Don't be alarmed if you stumble on this antenna array in the Anchorage woods

A weather radar that can measure wind speed and direction at different levels in the atmosphere was under construction last week on a knoll on the Campbell Tract in East Anchorage, but it's mainly designed to forecast the paths of volcanic ash plumes that could cause problems for airplanes.

The radar, owned and operated by the National Weather Service, points directly skyward on a 6-foot-tall rectangular platform. It was being built on a clearing in forested land owned by the Bureau of Land Management, not far from the Campbell Airstrip.

Three similar radars have operated in Alaska since 1999, in Talkeetna, Glennallen and the Yukon village of Central. But those devices are aging and becoming more difficult to maintain, said Christina Horvat, engineering branch chief at the National Weather Service's Radar Operations Center in Norman, Oklahoma.

Through an $8.4 million replacement project, the Talkeetna radar is staying put. The other two new radars are being built in Anchorage and Homer. The Homer radar is near completion, Horvat said. 

It's a breath of new life into a mostly defunct federal "wind-profiling" network that was largely concentrated in the Midwest in the 1990s. While the technology is largely considered obsolete in the United States, it has still been useful in Alaska for its ability to forecast movement of volcanic ash, said Horvat, who is coordinating the project from Oklahoma.

"Budgetary restrictions, at present, afforded only the opportunity to refresh in Alaska," Horvat said.

Weather and climate scientists have used the radars, known as wind profilers, to study the ionosphere in the Earth's upper atmosphere. The radar array uses electromagnetic signals to remotely sense wind speed and direction, according to the National Weather Service. The antennas emit pulses that bounce off the upper atmosphere and indicate the turbulence of wind patterns when they reflect back to Earth.

Up to 35 of the devices operated in the United States for more than two decades, mostly in the middle of the country. Officials have credited the radars for saving numerous lives in 1999 when a tornado outbreak hit Oklahoma City.

The technology has since shifted to wind balloons and sensors on airplanes. But in Alaska, the wind profilers are still used to forecast the direction of volcanic plumes, which affect flight patterns and can have serious consequences. A KLM passenger jet flew through an ash plume from Redoubt Volcano in 1989 and lost all four engines. In a cockpit and cabin darkened with ash, the pilots were able to restart the engines in time for an emergency landing in Anchorage, but the engines were destroyed, the hydraulics were ruined and the plane was stripped of its paint.

Data from the wind radar is generated every six minutes, with the sensors measuring the atmosphere to about 10 miles above the radar, which lies horizontally and directly faces the sky.

Construction workers were at the site last week, and the installation didn't go unnoticed by passers-by. Jim Cocallas biked past the construction site on his bike a few weeks ago.

Cocallas has been trying to find out more about it since. He said he lives in a nearby neighborhood and was concerned he hadn't received public notice of the project. 

Maureen Clark, a spokeswoman for the BLM, said her agency released a public notice in December 2015. A 17-day comment period was held in July 2016, Clark said. She said the agency received no comments.

Acknowledging possible neighborhood concerns, Horvat, of the Radar Operations Center, described the radar as "very low-powered" and quiet. She referenced a 2009 electromagnetic energy assessment that found the energy emitted by the wind profilers to be within health limits set by the Federal Communications Commission.

An environmental analysis conducted by the Bureau of Land Management described the purpose and need for the radar this way: "To support forecasting and warning operations information for the protection of life and property in Alaska as it continues to be on the leading edge of climate change."

But Horvat, who works for NOAA, said the radar has nothing to do with climate change investigations. She said she wasn't sure why the BLM decided to include that sentence in its 2015 analysis.

"My particular facility, at this time, is not looking at that," Horvat said. "We're looking at responsibility for operations and maintenance."

The new Talkeetna wind profiler has already been completed. Horvat said she expects the Homer and Anchorage radars to be completed by the middle of August. Each costs about $333,000 annually to maintain, according to Horvat.

The old profilers in Central and Glennallen will keep operating for about a month to compare data before being removed, Horvat said.

Correction: This article has been edited to reflect that a 17-day comment period was held in July 2016, not a three-day period.