17 October 2017
adapted from the story by NOAA Communications
Thirty years after NASA and NOAA launched a groundbreaking airborne campaign to study the Antarctic ozone hole, the two federal science agencies have once again joined forces over the world's highest, driest and coldest continent to sniff out the secrets of the atmosphere.
On 14 October, NASA's heavily instrumented DC-8 flew over Antarctica as part of the Atmospheric Tomography Mission (ATom), an unprecedented effort to sample the remote atmosphere to understand the distribution of man-made pollutants and short-lived greenhouse gases.
"The atmospheric measurements that ATom takes are unavailable by any other means," said NOAA scientist Tom Ryerson. "ATom is designed to tell us the current state of 80 percent of Earth's atmosphere. It will give us an important and unique reality check on the computer models we use to predict the future."
The science of 'then' informs the science of 'now'
In 1987, it was another planetary puzzle that brought NASA and NOAA together. The ozone hole had just been discovered and the joint mission to Antarctica was designed to help resolve questions about which of several competing theories were responsible for the seasonal depletion of stratospheric ozone.
Results from the mission helped galvanize international efforts to control the ozone-depleting chlorine- and bromine-containing chemicals that scientists determined were the primary cause of the problem. Since its adoption in September 1987, the Montreal Protocol has significantly reduced emissions of ozone-depleting chemicals from the United States.
ATom is a five-year, NASA-funded program to gather airborne data in the remote atmosphere to identify the sources, global distribution, and effects of the three most important short-lived climate-forcing agents: methane, tropospheric (low-altitude) ozone, and black carbon soot particles.
Ryerson said that understanding these short-lived climate forcing agents would help policymakers develop strategies to control emissions and thereby buy time to address the long-lived emissions of carbon dioxide. Harvard scientist Steven Wofsy leads the project. Ryerson, who leads the tropospheric chemistry program for NOAA ESRL's Chemical Science Division, is the mission's science team lead.
A high-flying laboratory that collects a world of data
To gather data for ATom, the world's largest chemically instrumented research aircraft – the NASA DC-8 – flies a continuous up-and-down pattern from 500 feet above the wave tops to over 40,000 feet in altitude, in a dozen 10-hour flights over the course of six weeks. From its home base in Palmdale, California, the plane, with its complement of flight crew, maintenance crew and scientists, heads towards the North Pole, then hops, skips and jumps back down the Pacific towards the South Pole. Once it passes over Antarctica, the plane heads over the Atlantic Ocean towards the North Pole and then home again to California.
Ozone is one of over 200 gases and atmospheric particles being measured by the science team aboard the NASA DC-8. These include the primary greenhouse gases (like carbon dioxide and methane) and nitrogen oxides, ozone-depleting man-made pollutants and other trace gases and particles.
In 1987, NOAA scientist David Fahey was one of the principal investigators on the Airborne Antarctic Ozone Experiment (AAOE) mission. "These were challenging conditions," said Fahey, currently director of the Chemical Sciences Division. "This was before internet communications or cell phones. Now we're working with much better instruments and modeling tools, but the goal is the same: discovering the essential details about how the atmosphere works in the vast remote regions of the planet."