Air Quality & Pollution

U.S. gains in air quality are slowing down

BOULDER, Colo. — After decades of progress in cleaning up air quality, U.S. improvements for two key air pollutants have slowed significantly in recent years, new research concludes. The unexpected finding indicates that it may be more difficult than previously realized for the nation to achieve its goal of decreased ozone pollution, scientists said."Although our air is healthier than it used to be in the 80s and 90s, air quality in the U.S. is not progressing as quickly as we thought," said National Center for Atmospheric Research (NCAR) scientist Helen Worden, a co-author. "The gains are starting to slow down."The study, by an international team of researchers, analyzed extensive satellite and ground-based measurements of nitrogen oxides and carbon monoxide. They found that levels of pollutants that can contribute to the formation of ground-level ozone, or smog, have failed to continue a fairly steady decline as estimated by the U.S. Environmental Protection Agency."We were surprised by the discrepancy between the estimates of emissions and the actual measurements of pollutants in the atmosphere," added Zhe Jiang, the lead author of the study. "These results show that meeting future air quality standards for ozone pollution will be more challenging than previously thought."Jiang, who conducted much of the research during a postdoctoral fellowship at NCAR, is now with the University of Science and Technology of China.The study will be published next week in the Proceedings of the National Academy of Sciences. The research was funded primarily by NASA, the National Oceanic and Atmospheric Administration, the University of Colorado Boulder, and the National Science Foundation, which sponsors NCAR.Slowdown in air quality improvement. Estimates by the Environmental Protection Agency indicate that levels of nitrogen oxides have continued their decline over the past decade. But top-down emission estimates using satellite measurements show that the decline has slowed dramatically in recent years. (Figure by Zhe Jiang, redrawn by Simmi Sinha, UCAR.)Revealing the slowdownNitrogen oxides and carbon monoxide contribute to the formation of ground-level ozone, a pollutant that is harmful to human health and the environment. Levels of the pollutants have declined significantly since passage of the 1970 Clean Air Act, which spurred development of emission-reducing technologies, such as catalytic converters on automobiles and low nitrogen oxide burners at power plants.A number of cities and outlying areas in the United States, however, remain out of compliance with EPA standards for ozone, which the agency made more stringent in 2015.EPA emission estimates are based on monitored readings or engineering calculations of pollutants emitted by vehicles, factories, or other sources.To obtain a fuller picture of national pollution levels, Jiang and his co-authors turned to satellite instruments that measure levels of nitrogen oxides and carbon monoxide. They analyzed these atmospheric observations with advanced computer simulations and statistical analyses, both to quantify pollutant concentrations and to map their concentrations across the contiguous United States. They then corroborated their findings with observations from air quality monitoring stations that measure local pollution levels.The results showed that emission reductions slowed down dramatically in the five-year period from 2011 to 2015 compared to 2005 to 2009. Whereas nitrogen oxide concentrations dropped by 7 percent yearly from 2005 to 2009, they declined by just 1.7 percent yearly from 2011 to 2015—a 76 percent slowdown. Those findings contrast with EPA emission inventories, which put the slowdown at only 16 percent during the same time period.Similarly, the study showed that carbon monoxide levels have declined much more slowly in recent years.The research team originally thought that emissions from Asia could be playing a role, but this was not supported by the data. The measurements showed that the slowdown in improved air pollution levels was particularly pronounced in the eastern United States, one of several signs that the pollutants were not coming in from overseas.The authors concluded that some of the reasons for the discrepancy for nitrogen oxides may be:the decreasing relative contributions of gasoline cars to the pollutant, due to the ongoing effectiveness of three-way catalytic converters;the increasing relative emissions of nitrogen oxides from such sources as industrial, residential, and commercial boilers and off-road vehicles; andslower-than-expected reductions in emissions by heavy-duty diesel trucks that have newer (and still maturing) catalytic converter technologies.The study concluded that the slowdown in carbon monoxide, which is largely emitted by cars, is likely due to the large gains that have already been achieved by equipping cars with three-way catalytic converters."As you become effective at controlling emissions from cars and power plants, the other sources become more important and there's less information about them," said co-author Brian McDonald, a scientist with the National Oceanic and Atmospheric Administration and the Cooperative Institute for Research in Environmental Sciences.The authors said that follow-up research, combining EPA inventories with a new generation of increasingly sophisticated satellite instruments, would lead to a more detailed understanding about how pollution is changing in response to emission controls."The top-down satellite measurements and the inventories provide complementary data that will enable us to get better estimates of the emission sources," McDonald said. "It will be useful to learn more about why the discrepancies exist and why the trend toward better air quality is slowing down."About the studyTitle: Unexpected slowdown of US pollutant emission reduction in the last decadeAuthors: Zhe Jiang, Brian C. McDonald, Helen Worden, John R. Worden, Kazuyuki Miyazaki, Zhen Qu, Daven K. Henze, Dylan B. A. Jones, Avelino F. Arellano, Emily V. Fischer, Liye Zhu, and K. Folkert BoersmaPublication: Proceedings of the National Academy of SciencesChanges in Nitrogen Dioxide (NO2) levels. These satellite observations show the changes in NO2 during two recent periods. From 2005 to 2009, NO2 levels declined sharply across much of the United States, as shown in the areas of darkest blue. But in more recent years, NO2 has declined more slowly and even increased slightly in some areas (light red).  The total column NO2 observations (1 unit = 1000 trillion molecules per square centimeter) are from the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite. (Figure by Zhe Jiang, redrawn by Simmi Sinha, UCAR.)

Scientists pinpoint sources of Front Range ozone

BOULDER, Colo. — A comprehensive new air quality report for the state of Colorado quantifies the sources of summertime ozone in Denver and the northern Front Range, revealing the extent to which motor vehicles and oil and gas operations are the two largest local contributors to the pollutant.The new report, based on intensive measurements taken from aircraft and ground sites as well as sophisticated computer simulations, also concludes that unhealthy levels of ozone frequently waft up to remote mountain areas, including Rocky Mountain National Park.Scientists at the National Center for Atmospheric Research (NCAR) wrote the report with support from colleagues at NASA, drawing on a pair of 2014 field campaigns that tracked both local and distant contributors to pollution on the northern Front Range. The research was funded by the Colorado Department of Public Health and Environment (CDPHE), NASA, and the National Science Foundation, which is NCAR's sponsor."We found that, on high ozone days, a critical portion of the ozone pollution here on the Front Range is the result of local activities, especially traffic and oil and gas operations," said NCAR scientist Gabriele Pfister, an author of the new report. "The pollution doesn't just affect the metro area. Prevailing daytime winds often transport the ozone to the west, exposing the foothills and mountains to high ozone levels."Scientists involved in the 2014 field campaigns have published some of the findings in peer-reviewed scientific journals.The report is designed to provide information to the CDPHE, which is working to reduce unhealthy levels of ozone in the Northern Colorado Front Range Metropolitan Area that stretches from Denver's southern suburbs to Fort Collins.“The NCAR analysis provides important information that helps inform our ongoing efforts to better understand ozone formation and craft cost-effective strategies to reduce ozone levels and protect public health,” said Larry Wolk, executive director and chief medical officer at the Colorado Department of Public Health and Environment.This visulization of surface ozone across the Front Range on an August afternoon shows how ozone pollution can sometimes be more accute in the high mountains than on the populated plains, depending on local winds. (©UCAR. This image is freely available for media & nonprofit use.)Tracing an invisible gasAn invisible but harmful pollutant, ground-level ozone can lead to increased asthma attacks and other respiratory ailments, producing symptoms that include coughing, trouble breathing, and chest pain. It also can be damaging to vegetation, including crops.Ozone can be challenging to trace because it is the product of other pollutants. It forms in the atmosphere from chemical reactions of hydrocarbons and carbon monoxide in the presence of nitrogen oxides and sunlight. It peaks during the summer, when sunshine is most abundant.Denver has a background ozone level of about 40-50 parts per billion (ppb) that is generated by numerous sources outside of the region. With the additional ozone generated by local emissions, the area on summer days often exceeds the federal health standard, which is set at an average of 70 ppb over an eight-hour period.The report finds that cars, trucks, and other motor vehicles are the primary local contributors to ozone in the heavily developed urban corridor that stretches from Denver's southern suburbs to about the city of Boulder. Further north, however, emissions from oil and gas operations are the primary local contributors to ozone between Boulder and Fort Collins. Motor vehicles and oil and gas operations each contribute, on average, 30-40 percent to total local ozone production in the region on days when ozone exceeds the health standard, the report states.Depending on prevailing winds, the air masses from the southern and northern parts of the metro area sometimes mix, enabling emissions from a variety of sources to produce ozone more readily. These sources include power plants, industrial facilities, and Denver International Airport.The scientists warned of the potential for more ozone pollution to accompany expected population increases."The Denver metropolitan area will keep growing," said NCAR scientist Frank Flocke, a co-author of the report. "Total miles driven will keep increasing."However, computer simulations run by the research team indicated that lowering local emissions could result in substantial ozone reductions. In some scenarios, ozone could be reduced by 6-10 ppb, which could make the difference between meeting or exceeding the national ambient air quality standards for ozone.Leveraging two research projectsThe report was commissioned as part of a major field project in the summer of 2014 led by Pfister and Flocke. The Front Range Air Pollution and Photochemistry Experiment (FRAPPÉ) relied on specially equipped aircraft, mobile radars, balloon-mounted sensors, and advanced computer models to measure emissions from industrial facilities, power plants, motor vehicles, agricultural operations, oil and gas drilling, fires, and other human-related and natural sources.The FRAPPÉ team coordinated with a NASA-led air quality mission that took place on the Front Range at the same time: DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality).Colorado, like other states, relies on a limited number of ground-based stations to monitor air quality and help guide statewide policies and permitting. The field projects provided a much more detailed and complete, three-dimensional picture of the processes that affect air quality, including conditions far upwind and high up in the atmosphere.The new report recommends additional monitoring of pollutants that lead to ozone formation at key ground sites. It also recommends comprehensive aircraft studies in the future to monitor air quality along the Front Range as the population increases and emissions sources change.The report, "Process-Based and Regional Source Impact Analysis for FRAPPÉ and DISCOVER-AQ 2014," was submitted to the CDPHE in July and published online earlier this month.

Dino-killing asteroid could have thrust Earth into two years of darkness

BOULDER, Colo. — Tremendous amounts of soot, lofted into the air from global wildfires following a massive asteroid strike 66 million years ago, would have plunged Earth into darkness for nearly two years, new research finds. This would have shut down photosynthesis, drastically cooled the planet, and contributed to the mass extinction that marked the end of the age of dinosaurs.These new details about how the climate could have dramatically changed following the impact of a 10-kilometer-wide asteroid will be published Aug. 21 in the Proceedings of the National Academy of Sciences. The study, led by the National Center for Atmospheric Research (NCAR) with support from NASA and the University of Colorado Boulder, used a world-class computer model to paint a rich picture of how Earth’s conditions might have looked at the end of the Cretaceous Period, information that paleobiologists may be able to use to better understand why some species died, especially in the oceans, while others survived.Scientists estimate that more than three-quarters of all species on Earth, including all non-avian dinosaurs, disappeared at the boundary of the Cretaceous-Paleogene periods, an event known as the K-Pg extinction. Evidence shows that the extinction occurred at the same time that a large asteroid hit Earth in what is now the Yucatán Peninsula. The collision would have triggered earthquakes, tsunamis, and even volcanic eruptions.Scientists also calculate that the force of the impact would have launched vaporized rock high above Earth's surface, where it would have condensed into small particles known as spherules. As the spherules fell back to Earth, they would have been heated by friction to temperatures high enough to spark global fires and broil Earth's surface. A thin layer of spherules can be found worldwide in the geologic record."The extinction of many of the large animals on land could have been caused by the immediate aftermath of the impact, but animals that lived in the oceans or those that could burrow underground or slip underwater temporarily could have survived," said NCAR scientist Charles Bardeen, who led the study. "Our study picks up the story after the initial effects — after the earthquakes and the tsunamis and the broiling. We wanted to look at the long-term consequences of the amount of soot we think was created and what those consequences might have meant for the animals that were left."Other study co-authors are Rolando Garcia and Andrew Conley, both NCAR scientists, and Owen “Brian” Toon, a researcher at the University of Colorado Boulder.An illustration of an asteroid impacting Earth. (Image courtesy NASA.)A world without photosynthesisIn past studies, researchers have estimated the amount of soot that might have been produced by global wildfires by measuring soot deposits still preserved in the geologic record. For the new study, Bardeen and his colleagues used the NCAR-based Community Earth System Model (CESM) to simulate the effect of the soot on global climate going forward. They used the most recent estimates of the amount of fine soot found in the layer of rock left after the impact (15,000 million tons), as well as larger and smaller amounts, to quantify the climate's sensitivity to more or less extensive fires.In the simulations, soot heated by the Sun was lofted higher and higher into the atmosphere, eventually forming a global barrier that blocked the vast majority of sunlight from reaching Earth's surface. “At first it would have been about as dark as a moonlit night," Toon said.While the skies would have gradually brightened, photosynthesis would have been impossible for more than a year and a half, according to the simulations. Because many of the plants on land would have already been incinerated in the fires, the darkness would likely have had its greatest impact on phytoplankton, which underpin the ocean food chain. The loss of these tiny organisms would have had a ripple effect through the ocean, eventually devastating many species of marine life.The research team also found that photosynthesis would have been temporarily blocked even at much lower levels of soot. For example, in a simulation using only 5,000 million tons of soot — about a third of the best estimate from measurements — photosynthesis would still have been impossible for an entire year.In the simulations, the loss of sunlight caused a steep decline in average temperatures at Earth's surface, with a drop of 50 degrees Fahrenheit (28 degrees Celsius) over land and 20 degrees Fahrenheit (11 degrees Celsius) over the oceans.While Earth's surface cooled in the study scenarios, the atmosphere higher up in the stratosphere actually became much warmer as the soot absorbed light from the Sun. The warmer temperatures caused ozone destruction and allowed for large quantities of water vapor to be stored in the upper atmosphere. The water vapor then chemically reacted in the stratosphere to produce hydrogen compounds that led to further ozone destruction. The resulting ozone loss would have allowed damaging doses of ultraviolet light to reach Earth's surface after the soot cleared.The large reservoir of water in the upper atmosphere formed in the simulations also caused the layer of sunlight-blocking soot to be removed abruptly after lingering for years, a finding that surprised the research team. As the soot began to settle out of the stratosphere, the air began to cool. This cooling, in turn, caused water vapor to condense into ice particles, which washed even more soot out of the atmosphere. As a result of this feedback loop — cooling causing precipitation that caused more cooling — the thinning soot layer disappeared in just a few months.Challenging the modelWhile the scientists think the new study gives a robust picture of how large injections of soot into the atmosphere can affect the climate, they also caution that the study has limitations.For example, the simulations were run in a model of modern-day Earth, not a model representing what Earth looked like during the Cretaceous Period, when the continents were in slightly different locations. The atmosphere 66 million years ago also contained somewhat different concentrations of gases, including higher levels of carbon dioxide.Additionally, the simulations did not try to account for volcanic eruptions or sulfur released from the Earth's crust at the site of the asteroid impact, which would have resulted in an increase in light-reflecting sulfate aerosols in the atmosphere.The study also challenged the limits of the computer model's atmospheric component, known as the Whole Atmosphere Community Climate Model (WACCM)."An asteroid collision is a very large perturbation — not something you would normally see when modeling future climate scenarios," Bardeen said. "So the model was not designed to handle this and, as we went along, we had to adjust the model so it could handle some of the event's impacts, such as warming of the stratosphere by over 200 degrees Celsius."These improvements to WACCM could be useful for other types of studies, including modeling a "nuclear winter" scenario. Like global wildfires millions of years ago, the explosion of nuclear weapons could also inject large amounts of soot into the atmosphere, which could lead to a temporary global cooling."The amount of soot created by nuclear warfare would be much less than we saw during the K-Pg extinction," Bardeen said. "But the soot would still alter the climate in similar ways, cooling the surface and heating the upper atmosphere, with potentially devastating effects."Writer:Laura Snider, Senior Science Writer

NCAR to host Air Quality Open House on May 3 in Boulder

BOULDER, Colo. — The National Center for Atmospheric Research (NCAR) is marking Air Quality Awareness Week with a family-friendly open house at its Mesa Lab in southwest Boulder from 5-8 p.m. on Wednesday, May 3.A "brown cloud" of smog seen over Boulder, Colorado. (©UCAR. This image is freely available for media & nonprofit use.)The free hands-on event will provide opportunities for visitors to learn about air pollution: what it is, how it's measured, what its impacts are, and how it's regulated. Visitors are encouraged to come with questions, and scientists will be on hand to provide answers, about air quality in general and Colorado's Front Range in particular."This will be everything you ever wanted to know about air quality," said Eileen Carpenter, an education specialist at the University Corporation for Atmospheric Research (UCAR), which manages NCAR. "We've partnered with organizations from around the region to bring together experts on a diverse range of air quality topics, from monitoring pollution from space to monitoring methane leaks from oil and gas operations right here on the Front Range."Partner organizations include the Colorado Department of Public Health and Environment, the Regional Air Quality Council, GO3–Global Ozone Project, the University of Colorado Environmental Engineering Program, the National Park Service, Ball Aerospace, Boulder County Public Health, and NASA.Activities will include learning how plants react to smog in NCAR's "ozone garden," exploring a mobile air monitoring lab, and participating in experiments designed to help kids understand how air pollution works. Some organizations will also be displaying the instruments they use to measure air quality, and NCAR will host an ask-a-scientist table.During the event, visitors can also check out the permanent air quality exhibit that was recently installed on the first floor of the Mesa Lab. The exhibit explains the different types of pollution — including ozone and particulates — and allows the viewer to interact with a live feed of air quality measurements taken from instruments on top of the Mesa Lab.What: NCAR Air Quality Open HouseWhere: Mesa Lab, 1850 Table Mesa Dr., Boulder, CO, 80305When: 5-8 p.m., Wednesday, May 3, 2017For more information, visit the event website. Writer:Laura Snider, Senior Science Writer and Public Information Officer

UCAR staff add climate storybook to Elementary GLOBE's line-up

March 2, 2017 | In a new illustrated storybook, a group of school children travel with a scientist to Greenland and the Maldives to learn about tools used to study climate change and its impacts. After seeing the challenge of melting glaciers and rising seas, the students come back with ideas on how to reduce their own greenhouse emissions.What in the World is Happening to Our Climate? introduces new material to a series of children's adventure science books published by Elementary GLOBE (part of the Global Learning and Observations to Benefit the Environment program).The newest storybook, funded by NASA Langley Research Center, is the product of a partnership between staff in two University Corporation for Atmospheric Research programs: the GLOBE Implementation Office and the UCAR Center for Science Education, or SciEd. SciEd supports the education and outreach efforts of the National Center for Atmospheric Research (NCAR), which UCAR manages with sponsorship by the National Science Foundation.The climate book is available for download at no charge:Becca Hatheway, SciEd's manager of teaching and learning, said NASA asked UCAR a couple of years ago to create educational resources for children in advance of the installation of the Sage III instrument on the International Space Station to measure ozone and aerosols in Earth’s atmosphere. (Sage III was installed last month).The result was What's Up in the Atmosphere: Exploring Colors in the Sky, a storybook featuring children who learn about the colors of the sky and their relationship to air quality through observations and photos. Hatheway and Kerry Zarlengo, a former elementary school teacher and literacy coach, wrote the book in 2015.During discussions about the air quality project, "we pitched the idea of doing a climate change book as well, and NASA was supportive," Hatheway said. "We've always wanted to do one on this topic — it's in the NCAR wheelhouse."UCAR's Elementary GLOBE's new climate storybook is geared to children in grades K-4. (©UCAR. Illustration by Lisa Gardiner. This image is freely available for media & nonprofit use.)Hatheway co-wrote the text for the climate book with Diane Stanitski, a deputy director at the National Oceanic and Atmospheric Administration's Earth System Research Laboratory in Boulder. The Elementary GLOBE series, which now numbers seven storybooks, is aimed at introducing K-4 students to Earth system science. The first five books focus on clouds, water, phenology, soils, and the Earth system. NASA is funding an update of those books, some of which are more than a decade old.Books are field tested by teachers, and the modules come with learning activities and a teacher's guide and glossary. The idea is that younger children will be guided in the reading and activities, while older children can learn more independently.Most of the storylines focus on a group of school children who go on adventures to learn and collect data about a topic.Lisa Gardiner, whose role at UCAR includes developing educational resources, has illustrated all of the books in the series. She said the climate book holds special meaning for her."It's at the root of what we do at SciEd," Gardiner said. "A lot of young kids want to know about climate change, but there aren't that many resources for their age group."Gardiner said she tries to make her illustrations as realistic as possible. To learn more about the Maldives, Gardiner asked Alison Rockwell of NCAR's Earth Observing Laboratory for photos from a field campaign several years ago. "I wanted to know what the houses looked like, what the people were wearing."The activities are realistic, too. The climate book's activities include building a model of a coastal community, predicting which features would be at risk of flooding, and then "flooding" the model to see the results.Children learning about wind energy in the new Elementary GLOBE climate storybook. (©UCAR. Illustration by Lisa Gardiner. This image is freely available for media & nonprofit use.)Julie Malmberg, a GLOBE project manager, said the storybooks and learning activities can be downloaded for free, or educators can purchase a hard copy of the entire module for the cost of the printing and binding. She has heard from school officials, such as one in a West Virginia district, using the resources for grade-school teacher training.Most educators, Malmberg said, download the materials. Between 2012-2016, GLOBE recorded 42,533 storybook downloads and 54,197 downloads of learning activities. Do You Know Clouds Have Names, co-authored with NCAR Senior Scientist Emerita Peggy LeMone, is the most popular storybook, while the most popular learning activities are connected to a book called The Scoop on Soils.Hatheway said SciEd plans to provide copies of the climate change and sky color books to teachers who attend its professional development workshops or programs at the Mesa Lab, as well as at conferences SciEd staffers attend. NOAA plans to distribute the climate book at the National Science Teachers Association conference this spring.While the storybooks were developed for the educational community in the U.S., some have been translated into other languages and distributed by GLOBE partners in other countries.The GLOBE Program is an international science and education program that provides students and the public worldwide with the opportunity to participate in the scientific process and contribute to understanding of the Earth system and global environment.Writer/contactJeff Smith, Science Writer and Public Information Officer   

Indonesian fires exposed 69 million to 'killer haze'

November 16, 2016 | NCAR scientist Christine Wiedinmyer is a co-author of a new study into the health effects of the 2015 Indonesian wildfires. This is an excerpt from a news release issued by Newcastle University.  Wildfires in Indonesia and Borneo exposed 69 million people to unhealthy air pollution, new research has shown.An image taken from space of smoke billowing from fires in Jambi Province on the Indonesian island of Sumatra. The false-color image was made with a combination of visible (green) and infrared light so that fires and freshly burned land stand out. (Image courtesy NASA.)The study, published today in Scientific Reports, gives the most accurate picture yet of the impact on human health of the wildfires which ripped through forest and peatland in Equatorial Asia during the autumn of 2015.The study used detailed observations of the haze from Singapore and Indonesia. Analysing hourly air quality data from a model at a resolution of 10km – where all previous studies have looked at daily levels at a much lower resolution - the team was able to show that a quarter of the population of Malaysia, Singapore and Indonesia was exposed to unhealthy air quality conditions between September and October 2015.Estimating between 6,150 and 17,270 premature deaths occurred as a direct result of the polluted haze, the research team – involving academics from the UK, US, Singapore and Malaysia – said the study confirmed the extent of this public health crisis.Read the full news release by Newcastle University.About the articleTitle: Population exposure to hazardous air quality due to the 2015 fires in Equatorial AsiaAuthors: P. Crippa, S. Castruccio, S. Archer-Nicholls, G. B. Lebron, M. Kuwata, A. Thota, S. Sumin, E. Butt, C. Wiedinmyer, and D. V. SpracklenJournal: Scientific Reports, DOI: 10.1038/srep37074

Scientists observe first signs of healing in the Antarctic ozone layer

NCAR scientists Doug Kinnison and Michael Mills are co-authors on a new study published today in the journal Science. This is an excerpt from a news release by the Massachusetts Institute of Technology, a UCAR member institution, about the study.This animation shows the opening and closing of the Antarctic ozone hole (dark blue) in 2015. (Animation courtesy of NASA.)June 30, 2016 | Scientists at MIT and elsewhere have identified the “first fingerprints of healing” of the Antarctic ozone layer, published today in the journal Science.The team found that the September ozone hole has shrunk by more than 4 million square kilometers — about half the area of the contiguous United States — since 2000, when ozone depletion was at its peak. The team also showed for the first time that this recovery has slowed somewhat at times, due to the effects of volcanic eruptions from year to year. Overall, however, the ozone hole appears to be on a healing path.The authors used “fingerprints” of the ozone changes with season and altitude to attribute the ozone’s recovery to the continuing decline of atmospheric chlorine originating from chlorofluorocarbons (CFCs). These chemical compounds were once emitted by dry cleaning processes, old refrigerators, and aerosols such as hairspray. In 1987, virtually every country in the world signed on to the Montreal Protocol in a concerted effort to ban the use of CFCs and repair the ozone hole.“We can now be confident that the things we’ve done have put the planet on a path to heal,” says lead author Susan Solomon, the Ellen Swallow Richards Professor of Atmospheric Chemistry and Climate Science at MIT. “Which is pretty good for us, isn’t it? Aren’t we amazing humans, that we did something that created a situation that we decided collectively, as a world, ‘Let’s get rid of these molecules’? We got rid of them, and now we’re seeing the planet respond.”Solomon’s co-authors include Diane Ivy, research scientist in the Department of Earth, Atmospheric and Planetary Sciences, along with researchers at the National Center for Atmospheric Research in Boulder, Colorado, and the University of Leeds in the U.K.Read the full release at MIT News.About the articleTitle: Emergence of Healing in the Antarctic Ozone Layer Authors: Susan Solomon, Diane J. Ivy, Doug Kinnison, Michael J. Mills, Ryan R. Neely, and Anja SchmidtJournal: Science, DOI: 10.1126/science.aae0061

Planes, ships and satellites: Investigating air quality in Korea

May 12, 2016 | Scientists from the National Center for Atmospheric Research are on the ground in South Korea as part of a field campaign to investigate the region's air quality. Between May 1 and June 12, NCAR scientists and their colleagues from NASA, U.S. and South Korean universities, and South Korea’s National Institute of Environmental Research (NIER) will collect observations from airborne labs, ships, satellites, and ground-based instruments. The campaign, which involves more than 580 researchers from 72 institutions, is called KORUS-AQ (Korea U.S.-Air Quality study). "These observations will help us develop a much better understanding of the various complex factors controlling air quality over the Korean Peninsula," said NCAR scientist Louisa Emmons, who is on site with KORUS-AQ. "The observations will help improve air quality models, and in turn, those models will help us interpret the current, as well as future, observations." This 2007 NASA satellite image shows a swath of air pollution sweeping east across the Korean peninsula to Japan. (Image courtesy NASA.) South Korea offers a rare opportunity to separate the diverse factors that contribute to air quality. For example, Seoul, the capital of South Korea, is one of the world's five most-populated metropolitan areas, but it is surrounded by rural, forested land. This stark separation gives scientists the ability to differentiate the components of pollution that originate from factories, tailpipes, and other human-related sources of pollution from those that originate from natural areas, including volatile organic compounds emitted by vegetation. Because the Korean Peninsula is largely isolated by bodies of water, scientists can also more easily determine what kinds of pollution blow into the region—dust and industrial pollution from China, for example—as well as what kinds of pollution blow out of the region toward Japan. From left: NCAR scientists Sam Hall, Benjamin Gaubert, Pablo Saide, Deedee Montzka, Louisa Emmons, and Andy Weinheimer. (Photo courtesy Sam Hall.) NCAR scientists are contributing to the effort in several ways. A team led by Emmons is issuing chemical forecasts of pollution transport and formation so that the scientists taking airborne measurements can decide where, or whether, to fly. The planes being used during KORUS-AQ include a NASA DC-8, a NASA King Air, and a Korean King Air operated by Hanseo University and NIER.  Two NCAR research groups from the Atmospheric Chemistry Observations  and Modeling lab are also flying instruments onboard the DC-8. One team, led by NCAR scientist Sam Hall, is measuring the amount of light available to break down compounds in the atmosphere. The second, led by NCAR scientist Andy Weinheimer, is measuring ozone and nitrogen oxides in the atmosphere. In combination with other instruments on the aircraft, these help to characterize the photochemical history, processes, and evolution of air pollution along the flight path. Follow what's happening with KORUS-AQ at the NASA Earth Expeditions blog, or watch a video about the campaign here. Writer/contactLaura Snider, Senior Science Writer and Public Information Officer

Tracking air quality from high in the sky

October 21, 2015 | NCAR scientists have demonstrated how new types of satellite data could improve how agencies monitor and forecast air quality, both globally and by region. The scientists used computer simulations to test a method that combines analysis of chemistry-climate model output with the kind of data that could be obtained from a planned fleet of geostationary satellites, each of which would view a large area of Earth on a continuous basis from high orbit. For example, with a constellation of satellites, the system could be used to measure, track, and predict the effects of pollution emitted in Asia and transported to the western U.S., or the impacts of wildfires in the Pacific Northwest on air quality in the Midwest. A high-orbit geostationary satellite could view a large area of the Earth, such as North America in this illustration, on a continuous basis. (Image courtesy NASA/Langley Research Center). "We think the new perspective made possible by geostationary sensors would provide data that is useful for everyday air quality forecasting, as well as for early warnings about extreme events, like the effects of wildfires," said NCAR scientist Helen Worden, one of the members of the research team. The NCAR team reported their test of the system's potential in a paper co-authored with a NASA scientist that appears in the journal Atmospheric Environment. Current observations are mostly taken from low-elevation, globally orbiting satellites that provide only one or two measurements over a given location per day, thus limiting critical air quality observations, such as vehicle emissions during rush hour. ­One exception is an air quality forecasting system at the National Oceanic and Atmospheric Administration that uses geostationary sensors to provide information about tiny polluting particles known as aerosols. But that system doesn't track carbon monoxide, a primary indicator of air pollution that serves as a good chemical tracer for observing how pollutants are emitted and dispersed in the atmosphere. "Carbon monoxide lives long enough—a month or two—that you can track it around the Earth," Worden said. To fill in the data gap, several countries and space agencies plan to deploy geostationary satellites by the end of the decade to observe and monitor air pollutants over North America, Europe, and East Asia. Proof of concept The team members applied a statistical technique that they and colleagues have developed over the years to analyze data obtained by an instrument aboard NASA's globally orbiting Terra spacecraft called MOPITT (Measurement of Pollution in the Troposphere). A collaboration between the University of Toronto and NCAR, MOPITT pioneered the measurement of carbon monoxide from space. Starting with MOPITT's real-world observations, the scientists then produced a data set of hypothetical observations representative of those potentially obtainable from a constellation of geostationary satellites. They visualized their results on high-resolution maps, producing results for areas as small as 2.7 miles (7 kilometers) wide that extend as high as 7.5 miles (12 kilometers) into the atmosphere. Measurements of carbon monoxide in April 2014 from the MOPITT instrument  (Measurement of Pollution in the Troposphere) aboard NASA's globally orbiting Terra spacecraft. The boxes show the observing domains for geostationary satellites and red colors indicate high levels of carbon monoxide. (©UCAR. Image courtesy Helen Worden, NCAR. This image is freely available for media & nonprofit use.) When it comes to speed and cost, the NCAR method has several advantages. A month's worth of data, about 200 million data points, can be produced in less than 12 hours using a standard desktop computer. "The model produced very realistic results on high-resolution maps at a low computational cost," said NCAR scientist Jerome Barre, who led the study. The scientists caution that there are limitations to the new system when viewing extremely polluted areas. The team accounted for the impact of clouds in their model to simulate the most realistic measurements.  Next steps A geostationary satellite positioned at about 22,000 miles above the equator will orbit in sync with the Earth’s rotation, thus remaining fixed above the same region. Measurements by the satellite's instruments can be taken many times a day. A constellation of such satellites would provide the coverage over populated regions needed to provide enough data to analyze air quality and atmospheric composition, determine whether the pollution is human-made or natural, and track its movement. In addition to carbon monoxide, instruments on these satellites would gather data on other pollutants, such as nitrogen dioxide and ozone. "Combined, those will give you good indications of the chemical conditions of the atmosphere," Barre said. That would enable scientists to track pollutants both vertically and horizontally in our atmosphere, he said, and that is "what's really needed to monitor, forecast, and manage air quality on a daily basis." About the article Jerome Barre, David P. Edwards, Helen M. Worden, Arlindo Da Silva, and William Lahoz, 2015: On the feasibility of monitoring carbon monoxide in the lower troposphere from a constellation of Northern Hemisphere geostationary satellites. (Part 1). Atmospheric Environment, 113, 63-77, doi:10.1016/j.atmosenv.2015.04.069 Writer/ContactJeff Smith, Science Writer and Public Information Officer Collaborating organizations NASA Norwegian Institute for Air Research FundersNational Science FoundationNASA

What's driving soot across India?

October 12, 2015 | As a teenager in the 1990s, NCAR postdoctoral scientist Rajesh Kumar bicycled five miles from his village north of Delhi to school. He remembers riding through clear skies and fog, but not smog. Today, Delhi ranks as the most polluted city in the world with 12 additional Indian cities in the notorious top 20, according to the urban air database released last year by the World Health Organization. In Delhi alone, small particulates averaged six times the recommended maximum, a hazard to the health especially of children and the elderly. Smog also contributes to climate change by trapping heat that otherwise would escape the atmosphere. Scientists have identified the sources and transport patterns of black carbon soot, a health and visibility problem for a dozen Indian cities, including Delhi, shown here enveloped in smog. (Photo by Jean-Etienne Minh-Duy Poirrier, Creative Commons [CC BY-SA 2.0], via Flickr.) Experiencing increased air pollution in his home country has inspired Kumar to understand more about its driving forces and remedies. Most recently, the researcher was lead author on a paper concluding that black carbon emissions—fine particles or soot caused by the incomplete burning of fossil fuels and biomass from plant or animal waste—are transported in the atmosphere across India. Only 5 percent of the emissions at any given time blow in from outside the country.   Black carbon emissions from northern India, for example, contribute up to 30 percent to black carbon pollution in southern India during the winter, the study found, while southern India makes a similar contribution to northern India during the summer monsoon season. While human activity—agricultural waste burning, use of household cook stoves, industry and vehicles—is the cause of most black carbon emissions, the seasonal cycle is driven by the monsoon weather. "What this means is that India has the power to reduce black carbon emissions significantly—but only if individual states and regions work together on mitigation strategies," said Kumar. The paper appears in the Journal of Geophysical Research – Atmospheres. A research team headed by Kumar now is conducting a simulation of how air quality is likely to change in South Asia overall by mid-century, a topic he will discuss at the American Geophysical Union’s fall meeting in December. Haze from urban and industrial pollution, as well as agricultural and wildland fires (red dots), can be seen over northern India below the Himalayan mountain range in this satellite image from October 2014. (Photo courtesy NASA.) Shining a spotlight on soot Co-author Mary Barth, an NCAR scientist, noted that attention to black carbon emissions has grown as more is known about its ability to strongly absorb solar radiation. The issue is especially of concern in densely populated areas such as the Indo-Gangetic Plain, which consists of Bangladesh and swaths of India and Pakistan. There is concern not only due to black carbon's atmospheric impacts, but also because soot that settles on snow absorbs more heat from the Sun and thus accelerates melting. Emission levels are so high in that region that there is concern about glacier melt in the Himalayas—the region's primary storehouse of water. "If you curtail black carbon emissions, you can reduce heat over the short term," Barth said. "It's something you can do while working to reduce carbon dioxide levels in the atmosphere." Black carbon has a short life span of only a week or two, while carbon dioxide molecules remain in the atmosphere for about 100 years. Prior studies have provided important information about black carbon pollution in parts of India, but they didn't detail the specifics of how the particles are transported across the country. For their observational database, the research team used monthly average black carbon concentrations reported from 21 sites representing a range of environments, including cities, semi-urban areas, and coastal areas. They also took meteorological data into account. The team then developed models for tracking air pollutants that were combined with the NCAR-based Weather Research and Forecasting Model. NCAR researcher Rajesh Kumar studies black carbon emission levels. (©UCAR. Photo by Carlye Calvin. This image is freely available for media & nonprofit use. While the computer model reproduced the seasonal cycle of black carbon emissions fairly well, it was more difficult to capture that seasonality in the complex terrain of the Himalayan region. Kumar, who also has studied the impact of ozone pollution on India's agriculture production, notes that India is taking steps to improve its air quality. Efforts include national programs to promote liquefied petroleum gas for cooking and solar power for energy production and irrigation. "I hope that in 20 years or so, India will be able to talk about its good air quality, not its pollution," Kumar said.  About the article Rajesh Kumar, M. C. Barth, G. G. Pfister, V. S. Nair, Sachin D. Ghude, and N. Ojha, 2015: What controls the seasonal cycle of black carbon aerosols in India? Journal of Geophysical Research - Atmospheres, 120, 7788-7812, DOI: 10.1002/2015JD023298 | OpenSky Dive Deeper Variability in emission levels was simulated by applying a tagging technique developed by Kumar. The technique consists of assigning 10 different values or "tracers" to standard black carbon particles in order to track the emissions from different regions and sources. For example, separate tracers were assigned to emissions from four regions of India and from outside the country to determine geographic variability. Traditionally, researchers would have done a separate simulation for each tracer, or variable. Putting all 10 tracers in the model at the same time saved a tremendous amount of computing time, Kumar said. The data, crunched by the NCAR-Wyoming Supercomputing Center's Yellowstone system, took only about a tenth the time of the traditional method. Writer/contact Jeff Smith, Science Writer and Public Information Officer Collaborating organizations Indian Institute of Tropical Meteorology Max Planck Institute for Chemistry, Germany Vikram Sarabhai Space Center, India. Funder National Science Foundation


Subscribe to Air Quality & Pollution