind Behavior
But why is this important? Aeolus will map the wind across the globe, but particularly the tropical winds. The tropics receive most of the sun’s energy and are often where large-scale patterns of circulation in the atmosphere are triggered. However, the tropics are a data blind spot where the behavior of winds are poorly mapped because of an almost complete lack of direct observations. Bad storms in Europe for example, sometimes originate in the tropics, and often their severity can be underestimated because initial-state conditions fed into models don’t have the most accurate wind information. It is important to get the conditions in the tropics correct in the initial stages to forecast the mid-latitudes appropriately in the medium range.
Aeolus is only a demonstration mission; it will spend three years probing the lower levels of the atmosphere to study wind patterns on a global scale. Within the first year of testing, the satellite’s routine forecasting should be including the laser’s information. It is hoped that this mission could provide useful data for future operational weather satellites designed to employ lasers. But this will not be up to European Space Agency – who are leading this mission – to build future satellites; that is for operators of weather satellites and weather programs to achieve.
References and Further Reading