Multiple ground stations are being used to validate and calibrate the Aeolus satellite's Lidar sensors.
https://www.euronews.com/2018/09/21/aeolus-forecast-is-good-for-first-ever-wind-measuring-satelliteThe Andøya Space Centre is a dedicated multi-instrument atmospheric observatory 300 kilometres inside the Arctic Circle. Data gathered here will play a key role in calibrating and validating the wind measurements from space. It's a unique place.
"If you look at our location, with this observatory at 69 degrees north, there are no observatories able to take measurements together with Aeolus. So this is the one and only station doing Lidar measurements on wind velocity and wind direction at this latitude in the northern hemisphere," says the Andøya centre's Director of Science Michael Gausa.
Two telescopes from the Leibniz-Institute of Atmospheric Physics work in a similar way to the Aeolus satellite, using lasers to observe the wind. That means ESA Project Scientist Anne Grete Straume can rely on them and measurements from other ground stations for comparison throughout the Aeolus mission.
"It’s very important to understand or to check that the satellite measurements that we do are correct for all types of weather, that being storms coming in, that being good weather conditions. We need to have the comparison with these good quality ground measurements for all types of weather conditions, and this is why it’s important not to measure once and compare, but really to keep on measuring over time," she says.
Other kinds of data are also used to gauge the accuracy of Aeolus's instruments, including readings from weather balloons.
Here the team launches balloons twice a day. They gather precise local measurements of wind speed, temperature and humidity.
"With this we get in situ measurements of wind, which is very important thing in calibrating and validating the measurements from the satellite. So we can know that we’re measuring in approximately the same area. Of course the balloon will drift off with wind, but we will know that we have the same general coverage, and we can compare the measurements from the satellite and the balloon," says Staff engineer at Andøya, Ingrid Hanssen.
Aeolus is not alone - other weather satellites observe temperature and humidity and have done so for decades. However there is no global system to measure winds around our planet. We can estimate the wind from the clouds and sea surface, but not the air moving in the atmosphere.
Wind is the missing piece of the weather puzzle, as Lars Isaksen, from the European Centre for Medium Range Weather Forecasts, the ECMWF, explains:
"Some of the largest forecast errors we have had the last 5 years have been linked to our lack of understanding of the winds in the tropics. You don't have any wind information over the oceans, the southern Pacific, no wind information at all. Even in the Atlantic you have very little information about wind," he says.
All the new data from Aeolus will pass through the ECMWF to be processed and corrected against other weather data before before being passed on to forecasters.
There are so many ways this new wind data will improve forecasts. It may even fill in some of the missing information on the ENSO phenomenon and ultimatly be able to forecast the strength and duration of ENSO events.
