As major wireless networks transition to 5G, there is one “Houston we have problem” issue from my neck of the woods. The 5G networks could inadvertently degrade weather forecasts. Here’s how.
Many meteorologists like me noticed the potential problem with 5G, and now policymakers have raised their concerns. In a press release from Sen. Ron Wyden’s (D-Ore) office this week, the following statement was issued:
U.S. Sens. Ron Wyden, D-Ore., and Maria Cantwell, D-Wash., the top Democrat on the Senate Commerce Committee, yesterday warned that an ongoing sale of wireless airwaves could damage the effectiveness of U.S. weather satellites and harm forecasts and predictions relied on to protect safety, property and national security. They also released an internal U.S. Navy memo that concluded that reducing the accuracy of weather forecasts could threaten the safety of aircraft and naval vessels, and reduce military awareness of battlefield conditions. Wyden and Cantwell urged the Trump administration not to allow wireless companies to operate fifth generation (5G) communications on 24 GHz spectrum until concerns over interference with weather forecasting satellites are addressed.
What exactly is the problem? To answer this question, we have to start with a 2016 Federal Communications Commission (FCC) ruling that opened up frequencies above 24 GHz for 5G. Ok, let’s hit the pause button. What is that “frequency” and “GHz” stuff? Electromagnetic energy travels in waves and is representative of a broad spectrum from short wavelength gamma rays to longer wavelength regions such as microwaves or radio waves. (see graphic below). Gigahertz (GHz) is simply a unit of measurement of frequencies of electromagnetic radiation and is equivalent to 1 billion hertz (Hz). There is typically a flipped relationship (inverse) between the frequency of electromagnetic waves and its wavelength. In other words, higher frequency waves have shorter wavelengths.
Here’s where the problem comes in for weather forecasting. Many of the frequencies now being auctioned off for telecommunications are very close to the frequencies used by certain weather-observing satellites. So what? The “so what” is captured nicely in a recent article in Nature, a leading scientific journal. Alexandra Witze wrote on the Nature website:
23.8-gigahertz frequency, at which water vapour in the atmosphere emits a faint signal. Satellites, such as the European MetOp probes, monitor energy radiating from Earth at this frequency to assess humidity in the atmosphere below — measurements that can be taken during the day or at night, even if clouds are present. Forecasters feed these data into models to predict how storms and other weather systems will develop in the coming hours and days.
It is not only the European weather satellites that use these frequencies to probe atmospheric water vapor. The U.S. satellites do as well. The water vapor or humidity data are used to assess the potential for severe weather, and it is ingested into U.S., European, and other models to improve the accuracy of forecasts. While illusive to many, weather forecasts are made (including the one on your cellphone App) using numerical weather prediction. For a good summary, visit this link.
In a nutshell, observations from weather balloons, aircraft, satellites, and numerous ground instruments provide an initial “assessment” of the three-dimensional atmosphere. That data is fed into complex computer models solving fluid dynamics, thermodynamics, and physics equations on a rotating globe at several different levels. It is not easy folks, but the forecasts are actually pretty good. For example, a 2014 scholarly paper in the journal Monthly Weather Review reported that about 90% of data ingested into weather models are from polar-orbiting satellites. This same paper also found that without satellite data ingested into the model, the outstanding track forecasts for Hurricane Sandy would have been degraded. A significant percentage of the satellite data measures water vapor, temperature, clouds, and precipitation and relies on frequencies near the ones now available to 5G networks.
Satellite instruments use the following additional microwave-based frequencies for weather: 36-37 GHz for rainfall and snow detection, 50 GHz for atmospheric temperature, and 86-92 GHz for cloud and ice detection. All of these variables are used in global weather models. The graphic below shows global precipitation on May 15, 2019, as measured by satellites in the NASA Global Precipitation Measurement (GPM) mission. I served as Deputy Project Scientist for this mission for many years. This data is critical for weather forecasting, climate assessments, and hydrological prediction and uses some of the frequencies in question. The proliferation of these frequencies for communications may “mask” signals emitted to the satellites by water vapor, rainfall, ice or clouds. This effectively removes important information in the weather models.
5G is certainly the wave of the future, but I encourage all of the “alphabet folks” in the government (NASA, NOAA, FCC, DOD, and so on) to talk to each other. Otherwise, improvements that we have gained over the years in the weather forecasts or warnings may be DOA.