Will 5G mobile networks wreck weather forecasting? DW.com
Meteorologists were able to forecast Storm Sabine well before it hit Germany. But they will have it harder when 5G networks spread. The new mobile phone frequencies disrupt weather satellites. Click To Tweet
Weather forecasting has never been as precise as it is today. That’s thanks in large part to Earth observation satellites, which record and deliver a variety of exact weather data. That data then gets fed into computer models to generate weather reports.
One of those data is the level of water vapor in the atmosphere — that’s water that evaporates and turns into steam, making it practically invisible. When that steam (a gas) cools, we get clouds.
Satellites run by the European Space Agency (ESA) and its American counterpart, NASA, monitor such developments. They make the process visible. And that's extremely important for meteorologists. Click To Tweet
The better the data, the better meteorologists can forecast storms, hurricanes, typhoons and cyclones and when and where those weather events will make landfall. But if they don’t have good data, those predictions can be wrong by hundreds of kilometers.
The intrinsic radiation of steam molecules
Weather satellites measure atmospheric steam, or water vapor, using passive sensors. Those sensors can detect very weak, microwave signals in a spectral band between 23.6 and 24 gigahertz (GHz). Click To Tweet
“The radiation is caused by the smallest changes in the speed at which water molecules rotate,” says Dr. Clemens Simmer, a professor of meteorology at the University of Bonn,
“And we measure water vapor at 22.235 GHz, where other gases and even clouds have practically no effect. So, we’re only measuring the water vapor. The emission is nothing more than heat radiation, the same as in a kitchen stove — except we’re measuring it in a different spectral range.”
The problem is that the International Telecommunication Union (ITU) decided at its 2019 world conference (WRC-19) in Sharm el-Sheikh, Egypt, that the new 5G mobile network should operate in the range of 24.25 and 27.5 GHz.
That leaves a slim 0.25 GHz of separation between 5G mobile telecommunications and that all-important water vapor range that meteorologists need to predict storms. It’s almost inevitable that 5G — its send-and-receive masts and our mobile devices — will disrupt the flow of weather data to meteorologists.
“The emissions don’t just stop at 24 GHz because every transmitting device has a certain range,” says Simmer. “It’s unavoidable with some bandwidths. There will be interference.”
Add to that the fact that the emissions from water vapor are very weak.
“They are very low changes in the levels of energy of the water molecules and that’s what makes this so difficult, because the smallest interference can wreck the signal,” Simmer adds. “So, we need very low thresholds for transmitters that emit signals below the 24 GHz.”
Tiny transmitter — big effect
Today’s weather satellites have a surface range-resolution of between 10 and 30 kilometers (6.2 and 18 miles). That means that a cell tower or mobile devices that stray into a weather satellite’s frequency range could disrupt its readings for a larger area.
To begin with, that could be a big problem for urban centers and residential areas. But as there are plans to use 5G to support autonomous driving, the problem could soon also affect long-distance routes and freeways. And that won’t be the end of it.
“5G will most certainly get implemented on ships and airplanes,” says Simmer. “We’ll get these same interferences all over the world.”