Visible satellite image on March 23, 2019. Image: CIRA/RAMMB

A struggle is brewing between the nation's weather and climate agencies and the wireless industry concerning 5G spectrum and the reliability of our weather forecasts.

Why it matters: The tug-of-war over a key swath of airwaves underscores the increasingly intense battle for coveted airwaves that power not only our smart phones but also other equipment critical for public safety, including weather forecasting.

  • Radio spectrum, a finite resource, will only become more scarce and sought after as demand for wireless technologies continues to explode.

The gritty details: In March, the FCC began auctioning off spectrum in the 24 gigahertz (GHz) band of radio frequencies, which are high-frequency microwave licenses to be used in delivering the 5G services all the nation's carriers are vying to deploy. (AT&T, T-Mobile and Cox were among the pre-approved bidders.)

  • These 24 GHz license are appealing to national carriers because they include more densely populated areas, where carriers are desperate to add capacity for mobile broadband to keep up with exploding demand.
  • In 2014, the FCC sought feedback from other agencies and airwave users about the plan to sell off the 24 GHZ spectrum for 5G. In 2017, FCC engineers set the baseline interference limits — in other words, limits on the amount of "noise" devices are allowed to emit without interfering with neighboring users.

The problem: These auctioned airwaves are near those used by NOAA equipment, including specialized sensors, designed to see through the clouds to understand what is happening inside weather systems. These sensors operate at a frequency of 23.8 gigahertz.

"Microwave satellite data is the weather-equivalent of a medical CAT scan," says Jordan Gerth, a meteorologist at the University of Wisconsin at Madison.

  • Right before the auction began, NOAA and NASA sounded alarms that using the 24 GHz airwaves for 5G purposes could cause substantial interference with weather-forecasting sensors and hinder the ability to predict severe weather, and could even hamper typical 7-day forecasts.
  • On May 16, acting NOAA administrator Neil Jacobs told Congress that NOAA and NASA concluded the emissions limit advanced by the FCC would result in about 77% data loss from passive microwave sounders.
  • "If you look back in time to see when our forecast skill was roughly 30% less than it was today, it's somewhere around 1980," Jacobs said.
  • The House Committee on Science, Space and Technology asked the FCC to delay the auction the day before it was scheduled to begin.

The intrigue: The situation escalated politically and White House officials, having made 5G build-out a priority, sided with the FCC.

  • FCC Chairman Pai pushed back: “The Commission’s decisions with respect to spectrum have been and will continue to be based on sound science rather than exaggerated and unverified last-minute assertions.”
  • The auction moved forward, with bids grossing nearly $2 billion.
  • But NOAA and NASA warnings over the interference concerns have grown louder. A Commerce Department official overseeing spectrum issues ended up leaving the job amid the inter-agency fight.

This week, the wireless industry's main lobbying group CTIA torched the Commerce Department for using what it says are false interference claims to undermine the Trump administration's 5G strategy, and for not following protocol to voice concerns earlier in the 5-year auction planning process.

  • "Their proof is based on protecting a sensor that was never deployed," CTIA's Brad Gillen wrote in a blog post.

Meteorologists disagree. "If 5G networks are deployed under the terms of the sale, this is a legitimate threat to forecast quality," Gerth says.

  • "Our frequency allocations are based on the properties of molecules; we cannot sense somewhere else," he says.
  • The FCC and Commerce Department declined to comment. NOAA and NASA did not respond to requests for comment.

What's next: This fall, the World Radiocommunication Conference meets in Egypt to set global agreements around radio frequencies for 5G. FCC officials fear having a disjointed position on the airwaves will undercut its leverage in negotiating standards with other countries.

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