This desert was nothing like what I expected. Flying in to Walvis Bay Airport in Namibia, Africa, unbroken beige stretched as far as I could see out the window, lined with the occasional road and dotted by the occasional black rock outcrop, like islands in the sea.
From the ground at first glance, it’s pretty boring in most directions: big sky and flat sand with little to interrupt the horizon. Until you turn and see what look like orange-ish mountains in the distance. They’re not mountains. They’re dunes. As we drive closer, they keep getting bigger. The Crocodile Dundee voice in my head says “Now, that’s a dune.”
The dunes are the most spectacular feature of the Namib Desert, one of the oldest deserts in the world, that runs the length of the Namibian coast on the western shore of Africa. But it’s the coast – specifically the clouds above the Atlantic Ocean to the west – that have brought a team of NASA and university scientists and two research aircraft to this remote region for a NASA airborne mission: Observation of Aerosols above Clouds and their Interactions (ORACLES).
Offshore are two things that make the coast of Namibia unique in the entire world: a layer of low-lying cumulus clouds and above that a steady layer of smoke particles – a type of aerosol – that are borne westward on the winds from forest and brush fires over central Africa.
Aerosols and how they change the behavior of clouds are one of the biggest mysteries in the climate change puzzle. Do aerosols make clouds thicker? Do they reflect more sunlight, or change how much sunlight clouds reflect? Do they absorb sunlight and make the atmosphere warmer? The lessons learned from flying above and through this “perfect natural laboratory,” as principal investigator Jens Redemann put it, will yield insights into cloud-aerosol interactions around the world.
The same conditions that make the low-lying clouds also make the coast really foggy in the morning. The fog is a reliable source of moisture for the plants that cover rocks and boulders sticking out of the sand. Desert-warmed air condenses over cold ocean water to form a marine layer, similar to the ones seen on the California coast.
We are staying in Swakopmund, a tourist town about 45 minutes from the more industrial city of Walvis Bay. This is a former German colony town founded in 1892, and you can see the influence on the architecture. The town is built out rather than up. A constant breeze blows keeping the late August air a nice 70 to 75 degrees Fahrenheit.
As we drive south toward the airport on our first full day here, we’re between two extremes with the Atlantic ocean out the right window and the desert out the left.
The ocean is blue and huge, and vacation rentals dominate a long section of beach, giving way to a view of offshore drilling platforms in the distance as we near the city of Walvis Bay. Like Swakopmund, the city is spread out, and signs on the highway caution to watch out for children crossing between two residential areas.
At the southern reach of the city new construction is going up as we turn inland toward the desert and the airport. The dunes in the distance grow until we pass Dune 7, the tallest in the area at over 1200 feet. Out here, under the sun, the temperature will be in the 90s F by midday.
Soon after we arrive at Walvis Bay Airport, a tiny bump on the horizon that will be the ORACLES base of operations for the next month. A spill of scientists, freshly badged for airport access, disembark out of the shuttle van, ready to go.
For the next month Earth Expeditions lives up to its name as we wrap up our reporting on NASA scientists in the field by taking you to three far-flung locations around the world. Our final trio of 2016 expeditions is exploring the edges of the Greenland ice sheet, potential climate changes in clouds off the Atlantic coast of Africa, and the condition of the Great Barrier Reef in Australia.
Our reporting team has just arrived in Walvis Bay, Namibia, for the start of the ORACLES airborne campaign looking into the complex interactions of tiny aerosol particles and clouds and their impact on climate. Two NASA aircraft are now at Walvis Bay for the mission, which will continue through the end of September. Our team begins blogging right here tomorrow!
Where there’s smoke there’s fire, but what if there are also cloud condensation nuclei? Clouds help to keep the planet cool by reflecting sunlight back into space. Aerosols such as smoke particles contribute by mixing with water vapor, resulting in “cloud seeds” that, in addition to forming raindrops, create brighter and more reflective clouds. On the flipside, smoke particles can absorb sunlight and contribute to atmospheric warming.
The ORACLES (Observations of Aerosols above Clouds and Their Interactions) campaign takes to the skies of the southern Atlantic to investigate this cloud-aerosol phenomena. “Aerosols work as a sort of a sun-umbrella,” said ORACLES principal investigator Jens Redemann. “Whether they’re absorbing or not, they have implications for clouds and cloud formations.”
In mid-September another NASA reporting team will be traveling with the Coral Reef Airborne Laboratory (CORAL) mission to the land down under to probe portions of the Great Barrier Reef. CORAL is looking at the interplay of factors that influence these complex underwater ecosystems.
To date coral reefs have primarily been studied with scuba gear and a tape measure as the dominant tools of the trade. But CORAL will investigate reefs en masse with the use of an airborne instrument to record the spectra of light reflected upward from the ocean. Those measurements allow researchers to pick out the unique spectral signatures of living corals, sand and algae as well as create ecosystem-scale models of reef conditions.
The Earth Expeditions team will be reporting from Cairns, North Queensland – the gateway to the Great Barrier Reef – and Heron and Lizard Islands. CORAL will sample six sections across the length of the reef, from the Capricorn-Bunker Group in the south to the Torres Strait in the north.
“CORAL is a unique opportunity to obtain a large uniform data set across several reef systems. This will give us a whole new perspective on coral reefs,” said Eric Hochberg, CORAL principal investigator. Future field work of the three-year field campaign will inspect coral reefs in Hawaii and the Micronesian islands of Palau and the Mariana Islands.
On the opposite side of the globe from Australia, the Oceans Melting Greenland (OMG) campaign will be dropping some 250 probes from a NASA aircraft into the waters on Greenland’s continental shelf and in its fjords. The probes measure ocean temperature and salinity as they sink thousands of feet into the water, transmitting the data to the aircraft above. Combined with OMG’s new maps of the seafloor along the coast, the probe data will show where warm, subsurface waters can come in contact with the undersides of glaciers and melt them from below.
The rate of underwater melting in Greenland has been one of the greatest uncertainties in predicting future sea level rise, according to Josh Willis, OMG’s principal investigator. With the intensive measurements that OMG will gather in its five-year span, “We may not solve the problem of predicting sea level rise, but we hope to make a dent,” he said.
To reach all of Greenland’s coastline — which is eight times the length of the U.S. East and West coasts combined — the OMG team will use four different bases in Greenland, Iceland and Norway between mid-September and early October. Our Earth Expeditions reporting team will document OMG’s work as winter approaches in the Far North.
At first glance, it looks like a typical, picture-perfect lake. But scan the reeds along the shore of this pool on the outskirts of Fairbanks, or glance at the spruce trees lining the banks, and you notice something different is going on.
Bubbles. There are bubbles popping up among the reeds, like bubbles from a fish tank aerator. A couple clusters, steady streams of small half-circles, vent near the shore. Then another group appears in deeper water.
And the trees. Some of them are not growing in the directions trees normally do. They stick out drunkenly over the lake, then take a turn upwards at the top.
The explanation for both of these features is in the soil. Permafrost—soil that remains frozen year-round—lies underneath the moss, needles and topsoil of the site. As that permafrost thaws, the ground above it can sink, knocking trees askew and forming pools of water called thermokarst lakes.
“The carbon locked in permafrost for thousands of years is released to the lake bottom,” said Prajna Lindgren, a postdoctoral researcher at the University of Alaska, Fairbanks, Geophysical Institute.
These lake beds, she explained, provide a perfect environment for microbes to eat up the carbon released from the thawing permafrost. This produces methane—a potent greenhouse gas that is released in bubble seeps. As part of the NASA-funded Arctic Boreal Vulnerability Experiment, or ABoVE, Lindgren and her colleagues are studying these seeps and mapping how thawing permafrost is affecting the changing lake edges.
“We’re trying to establish the amount of methane that’s released from these lakes,” she said.
To do that, the scientists are combining old aerial photos with satellite images and new surveys of lakes across Alaska. They’re looking at how the shapes and sizes of lakes are changing over time, which is an indication of where permafrost thaw is altering the landscape. Then, they examine how changing landscapes are associated with the methane seeps. In the fall, as soon as the lakes freeze over, the bubble-measuring fieldwork begins.
“If there’s no snow on the lake and its just black ice, when you walk out you see distinct bubbles in the lake ice,” Lindgren said. The methane bubbles get trapped in the ice, fusing together in pancake shapes, that the researchers can plot and measure.
“We see a lot of these seeps clustered where the lakes are changing,” she said. The next steps will be to estimate methane release based on the extent of lake changes. And for lakes beyond the researchers’ reach, such as those in remote areas of Alaska and northwestern Canada, the goal is to estimate methane release based on how the lakes are changing, as seen in satellite images.
A new study, funded in part by ABoVE, compared old aerial photos from the 1950s with recent satellite images to measure changes in lake outlines, for example. Using this information, methane measurements, radiocarbon dating and other techniques, the scientists calculated how much old carbon, stored for thousands of years in the permafrost, has been released over the past 60 years.
“What we’re going to do is walk back in time,” said Matthew Sturm, standing in front of a doorway that led into a hillside north of Fairbanks, Alaska.
Through the doors was a tunnel that provides access to the Alaska of 40,000 years ago, when bison and mammoths foraged in grassy valleys. Now, however, the grasses and the animal bones are frozen in the ground in the Permafrost Tunnel.
The tunnel, run by the U.S. Army’s Cold Regions Research and Engineering Laboratory, was dug in the 1960s and is the site of much research into permafrost—ground that stays frozen throughout the year, for multiple years. Sturm, a professor and snow researcher at the University of Alaska, recently led a group with NASA’s Arctic Boreal Vulnerability Experiment (ABoVE) to the site. The walls of the tunnel expose the silt, ice, and carbon-rich plant and animal matter that has been frozen for tens of thousands of years.
“It’s a legacy of the Ice Age,” Sturm said. Roots of long-buried grasses hang from the ceiling, in a few places bones of Pleistocene mammals are embedded in the wall.
What will happen to the carbon contained in permafrost in the Alaska interior and elsewhere in the northern latitudes is a major question for NASA’s ABoVE campaign, which is studying the impacts of climate change on Alaska and northwestern Canada. Temperatures are rising in the Arctic region, which means permafrost is thawing at faster rates—and when it thaws, it releases carbon dioxide or methane into the atmosphere.
One ABoVE project is taking steps to monitor the temperatures of the permafrost across Alaska to see how far below the surface it is frozen and whether the temperatures of the soil layers are changing.
“We’ll get temperature data across large territories to supplement the existing data,” said Dmitry Nicolsky, with the University of Alaska, Fairbanks. Most of the existing data is along easy-to-access roads—but there aren’t many roads in Alaska. Nicolsky and his colleagues are working with researchers at USArray, which is establishing earthquake-monitoring stations across the state. Those crews are also drilling about 20 boreholes for thermometers this year, with more planned.
Nicolsky has been getting the instruments ready for deployment. Crews will install lines that have six temperature sensors at six different depths, from just below the top mossy layer to more than 6.5 feet below the surface. They’ll take readings several times a day for three to five years to help the scientists get a more complete picture of how temperatures in Arctic soil are changing.
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.”
It’s the morning meeting before the day’s flight on Thursday, Aug. 4. Fingers are clacking away at laptop keyboards. Starburst and Jolly Ranchers are scattered across a long table.
Almost as colorful as the candy are the weather maps projected onto the wall. They show a weather front slicing clean through Nebraska. Storms are likely later in the day. We’ll soon be chasing carbon dioxide and methane around both sides of the front in NASA’s C-130 Hercules research aircraft.
The flight is part of the Atmospheric Carbon and Transport–America, or ACT-America, campaign, which is investigating how weather systems and other atmospheric phenomena affect the movement of the two greenhouse gases in the atmosphere.
Our flight path will take us into the northwest corner of Missouri then back north through Nebraska and into South Dakota.
“We’re going after something that should be dominated by transport,” says Ken Davis, principal investigator for ACT-America from Penn State.
Looking at flight scenarios for upcoming days, ACT-America instrument scientist Josh DiGangi of NASA’s Langley Research Center in Hampton, Virginia, suggests an ambitious path that involves a spiral pattern.
“Oh, that just makes my head hurt,” Davis says.
In the minutes before everyone heads out to the aircraft, a reporter from the Lincoln Journal Star calls. He’s hoping to find out what NASA is doing in Lincoln.
It’s a fair question. Amid the hubbub of people prepping for the flight, Davis explains to the reporter that the Midwest is a region ripe with greenhouse gas fluxes, or areas where lots of greenhouse gases are exchanged between the biosphere on land and the atmosphere.
Agriculture is a huge factor. The vast, seemingly endless fields of corn and soybean in the area gobble up a lot of carbon dioxide. Cows and other livestock produce copious amounts of methane. Coal operations in Wyoming, and oil and gas production in the Dakotas contribute to the complex atmospheric chemistry as well.
“It’s the kind of ecosystem we want to understand,” Davis tells the reporter.
Weather plays a factor, too. Big storms churn up the gases and move them around.
“This is where the storms form,” Davis says. “Many mid-latitude cyclones are born on the eastern slope of the Rockies.”
On the C-130, not long after takeoff, Davis climbs the stairs into the cockpit.
“After we get to the end of this,” he says, gesturing out at the clouds, “we’re going to spiral down, turn around and fly at about 1,000 feet.” He moves his hands up and down to simulate turbulence. “That’s usually pretty fun.”
And it is. The first time. Another bouncy low-altitude run later in the flight puts my inner ear to the test.
Other than that, though, it’s a relatively smooth, comfortable ride — even with a fair number of altitude changes. Those changes are important. They allow the science instruments to gather data in different layers of the atmosphere.
Also, as Josh DiGangi puts it: “Remote sensing instruments like to be up high; in situ instruments like to be down low.”
In fact, the remote sensing lidar instruments can be dangerous at lower altitudes. A zap from one of the lasers could do real damage to the eyes of someone looking up through a pair of binoculars. That’s why lidar instruments have to be turned off at altitudes below 6,000 feet.
As he watches real-time data from his in situ instruments scroll across a computer monitor, DiGangi occasionally reaches into a nearby storage bin and pulls out handfuls of pretzels or cheddar popcorn. He offers to share.
“But don’t eat my banana,” he says. “That’s my banana.”
He’s joking. Sort of. But snacks and drinks are relatively easy to come by on the aircraft, anyway. There’s a microwave, a little refrigerator and even a coffee maker.
After five mostly nausea-free hours in the air, the C-130 lands back in Lincoln.
“[Lincoln’s] not as exciting as traveling to some exotic part of the world,” Davis joked to the newspaper reporter that morning.
He’s right. It’s not exotic. But following a vicious thunderstorm that rips through Lincoln a couple of hours after the flight touches down, a vivid double rainbow arcs over the airport. It’s visible from end to end. Yeah, it’s not tropical beaches and palm trees, but it’s a beautiful sight nonetheless.
Flying airborne science missions requires skill, patience and adaptability.
The C-130H pilots flying now over the eastern United States measuring carbon dioxide and methane for NASA’s ACT-America field campaign are asked to fly precise routes, giving scientists an opportunity to gather very specific sets of data on sources, absorption and movement of these gases.
Readings taken by instruments aboard the aircraft will be compared to those collected on the ground, aboard a second ACT-America aircraft, and from a satellite on orbit. Making apples-to-apples comparisons means following exact flight profiles while shepherding the airplane through weather that’s not always sunny and mild.
Pilot Jim Lawson draws on 28 years of flying as a Navy pilot and a civilian flight instructor, putting in more than 10,000 hours at the controls of 11 different types of aircraft. Last year, he flew more than 30 times for NASA’s Operation IceBridge.
Jeff Callaghan has made the C-130 his specialty. He’s been piloting that type of aircraft since getting his wings as a Marine in 1995. He has accumulated more than 3,000 hours in the C-130. In May, Callaghan flew as part of NASA’s North Atlantic Aerosols and Marine Ecosystems Study.
We asked Lawson and Callaghan questions about what it’s like to fly American skies in the name of science and in support of ACT-America.
What do you find the most difficult or rewarding about flying for ACT-America?
Jim Lawson: Flying for science is very challenging and interesting. We are challenged as pilots when flying NASA mission profiles and get to use the full extent of our pilot skills. The reward is knowing that the work I do benefits the advancement of science and humanity.
Flying weather-dependent missions requires flexibility. When you find you can’t fly because of adverse conditions, how do you spend your time?
JL: While on the ground, the pilots are assisting the science team in the planning of the next missions. If one flight mission cancels for any reason, we look for ways to incorporate that mission into future mission profiles. Adaptability and flexibility are key!
You previously flew for the Navy and are currently in the Naval reserves. Was it hard to make the transition to NASA missions?
JL: All of the aircrew have prior military service. We have Navy, Marines and Air Force represented on the crew. The culture and work ethic are the same and we all work well together to get the mission done. The only difference is the mission and the customer. Unlike the military, where our mission would be to support combat operations and where the customer is the Department of Defense, the mission for us now is the NASA science objectives and our customer is our NASA science team.
Communication is key to achieve the NASA mission objectives, and this can be a challenge sometimes, but since we are all professionals, we learn to speak each other’s language. The aircrew become wise in the ways of science and the scientists learn the ways of aviation.
What do you like most about being a pilot?
JL: My office always has the best view.
Does flying along weather fronts present any unusual challenges?
Jeff Callaghan: Having flown the C-130 for so many years in all kinds of weather conditions, I would say that the only unusual thing would be trying to figure out where the front is, but that is why the science team comes up with our flight paths.
Do you feel like, as a pilot on this mission, you are playing a part in helping mankind better understand the planet?
JC: In some small way, yes. A lot of people can do what I do, but there are not nearly as many people who can do what the science team does.
What do you enjoy most about being a pilot?
JC: It is hard to describe. I just love flying. I especially love flying the C-130 and working closely with my crew.
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.”
Gathering data on atmospheric carbon dioxide and methane in the skies over the U.S. East Coast can be intense.
ACT-America researchers running instruments such as the Multi-functional Fiber Laser Lidar (MFLL) and ASCENDS CarbonHawk Experiment Simulator (ACES) are generally all business as they monitor their expensive technologies built to measure greenhouse gases.
They stare intently at computer readouts telling them how instruments are functioning. They note subtle changes as their machines gather readings that will help show where carbon dioxide and methane come from and how those gases move through the air.
It’s serious work, but that doesn’t mean researchers can’t take a moment to savor the day’s accomplishments.
As soon as pilot Jim Lawson turned the C-130H homeward on July 22 after some four hours of methodical zigzagging above Maryland, Virginia, West Virginia and Pennsylvania, Yonghoon Choi decided it was time for a break.
Choi, who was in charge of the flight’s in situ (meaning “in place”) measurements, reached into a bin beside a tall rack of readouts and electronics and pulled out something tasty.
He produced a plastic bag laden with chocolate morsels, fruit chews and hard candy. Then, he hopped up from his seat and walked through the hold of the C-130H, offering his teammates something sweet.
“It’s our tradition,” Choi said, based at NASA’s Langley Research Center in Virginia. “When we’re going home, we eat candy.”
Choi is a veteran of more than a dozen airborne science campaigns like ACT-America. He’s been taking in situ measurements for some 15 years and has flown on aircraft including the DC-8, DC-12, the P-3, the Falcon and the P-20.
He explained that it’s not unusual for science flights to stretch to 8-10 hours. “After that long, everybody’s tired and ready for a treat,” Choi said, smiling.
On this flight, the ACT-America team encountered mostly clear summertime weather as they flew alternating legs at 1,000 and 10,000 feet. But there were moments of bumping and bouncing. Choi and ACT-America Principal Investigator Ken Davis stayed in close contact as the C-130H crossed in and out of what atmospheric scientists call the boundary layer.
“That was complicated today,” Davis said to Choi as the aircraft flew back toward its home base at NASA’s Wallops Flight Facility in Maryland. There was convection in the lower atmosphere and fluctuations in the boundary layer, the region of the lower troposphere where proximity to Earth’s surface creates turbulent air.
An irregular boundary layer can make measurements more difficult to parse.
“The data collection was fine, everything was working,” said Davis, a professor at Penn State University. “What we collected represents a relatively complicated state of the atmosphere.” Sources and sinks of greenhouse gasses are in action along with forces that transport them through the air.
“It’s challenging to interpret, but it doesn’t mean it can’t be interpreted,” Davis said. “The world is complicated some days.”