All eyes have been on the possibility of C-band interference with aviation recently, but Chad Small, a Data Fellow with Grist, reminds us that questions about interference between wireless weather forecasting equipment continue today. In 2019, the FCC held Auction 102 for 2,909 licenses in the 24.25 – 24.45 GHz and 24.75 – 25.25 GHz bands.
At the time, Inside Towers reported the National Oceanic and Atmospheric Administration (NOAA) warned the FCC and Congress that 5G use in the 24 GHz band could interfere with the agency’s weather forecasting, which uses a satellite on spectrum between 23.6 and 24 GHz to detect water vapor.
“The problem is, the radio wave frequency used by wireless cellular networks is similar to the ones used to monitor atmospheric conditions,” Small recently wrote in Grist, which reports on how politics, energy, equity, culture intersect with climate. “As these two spectrum bands come under greater use, they can interfere, making the dissemination of weather and climate information slower and less accurate.”
There are plenty of differing opinions on the possibility of interference at 24 GHz. In 2019, The Hill reported then-FCC Chairman Ajit Pai’s assertion that 40,000 fixed and microwave links operate in the band just below 23.8 GHz without any reported interference issues.
Citizens Against Government Waste noted that the FCC began the process of reallocating the 24 GHz band in 2014, providing “multiple opportunities for the public and federal agencies to provide comments” before the 2019 auction. During that time, no federal agencies expressed concern until the last minute in the FCC’s public docket, the organization said.
Small, who is a Graduate Research Fellow at NOAA Center for Earth System Sciences and Remote Sensing Technologies, said 23.8 GHz is different from any other frequency. “Atmospheric water vapor – a crucial component in weather forecasting and climate modeling – primarily releases radiation in the 23.8 GHz frequency spectrum band,” he wrote. Without the ability to sense water vapor, scientists could lose their ability to provide early warnings of timing and location of landfall of deadly events such as hurricanes.
As an example of the importance of satellite-based meteorology, Small notes a 2012 hurricane forecast in Louisiana was able to pinpoint landfall of a Category 1 storm, which caused $612 million of damage.
But, currently, all eyes in the wireless industry are on building out mid-band spectrum with macro towers. When 5G will reach 24 GHz is anyone’s best guess.
By J. Sharpe Smith, Inside Towers Technology Editor
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