Behind the Forecast: 5G versus accurate forecasting

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Science Behind the Forecast: 5G versus accurate forecasting

LOUISVILLE, Ky. (WAVE) - Would you trade an accurate weather forecast for the ability to scroll through social media and surf the internet on your phone faster than ever before? Soon, we may be making that choice.

In March 2019, the Federal Communications Commission (FCC) auctioned off the 24-gigahertz frequency band to wireless phone carriers in preparation for the next generation of cell phone service or 5G. The sale netted the United States $2 billion. 5G technology would make our phones more reliable and 100 times faster than on current networks. However, for this to work, there needs to be a move to radio frequencies not currently used for cell phone service. Many meteorologists and other scientists fought this decision because of the potential to unintentionally set weather forecasts back decades.

Here's the issue, these radio frequencies sold to cell phone carriers are next door to frequencies measured by weather satellites. The fear is that the new 5G transmissions would drown out necessary measurements used in vital weather models.

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So, let's break this all down step-by-step. First, what does that frequency stuff mean?

Radio waves are a type of electromagnetic energy that is represented by a spectrum that ranges from gamma rays to radio waves. Gigahertz is a unit of measurement of these frequencies of electromagnetic radiation.

Each frequency range comes with its own set of pros and cons. Higher frequencies can allow many more devices on the same network while handling faster speeds. This works by thinly slicing each range into the channel; each channel carries a limited amount of data. The wider the channels frequency band, or bandwidth, the more data it can carry. While higher frequencies, like the ones being sought out by cell phone companies, can support more devices and more bandwidth for each device, it is harder to engineer equipment for them. These radio signals don't travel as far so they fade as they travel through walls, rain and even just the air.

The FCC auctioned off two frequency groups: one between 24.25 and 24.45 gigahertz and between 24.75 and 25.25 gigahertz. Water vapor in our atmosphere emits a weak signal at the 23.8 frequency range. The lower end the frequency range auctioned off may interfere with the measurements of water vapor.

Water vapor, or humidity, data is fed into various weather models to assess severe weather potential and improve forecast accuracy. The measurements taken in the 23.8 frequency can be taken all day and night even if there is considerable cloud cover.

While water vapor absorbs and emits electromagnetic energy at 23.8 gigahertz it’s not a very strong signal. Changes in the amount of water vapor in our atmosphere makes a big difference in how much radiation is detected by satellites. Low-altitude water vapor gives off the strongest 23.8 gigahertz signal. The readings from satellites are inputted into various weather models used in weather forecasting.

The 5G band does start at 24.25 gigahertz, which is obviously different from the 23.8 gigahertz signal, but the difference is deceiving. Here’s the problem: no radio transmits at a singular frequency. Radio wave transmissions work on a swath of frequencies that peak at the target frequency. The off-target noise of 5G transmissions may bleed from the 24.25 gigahertz range into the 23.8 gigahertz range and get picked up by weather satellites. Meteorologists would be unable to tell the difference between natural and anomalous data. This inaccurate data would lead to inaccurate forecasts if inputted into weather models. A National Oceanic and Atmospheric Administration’s (NOAA) study said that satellites would lose 77% of pertinent data, setting back weather forecasts back by nearly 40 years.

NOAA’s acting chief Neil Jacobs said in June that the reduction in the accuracy of forecasts may lead coastal Americans with two to three fewer days to prepare for hurricanes and could negatively impact predictions of a tropical cyclone’s landfall.

Now, there is a compromise. Wireless phone carriers could turn down the power emitted by 5G transmitters so they don’t drown out satellite sensors. Regulators can also limit the amount of off-target noise emitted which would lessen the interference.

More actions have been planned by the FCC for the end of the year. The three additional 5G frequency bands may potentially impact other frequencies used to observe clouds, precipitation and sea ice.

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