By Ellen Gray / BOISE, IDAHO/
Thursday, July 25
“It’s nice to have a flight plan to deviate from,” said DC-8 pilot Tim Vest at the debrief on Thursday night. It was just after 10 p.m. and the DC-8 had just returned from a 6-hour flight over a fire they weren’t planning on visiting.
The original plan for the afternoon was to fly to eastern Washington State, where several fires were burning in clear skies. But wildfires are tricky things. That morning during flight planning, the Shady Fire, less than 30 minutes away by air in the Salmon-Challis National Forest, didn’t look like it was going to generate an impressive smoke plume. But a half hour before take-off at 4 p.m., after the instrument teams were aboard and the DC-8’s doors were closed, the scientists staying behind to monitor the flight from the ground pulled down new satellite images.
“They said, take a look at the Shady Fire once you’re in the air,” said Carsten Warneke from the University of Colorado working at the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory in Boulder, Colorado. He’s one of FIREX-AQ‘s project scientists and was sitting in the DC-8’s cockpit jump seat as Thursday’s flight mission scientist.
Flying north on their original plan to the Washington fires, Carsten – and everyone else with an eastern-facing seat – looked out the window. Shady’s smoke plume was big and billowing. The hot and dry conditions of the late afternoon had invigorated the fire and helped to loft its smoke thousands of feet into the atmosphere.
“It was very exciting,” said Carsten. Measuring smoke was why the science team was flying. “But it was also a surprise. We had a completely different flight plan, but then there was that plume.”
So, less than half an hour after take-off, the flight plan changed.
Fortunately, the Shady Fire had been the second fire on the list for the previous day’s flight, although they’d only made one pass over its then-low-lying plume. Tim Vest and his co-pilot, Dave Fedors, both from NASA’s Armstrong Flight Research Center, were able to use the that plan once they redirected.
Flying over a wilderness area was a huge advantage. With no other air traffic, aside from a pass from a plane gathering a hotspot survey for the U.S. Forest Service, the pilots had a lot of room to work with. They guided the plane in a series of maneuvers that began with flying above the plume at 15,000 feet to gather data from the remote sensing instruments. Then they cruised to a lower altitude of about 5,000 feet above the terrain and flew through the plume in a pattern called “the lawnmower” that cut north-south back and forth across the eastward-stretching plume. By the time they’d completed the first pass, the plume had been spread by winds farther east, and the smoke gases had been reacting in the atmosphere for about two and a half hours since they began. So they went back to the source and “mowed” it again, and then did a third pass east to west through the length of the plume. By the time they headed back to Boise, the plume had extended to the Wyoming border.
Flying through the plume, it was surprisingly dark, said Carsten. During each lawnmower pass, they had zero visibility where the smoke was thickest, closer toward the Shady Fire’s vertical plume (which they didn’t fly through because it was too hot and turbulent). The light that filtered in, especially as they moved toward the less dense eastern end, was yellowish-brown that snapped to clear once they exited the smoke on each perpendicular pass.
“It was smelly, too,” said Carsten. “Not as bad as I was expecting but it still smelled like smoke.”
As mission scientist, Carsten was in charge of meeting the science goals of the flight. This largely meant he was frequently switching between chatting with the ground team who had the updating satellite imagery and two different headsets on the plane: one on the science team channel where requests for adjustments were flying thick and fast, and one on the pilot channel to figure out what was possible and safe for the aircraft. Balancing all that information, Carsten directed the details of the flight to try to get the best measurements for everyone.
“Then after we turned at the end of each pass, I would call out on the science channel ‘Get ready we’re measuring smoke in 30 seconds,'” he said.
The Shady Fire started from a lightning strike on July 10 at about 6 p.m. Since it’s in a wilderness area far from populated areas, the U.S. Forest Service has closed nearby roads and trails and is monitoring it, but otherwise letting it burn for now – with the exception of protecting specific buildings and assets in the area. So far it has burned more than 2600 acres of primarily subalpine fir and lodgepole pine trees.
For the FIREX-AQ science team the Shady Fire is exactly what they’re looking for to study smoke dynamics in the atmosphere – what are the gases and airborne particles in plumes and how do they evolve as they age and spread downwind.
“We’re measuring everything a non-chemist knows about and then 500 more chemicals,” said Carsten. The DC-8 is loaded up with instruments and more than 30 scientists to run them during flight. Among the gases they’re measuring are carbon dioxide, carbon monoxide, and nitrogen oxides, as well as particulate aerosols including soot and black carbon.
They’re also measuring chemicals formed in the plume, such as ozone. Ozone near Earth’s surface is a pollutant and health hazard that the Environmental Protection Agency monitors to evaluate air quality. It forms from a reaction of nitrogen oxides with volatile organic compounds (both emitted in large amounts from the fire) in the presence sunlight (that often forgotten ingredient in atmospheric chemistry.) During Thursday’s flight, the team saw ozone forming in the plume.
The science team’s excitement was palpable when they returned, and the instrument teams spent Friday getting a first crack at their data. Their deviation from the plan had been a huge success.
At the Friday morning briefing, when the team was taking a look at their options in Washington and Oregon for Saturday’s proposed flight, project scientist Jim Crawford from NASA Langley said, “Put together a flight plan for each of them.”
“And,” said Jack Dibb, project scientist from University of New Hampshire, “have a plan for Shady in our back-pocket.”