“We’re trying to get down into the boundary layer,” the lowest part of the atmosphere, Obland said after the biggest bump yet shook everybody aboard. “That’s where most of the action is happening, the gases we measure.”
In this phase of his work, atmospheric research, turbulence goes with the territory. You count on it, if not hope for it.
It means there’s a good chance you’re where you need to be.
Obland, who works out of NASA’s Langley Research Center in Hampton, is the project manager for an airborne experiment called Atmospheric Carbon and Transport-America – ACT-America, for short.
Begun last year, it’s a five-year, $30 million study of two key greenhouse gases – carbon dioxide and methane – and the brainchild of Ed Browell, a longtime Langley pioneer in using lasers for atmospheric research.
Thirty years ago this summer, Browell led a laser-equipped team out of Langley that flew from Chile on more than a dozen 11½-hour flights over Antarctica. Their mission: to help track a worrisome and growing hole in the ozone layer. It was part of an international scientific response to an emergency in that section of the stratosphere, more than seven miles up, that shields Earth from most of the sun’s ultraviolet radiation.
Before 1987 was over, a global treaty had established a protocol for phasing out a class of manmade chemicals called chlorofluorocarbons. Three decades later, the ozone layer is still growing healthier as a result.
The steady buildup of gases, like CO2, that are throwing a heat-trapping blanket around the globe, has proven harder to explain – and address. Though the vast majority of climate researchers believe the burning of fossil fuels and other human activities are major factors in global warming, they say not nearly enough is known about various sources of greenhouse gases. The same goes for what are known as sinks – the forests and other environments where more carbons are absorbed than generated.
Meanwhile, President Donald Trump has threatened to yank the United States from the 2015 Paris climate agreement, a United Nations accord for cutting carbon emissions that has been signed by nearly 200 countries. Trump has called global warming a hoax perpetrated by China.
Browell, who retired from NASA in 2007 and now works as a consultant to the agency, declined to wade into climate politics. But he said programs like ACT-America are vital because they collect the data necessary for sound decisions.
“We need to be continuing to investigate and refine and better understand what’s happening in the atmosphere,” he said, “because if we don’t, we’re just rolling the dice.”
Obland said the ACT-America researchers' goal can be summed up in two words: "air truth."
The experiment focuses largely on the eastern half of the United States, and takes in some parts of Texas and the Midwest as well. Before it’s over, researchers from NASA-Langley and partners including Penn State and Colorado State universities will have flown in all seasons and through a wide range of weather conditions.
Oftentimes they’re aboard two planes traveling at different altitudes simultaneously. One of them typically barrels through the boundary layer, as close as 1,000 feet above ground, where variations in carbon concentrations are the most pronounced.
The program is believed to be the most comprehensive regional study of greenhouse gases ever.
One of the main focuses is monitoring how weather systems affect the movement of CO2 and methane. Continuously measuring as they fly lines that sometimes stretches hundreds of miles, the scientists are assembling a huge geographic database of the gases’ concentrations. All of this should help climate scientists refine their estimates for how much of the gases are absorbed or generated, everywhere from cornfields to abandoned coal mines. And over time, Browell said, it should also improve the accuracy of large-scale climate change models, including those that look well into the future.
Sometimes, the researchers fly under a satellite that tracks CO2 with instruments that use sunlight reflected from Earth. They're hoping to better calibrate the orbiting lab's measuring equipment.
Browell envisions ACT-America as a bridge toward a time in which greenhouse gas-tracking lasers pointing down from space are routine. They'll be key to a continuous, detailed, comprehensive picture of the gases, he said.
Aboard the C-130 and its companion plane, a B-200, the researchers use a variety of measuring tools, but lasers are the prime focus.
Several of them were put to use on this flight on a March morning out of NASA’s Wallops Flight Facility on the Eastern Shore.
Obland was in charge of monitoring a system, crafted for potential space use, that employs technology known as differential absorption lidar. On the C-130, it involves shooting two continuous laser beams toward the ground. One is tuned to an “on” wavelength that allows it to be absorbed by a target, like CO2. The other is tuned “off” from the gas. The difference in the signals that bounce back is run through a computer, and out comes a continuously updating calculation of how many parts per million of the gas, on average, are in the column of traveling laser light.
On this day, CO2 was measuring between 406 and 412 parts per million, methane between 1.85 and 1.9 parts per million.
Up in the C-130’s cockpit, Ken Davis kept an eagle eye out for any differences. The Penn State atmospheric and climate science professor is the principal investigator for ACT-America. Davis said he and Browell first talked around 2010 about the possibility of such a program. They’re hoping that it will be followed by a similar experiment in the tropics overseas, perhaps in South America.
Davis said every ACT-America flight adds to a more complete picture of carbon fluxes – the exchange of greenhouse gases between Earth’s surface and the atmosphere.
Roughly a quarter of fossil fuel emissions are removed from the atmosphere, he said, by natural processes like plants' photosynthesis. But will shifts in weather patterns due to climate change alter that trend? The researchers' flights through different kinds of weather could help answer that question.
Davis said one of the biggest benefits of the program will be the detailed information collected on methane, considered 25 times more potent a warming gas than CO2. The researchers are trying to learn more about its sources, from old coal mines to brand-new gas-fracking operations.
But this day’s flight out of Wallops wasn’t going nearly as first planned.
A cold front was coming out of the northwest, and some warmer air from the southwest was ahead of it. Ideally, Davis said, the plane would pick its way through and “measure the change in transport in greenhouse gases on both sides” of the systems. All the way to Michigan.
Unfortunately, there was that squall line at the forward edge of the warmer air. It ran for hundreds of miles north to south, with no calm lanes to slip through. The normally turbulence-tolerant crew agreed all around that crossing this one wasn’t worth the risk.
So they’d fly west until they ran up against it, then head back east and out over the Atlantic before turning back to Wallops.
The B-200, after taking off from Langley Air Force Base, would do pretty much the same – but lower, where the going would be really rough, down around 1,000 feet much of the way.
For Davis and his team, what had started out as a planned five-hour flight ended after three hours and six minutes.
The most interesting part of the C-130’s trip was around the squall line, Davis said, as CO2 was measured at concentrations at 19,000 feet that were at roughly the same levels as in the boundary layer. Normally, concentrations are lower up there.
“Which could mean that thunderstorm line was sucking the air up and dumping it out in the upper atmosphere,” he said.
Afterward, the scientists and flight crew gathered in a conference room adjacent to the Wallops hangar bay. It was worth the short time in the air, Davis said.
But “a bummer we couldn’t get across that sucker,” he said. “It would have been fun: the data. Not the flying. The data.”
©2017 The Virginian-Pilot (Norfolk, Va.) Distributed by Tribune Content Agency, LLC.
