The Atmospheric Tomography, or ATom, mission’s world survey of the atmosphere can’t fly the order of its locations in reverse.
Its flight plan begins with traveling from California to Alaska and the North Pole before flying south down the center of the Pacific Ocean by way of Hawaii to New Zealand. From New Zealand, they cross east to Chile before ascending north up the Atlantic to Greenland.
It’s this southernmost crossing from Christchurch, New Zealand, to Punta Arenas, Chile, that’s a one-way street.
“The plane can’t make it from Punta Arenas to New Zealand because the winds are too strong,” said Róisín Commane, an atmospheric scientist at Harvard University who is part of the ATom mission.
The winds that travel from west to east above the Southern Ocean around Antarctica are among the strongest in the world. With few land masses to slow them down, they blow unimpeded.
Those strong winds led to complications for the ATom team as they were preparing for their Feb. 10 flight from Christchurch to Punta Arenas. In a small hotel conference room around a cell phone and computers sharing a screen from weather forecasters back at NASA’s Goddard Space Flight Center, Steve Wofsy, ATom’s project scientist, peered at a circular weather system at the end of their flight path. The system created an eddy in the prevailing west-east wind that coincided with their arrival in Punta Arenas. The concern around the table was that strong winds would be blowing perpendicular to the runway when the plane was trying to land, potentially pushing it sideways.
The DC-8 can handle this kind of crosswind up to about 25 knots, or 28 miles per hour. Above that, for safety the pilots would have to divert to a back-up landing site. The closest in Chile was in the range of the same weather system—and likely to have the same crosswinds. The other was in Argentina two hours away, which would require fuel reserves that would take away from the number of profiles of the atmosphere they could do on the crossing, one of the main reasons for this mission. It would also require a second flight to get the team back to Punta Arenas the day after the system passed.
It was a disruption that Wofsy didn’t want to take on after an already difficult 10-hour flight with an 8-hour time change. From their experience on ATom’s first deployment in 2016, they knew from experience that the jet lag on this leg of the trip was brutal.
After three mornings watching the updated forecasts and NASA ground personnel talking with local weather forecasters in Punta Arenas, the morning of their scheduled departure from New Zealand arrived. The forecast hadn’t changed much. There was a 20-25 percent chance that the winds would be too strong and the plane would have to divert, said Wofsy. After a last early morning meeting with the pilots and forecasters, they made the decision to scrub the flight and wait a day for the storm to pass.
By the next day the system had indeed moved on, and the runway in Chile was safe for landing. The ATom team departed after their extra day in Christchurch and with. an adjusted schedule that would give them one less day in Punta Arenas. But on a mission dependent on good weather, that’s the way the wind blows.
Good communication is key to keeping the 44 scientists and aircrew happy on NASA’s DC-8 aircraft. The team is in close quarters for a month-long journey around the world to survey the atmosphere on NASA’s Atmospheric Tomography, or ATom, mission. On the plane they keep in touch with each other via headset and with scientists supporting the mission back home via satellite chat room.
But on Feb. 6, on the other side of the International Date Line (Feb. 5 in the United States), as the team made their transit from Nadi, Fiji, to Christchurch, New Zealand, one topic was forbidden—updates on the Super Bowl.
Róisín Commane, an atmospheric scientist and Patriots fan at Harvard University in Cambridge, Massachusetts, did a rough poll. Half the people on the plane followed football, and they were nearly evenly split between Patriots and Falcons fans. And all of them wanted to see the game unspoiled.
On the ground in Christchurch, Quincy Allison, the logistics coordinator with NASA’s Earth Science Project Office out of Ames Research Center, had already arranged with hotel staff to record the game and play it in a conference room after the ATom team got in that evening.
Meanwhile, during their Super Bowl news blackout, the team continued to make measurements to better understand our atmosphere. The ATom mission is the most comprehensive survey of the atmosphere to date, with 22 science instruments measuring more than 200 gases and air particles and an itinerary that has it tracing from the North Pole down the Pacific Ocean to Christchurch, then cutting across to the southern tip of Chile, then traveling back up the center of the Atlantic to Greenland and the Arctic. Along the way they’re island hopping between flights, with only a day or two on the ground before moving on. Christchurch, at about halfway, is their longest stopover at three days and also their major resupply point.
Gathering data to help understand the atmospheric chemistry that drives air quality around the globe is worth the grueling pace for Commane, who likened the atmosphere to a different kind of bowl.
“It’s like a mixing bowl,” she said. The air over the oceans is theoretically clean, but winds, especially in the Northern Hemisphere, carry pollution from industry or fires from continent to continent. Looking at some of their data in the middle of the Pacific Ocean, she said they saw signs of fires. “I said, ‘Where did this come from?’” she recalled. The weather and wind models said Africa, where agricultural fires are common in the summer and fall. “That’s on the opposite side of the world.”
Air doesn’t stay in one place, and as it travels, the hundreds of different gases and particles that make up the air encounter new ones generated in different areas, and they chemically react with each other. Some of the pollutants are scrubbed out of the atmosphere this way, disappearing or transformed into new gases. These are the processes that the ATom science team is interested in learning more about, in addition to just knowing how much pollution is really out there over the ocean.
A lack of measurements gives people a false sense that everything is okay, said Commane. “We think we don’t need to do better,” she said. Poor air quality is something she doesn’t want anyone to live with, whether it’s generated at home or is a wind-driven import. “You might not always be able to see it, but when you’re in it you can feel it. You can taste it.”
It was a week of eclectic locales last week for the Atmospheric Tomography, or ATom, mission. On Monday, August 1, NASA’s DC-8 flying laboratory took off from the high desert of NASA’s Armstrong Flight Research Center in Palmdale, Calif., and made its way to near the North Pole before touching down in Anchorage, Alaska. Two days later, the team left the cool, crisp air for balmy Hawaii, laying over for a few days in Kona, on Hawaii Island.
All the while, in flight the 23 instruments on board measured and collected air samples from a range of altitudes as part of the mission to survey the world’s atmosphere.
Upon liftoff from Palmdale, the team caught glimpses of two defining features of the summer Southern California air: haze from smog stemming from the Los Angeles Basin, and smoke and ash from a wildfire, this one from the tail end of a large blaze that charred about 65 square miles (39,000 acres) in the mountains near Santa Clarita Valley.
“More frequent wildfires in this area are expected because of climate warming,” said ATom principal investigator Steve Wofsy, noting that drier landscapes and higher temperatures up the odds of igniting a blaze.
The crew also sighted wildfires in areas near Pyramid Lake, in northwest Nevada, that had been started by dry lightning strikes a few days prior.
But eventually the air cleared as the DC-8 soared over the dramatic vistas of the northwest United States before continuing on to the Arctic, which Wofsy called “the heartland” for climate change.
“The Arctic is changing very, very quickly, and we wanted to see how it’s changing both in terms of its climate and its atmospheric chemistry,” he said. The Arctic is warming faster than the rest of Earth. Temperatures in the region are now 2.3 degrees Fahrenheit above the long-term average, the highest since modern records began in 1900.
ATom scientist Roisin Commane of Harvard University noticed one of the most visible markers of that warming—the skinniness of the first-year sea ice compared to years past. “Even way up at 78 degrees north latitude, the sea ice was really, really thin,” she noted. “Twenty years ago, there would have been thick and lumpy sea ice all over.”
Another observation taken from instruments were heightened amounts of sulfur aerosols. “Normally the sea ice would keep a lot of the chemical compounds sealed in,” Commane said, “but with so much broken ice, everything can make its way out pretty easily.”
“Aerosols often have a cooling effect on the climate because they scatter sunlight and make clouds whiter and last longer,” added Christina Williamson, a post-doctoral scientist at the Cooperative Institute for Research in Environmental Sciences at the University of Colorado at Boulder. “In the Arctic this may not happen because snow and ice are already highly reflective, but with less and less sea ice, they could become more important.”
At high altitudes, the team picked up gases indicative of biomass burning, which scientists on board suspect came from recent wildfires in Siberia. Wherever they came from, the gases originated very far away since they were picked up in a remote area of the Arctic.
In fact, many gases are world travelers. On Wednesday, August 3, on the way to Kona, the DC-8 flew through a highly polluted layer of atmosphere a couple hundred miles north of the Hawaiian islands. It likely came from Asia, says Paul Newman, Chief Scientist for Earth sciences at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and co-leader of the ATom science team. “The pollution was probably lifted to higher altitudes by convection in Asia, and then carried over the Pacific by the normal westerly winds.”
This around-the-world trip has only just begun, but it’s already proving to be interesting. “It’s exciting just seeing what comes in,” Commane says. “We’re never sure what to expect.”
by Samson Reiny / OVER THE EQUATORIAL PACIFIC OCEAN /
Feeling breakfast move toward my chest is the uneasy cue that NASA’s DC-8 flying laboratory is dropping altitude. We drop all right, from 35,000 feet to just 500 feet above the open ocean — the water so close the airplane’s wing starts to look like a diving board.
Suddenly, the plane climbs hard, zooming toward the clouds. Standing, my feet are glued to the floor, the rest of my body wanting to follow. I’m dizzy, but I eventually adjust as we ascend to higher elevation.
That is, until we dive again. Seven more times, to be exact.
“I’ve never had such a nice flight,” says Donald Blake, smirking. An atmospheric scientist at the University of California, Irvine, he has flown on the DC-8 countless times over the years. “One of my students threw up 19 times during a really bad flight over Central California. I told him, ‘You’re never flying on this thing again.’ Well, I barely managed not to throw up myself.”
But in retrospect motion sickness is a small price to pay to accomplish the Atmospheric Tomography (ATom) mission’s ambitious objective: to survey the atmosphere around the world at a range of altitudes (hence the dramatic dips and ascents). The 23 instruments on board are tasked with measuring all together more than 200 gases and airborne particles in the most remote regions on Earth in order to help advance a number of scientific investigations.
On Friday, July 29, I joined 30 researchers on their first science flight: a nine-hour trek from NASA’s Armstrong Flight Research Center in Palmdale, Calif., to the equator in the Pacific Ocean and back. Next up would be a 23-day whirlwind trip, with far-flung stopovers in American Samoa in the Pacific, Ascension Island in the middle of the Atlantic, and Kangerlussuaq, Greenland, in the Arctic Circle, among others.
What is clear about being on a science flight is that instruments are the first-class passengers. These costly, often oven-sized machines are checked incessantly, the thermostat set to their liking, their bodies secured for the vicissitudes of flight. From the onset, they cause a ruckus, some more than others. At one point, a distressed passenger snatches my front row seat while I’m away. She points first to her ears then to the back of the plane. I hear a high-pitched warble that becomes more shrill the closer I move toward it.
“I should have told her the instrument behind me gets particularly loud,” says a regretful Roisin Commane, an Irish-born Harvard University scientist who’s assisting with the Quantum Cascade Laser, or QCLS, which uses light absorption to measure levels of carbon dioxide, methane, carbon monoxide, and nitrous oxide.
If all is well, Roisin’s instrument pretty much runs on its own, making her one of the lucky ones. Others are married to theirs. University of New Hampshire scientist Jack Dibb, a gruff, ponytailed man, is always on his feet changing out filters for his Soluble Acidic Gases and Aerosols, or SAGA, instrument as it passes through a string of altitudes and latitudes. The filters will be brought back to a lab and analyzed for pollutants such as nitric acid and for aerosols that are signatures of biomass burning, which includes wildfires.
Donald Blake, the veteran DC-8 traveler, usually has his hands full fussing with the valves of his Whole Air Sampling machine, capturing air samples in cans to be sent to his and others’ labs for analysis of a hundred different gases and particles. Today fellow UC Irvine researcher Barbara Barletta is helping out. The duo eventually fills 166 cans.
Some instruments even require their own maneuvers. The Meteorological Measurement System records in situ pressure, wind and temperature data. To establish a reference point for the wind measurements, the DC-8 pilots conduct a few maneuvers, namely the “pitch” (quick up-and-down movements), the “yaw” (moving side to side like a crab), and the “box” (a succession of tight turns that result in a box pattern when seen from above).
Even in the cockpit, the safest spot for a sensitive stomach, these maneuvers make me squirm. “Nobody likes that guy,” Blake later says jokingly of the instrument’s scientist.
Throughout it all, many researchers are hunched over computers, transfixed by the incoming data displayed through colorful graphs and charts. Over the intercom, they share results, talking in science jargon, and communicate with the navigator and the mission director and assistant mission director, who negotiate the science team’s needs with the pilots.
As we near the equator, when I hear Tom Ryerson, who leads a research group in the National Oceanographic and Atmospheric Administration’s Chemical Sciences Division, exclaim over the intercom, “This is lowest NOy [total reactive nitrogen] measurement I’ve ever seen, 70 ppt [parts per trillion],” I take notice.
NOy, Ryerson explains, is the sum of all nitrogen oxides, which derive from pollutants emitted from power plants, cars and trucks, and forest fires. His Nitrogen Oxides and Ozone instrument is delivering that measurement in real time. Levels of NOy are usually lower near the southern hemisphere, far away from their sources, but not this low, he says. “This was really low—about 10 times lower than in the northern hemispheric air we just sampled on our way south from Palmdale.”
NOy measurements taken during the rest of the mission will be useful for testing global models that simulate sources of NOy on the continents and how they’re mixed around between the northern and southern hemispheres and also how they’re scrubbed by clouds.
“The key thing about ATom is that we’re making these measurements in very under-measured parts of the world where the global models have very few measurements to compare against,” Ryerson says. “We’ll measure some things in some parts of the world that really haven’t been observed before.”
Moments later, he informs me that a few of the instruments picked up dust particles the team think came from Africa. Their sizes are much larger than expected and may indicate something new about how far dust can travel after being picked up by windstorms in the world’s deserts.
“Not bad at all for a first flight,” Ryerson says. “It feels like the start of a concert. The instruments are warming up, right before the symphony starts. There’s lots of anticipation of great stuff to come.”