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Clarissa Roman was born and raised in Reno, Nevada. She has experienced firsthand the impacts of wildfire smoke, both on herself as well as her young niece. Clarissa takes action by working with schoolchildren in Reno to teach them what they can do to fight climate change.

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Youth Climate Story: Wildfires and Air Pollution in Nevada

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Clarissa Roman was born and raised in Reno, Nevada. She has experienced firsthand the impacts of wildfire smoke, both on herself as well as her young niece. Clarissa takes action by working with schoolchildren in Reno to teach them what they can do to fight climate change.

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Climate Change and the Australia Wildfires

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Climate Change and the Australia Wildfires

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Alliance for Climate Education | 2020

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Climate Change and the Australia Wildfires

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NASA

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The effects of forest fires show up in a multi-satellite view of pollution.

By Natasha Vizcarra

On the tail of three scorching heat waves in the summer of 2007, massive forest fires broke out across Greece and destroyed thousands of acres of forest, olive groves, and farmland. Heavy plumes of smoke billowed from burning forest canopies, and ash from the fires dusted ancient and modern buildings in nearby cities and towns. Numbering 3,000 from June to early September, the fires were the worst that Greece had seen in fifty years.

Athens is already one of the most polluted cities in Europe, more so in the summer when humidity and the intense Mediterranean sun heat up industrial and vehicular pollutants lingering in the atmosphere. Did the forest fires cause the city's air pollution levels to get worse? Researchers in Greece could not answer this question easily. Most of the fires burned in rural areas where there were no ground-based instruments to measure pollution. The fires also produced gigantic smoke plumes that blew hundreds of miles from inland, across coastlines, and on to the Ionian Sea. These plumes were difficult to study using available ground monitoring networks alone.

A man walks through the Acropolis while smoke plumes billow from a forest fire near Athens on July 25, 2007. More than 3,000 forest fires burned in Greece that summer, mostly in areas where there were no ground instruments to observe the impact of the smoke on air quality. (Courtesy V. Berger)

The Greek government turned to the Harvard School of Public Health for help. Yang Liu studies air quality using remote sensing data and was a research associate there at the time of the Greek fires. He said, "The best tool was satellite remote sensing. We happened to have cloud-free days during most of the fire episodes, and that was ideal for satellites to observe the transport and the evolution of those plumes." Liu, now an assistant professor at Emory University's Rollins School of Public Health, knew that satellite sensors were a fairly new information source for air pollution studies. But he suspected that the right combination of satellite sensors could reveal how the forest fires affected Athens' already fragile air quality.

Two pollution spikes

Pollution peaked twice in the Athens area during the last week of August and the first week of September. From August 24 to 28 and then again from August 30 to September 3, the average concentration of air particles in Athens reached a density of nearly 100 micrograms per cubic meter. These measurements were far above the European Union Ambient Air Quality Standard of fifty micrograms per cubic meter. "We wanted to know if some or all of these pollution peaks were caused by the fire plumes," Liu said.

To find out if the pollution episodes could be traced to the fires, Liu first needed to know if smoke plumes from the fires had drifted to Athens. Liu checked for smoke plumes using true-color satellite images of Athens and the vicinity from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA's Terra and Aqua satellites.

Smoke from forest fires in Greece on August 25, 2007, is evident in this satellite image from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. The active forest fires, outlined in red, occurred in the Peloponnese and Attica regions, and on the island of Evia. Long-range smoke plumes from Evia extend west over the city of Athens toward the Ionian Sea. (Courtesy MODIS Rapid Response Project, NASA Goddard Space Flight Center)

He determined plume height and direction by using numerical weather models, and then validated the information with data from the Multi-Angle Imaging Spectroradiometer (MISR) sensor on NASA's Terra satellite, available from NASA's Atmospheric Science Data Center (ASDC). Ralph Kahn, a senior research scientist at NASA's Goddard Space Flight Center, worked with Liu on the study. He said, "Plume height is important. How high the smoke is injected into the atmosphere by the fire determines how far the smoke particles travel from these fires, in which direction they travel, and how long they stay in the atmosphere. Numerical weather models complement the snapshots from MISR and MODIS, filling in what the polar-orbiting satellite instruments miss."

During the first pollution episode, MODIS true-color images showed smoke plumes southwest of Athens in the Peloponnese region, and northwest in the country of Albania. MODIS also detected fire spots on the island of Evia, northeast of Athens, and in nearby forested areas northwest of the city. MISR detected plume heights from the Peloponnese fires that were 2.5 kilometers (1.6 miles) high. But weather and wind data showed that a southwesterly wind blew the smoke plume away from Athens and into the Ionian Sea. The same wind blew the smoke plumes from the Evia Island fires right into the city. Liu said, "As a result, the Evia fire is probably a major contributor to increased pollution in Athens during this period." In the second episode, MODIS only detected minor fire spots in the Peloponnese region, and several fire spots in Albania. MISR detected no major smoke plumes.

With two very different pollution episodes, the first with smoke plumes blowing into Athens from Evia, and the second without any dominant smoke plume blowing into the city, Liu and Kahn then needed to figure out what quantities of aerosols-tiny particles of solid or liquid suspended in the air-were present in the atmosphere. They also needed to find out what kinds of aerosols were hovering over the city.

Smoke obscures the midday Athens sky in this August 25, 2007, photo. A portion of the forest on Mount Hymettus was burning. (Courtesy A. Babili)

Slicing through smoke

To observe aerosol abundance, Liu and Kahn needed an instrument that could observe huge areas, such as the length and breadth of the Peloponnese smoke plume. They used total column aerosol optical depth (AOD) data from MODIS, distributed by NASA's Level 1 Atmosphere Archive and Distribution System Distributed Active Archive Center (LAADS DAAC). Kahn said, "MODIS was the ideal instrument because it has a swath of 2,300 kilometers [1,400 miles] and observes the entire Earth at least once in two days." Liu superimposed these data over MODIS true-color images of the fire sites during the two episodes, and used this combination to determine pollution intensity and source location. The MODIS AOD data confirmed what the weather and plume height observations suggested for the first pollution peak: that smoke from Evia had blown into Athens, and residual, circling smoke from the Peloponnese region drifted into Athens from the south toward the end of the period. MODIS AOD data for the second episode showed that aerosol abundance was higher in Athens than in surrounding areas.

At this point, it seemed clear that smoke from the forest fires might not have affected Athens during the second pollution episode. But were the fires responsible for the first one? To answer this question, Liu and Kahn needed to know what kinds of aerosols were present in Athens during the two periods. They used data from the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite, archived at NASA's Goddard Earth Sciences Data and Information Services Center (GES DISC), and aerosol type data from ground instruments. Kahn said, "OMI can distinguish particles by the way they reflect light back into the sensor. This tells something about what the particles are made of, and gives us clues to where they come from. We also added ground-based measurements to the mix because they are much more precise." Liu and Kahn's colleagues-Archontoula Chaloulakou, at the National Technical University of Athens, and Petros Koutrakis, at the Harvard School of Public Health-provided the ground instrument data.

A forest fire burns on the island of Zakynthos in Greece on the evening of July 25, 2007. Heat waves, a strong wind, and arson caused many fires in Greece that summer, adding smoke plumes to an already polluted skyline. (Courtesy C. Osbourn)

What Liu and Kahn found out surprised them. The combination of aerosol type data showed that during the first episode, the average pollution contribution from forest fires was 28 micrograms per cubic meter, but pollution from traffic emissions and other sources was 33 micrograms per cubic meter. During the second episode, forest fires contributed an average of 17 micrograms per cubic meter, but traffic emissions contributed 48 micrograms per cubic meter. Liu said, "Fire plumes contributed aerosols more significantly to the pollution spike in the first episode, and to a lesser extent in the second episode. But during both episodes, emissions from vehicles in Athens still dominated the aerosol composition."

Smog versus smoke

To Liu and Kahn, the results were consistent with what researchers have observed in other countries. Liu said, "Even during the height of the forest fires, local traffic remained the number one contributor to air pollution levels. In Athens, as in many cities all over the word, the major contributor to air pollution is still vehicular traffic."

The use of multiple remote sensing instruments helped paint a more detailed picture of the forest fires' impact on the air quality in Athens. "Multiple instruments tell a better and more complete story than any individual instrument can, and they also cross-validate each other," Liu said. Kahn agree, saying, "We have the tools. In situ air quality measurements are made routinely from the surface. But combining them with satellite data gives you a much broader perspective."

These images, from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua and Terra satellites, show total column aerosol optical depth (AOD) overlaid on MODIS true color images. The images reveal a concentration of aerosols from the island of Evia drifting to Athens on August 25, and another concentration of aerosols drifting into the city from the Peloponnese region on August 27. Black polygons represent fire spots, and the purple star represents the city of Athens. Orange and red indicate higher aerosol levels, while blue and green indicate lower levels. (Courtesy Y. Liu)

Liu and Kahn even discovered new possibilities for one sensor. Liu said, "It's interesting to note that MODIS behaved very well during the two episodes. It tracks ground level pollution very well." MODIS works best when the pollution is sulfate-dominated, the kind that comes from industrial sites. But during the two pollution peaks, pollution was dominated by motor vehicle emissions. "In our two episodes, pollution was composed of nitrate, black carbon, and organic carbon. But the MODIS instrument still worked very well," Liu said.

Remote sensing is proving to be an important tool in monitoring air quality in major urban areas worldwide. Liu said, "We are entering the age of air quality monitoring from space. Carefully interpreted satellite data can give us valuable information about air pollution conditions and forest fire episodes. Although still at its infancy, satellite-based air quality monitoring has started to provide early warnings of pollution events to major urban areas all over the world."

References

Liu, Y., R. Kahn, A. Chaloulakou, and P. Koutrakis. 2009. Analysis of the impact of the forest fires in August 2007 on air quality of Athens using multi-sensor aerosol remote sensing data, meteorology, and surface observations. Atmospheric Environment, doi: 10.1016/j.atmosenv.2009.04.010.

Yang Liu, interview by Lindsay Patterson, Earth sky: A clear voice for science. November 25, 2008. https://earthsky.org/human-world/yang-liu-at-the-intersections-of-air-pollution-and-public-health

For more information

NASA Atmospheric Science Data Center ( ASDC)

Moderate Resolution Imaging Spectroradiometer ( MODIS)

MODIS Rapid Response System

Multi-angle Imaging SpectroRadiometer ( MISR)

Ozone Mapping Instrument ( OMI)

About the remote sensing data

Sensors

Moderate Resolution Imaging Spectroradiometer (MODIS)

Multi-angle Imaging SpectroRadiometer (MISR)

Ozone Mapping Instrument (OMI)

Data sets

MODIS Level 2 Aerosol

MISR Level 2 Products

Near-UV Aerosol Optical Depth and Single Scattering Albedo

Resolution

10 kilometer, derived from Level 1 radiance data at 0.5 and 1.0 kilometer

1.1 kilometer

13 x 24 kilometer nominal resolution at nadir

Parameters

Aerosol optical depth

Stereo height

Aerosol index and associated aerosol types

DAACs

NASA Level-1 and Atmosphere Archive and Distribution System Distributed Active Archive Center ( LAADS DAAC)

NASA Atmospheric Science Data Center ( ASDC)

NASA Goddard Earth Sciences Data and Information Services Center ( GES DISC)

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The effects of forest fires show up in a multi-satellite view of pollution. By Natasha Vizcarra On the tail of three scorching heat waves in the summer of 2007, massive forest fires broke out across Greece and destroyed thousands of acres of forest, olive groves, and farmland.

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Snowfall over the weekend gave firefighters in Colorado some some desperately needed relief as they worked to contain the two largest blazes in state history burning just ten miles apart. The cold snowy weather helped limit the growth of the infernos, but it also prevented fire crews from making progress in containing them.

The Cameron Peak Fire near Rocky Mountain National Park is now the largest wildfire in Colorado history, at almost 208,000 acres in size. The fire was 64 percent contained as of Monday morning.

It's followed closely by the East Troublesome Fire to its southwest, which has now burned more than 192,000 acres and was 10 percent contained as of Monday. The blaze stunned forecasters last week when, over a period of 24 hours, it grew six times in size to more than 125,000 acres. The fire is burning at an elevation of 9,000 feet and across both sides of the continental divide. forced Rocky Mountain National Park to close. It's now the second-largest fire in Colorado history.

The previous record-holder before Cameron Peak was the 137,000-acre Pine Gulch Fire near Grand Junction, Colorado. That fire also ignited this year and was declared 100 percent contained in September. It only held on to its record as Colorado's largest wildfire for seven weeks. Three of the four largest wildfires in state history have ignited just since July.

Smaller blazes this year have set records too. The CalWood Fire became the largest wildfire in the history of Boulder County after igniting earlier this month. The fire burned 10,000 acres and was 76 percent contained by Monday.

Beyond the threat from the flames, these various wildfires have sent dangerous, smoky air into cities like Denver and Fort Collins, triggering air quality alerts off and on for months. The smoke from Colorado's wildfires has even reached Europe.

Together, the recent blazes in Colorado add up to an unusually long, late, and severe wildfire season, and it's not likely to let up anytime soon. "The current fire season, it's definitely a crazy one," said Chad Hoffman, an associate professor of fire science at Colorado State University. "We still have dry, windy conditions pushing these fires."

Some unique weather conditions this year set the stage for Colorado's blazes, but the threat from wildfires is growing across the state due to human development and climate change.

What's fueling Colorado's fires this year

It's an increasingly familiar story. Like the epic wildfires this year across California, Oregon, and Washington, the wildfires in Colorado arose amid a year of extreme heat and dryness.

Heat waves baked the state this summer and persisted into the fall. The high temperatures increased the evaporation of moisture from vegetation, leaving plants dry and ready to burn. There was also less rainfall. Over the past month, precipitation was less than 10 percent of what is typical.

"By the end of September, nearly 100% of the state was experiencing some level of drought, up from 51% since the beginning of the calendar year," according to the Colorado Climate Center's Monthly State of the Climate report. The state is on track to have its second-driest year on record.

That aridity has left almost every type of vegetation in the state primed to burn, as was evident in the Cameron Peak Fire. "It burned all the way from fir forest, ponderosa pine, mixed conifer. It's burned through some grasslands and shrublands as well," Hoffman said. "It's burned through areas that have previously burned, like during the Bobcat Fire. It's burned through bark-beetle-affected areas. So a really big mix of fuels that this fire has burned through over the last 60 days."

It's also uncommon to see fires this late in the year in Colorado. Typically, winter precipitation starts to set in and cap fire seasons in the autumn.

This fits within the trend of fire seasons in Colorado getting longer. Wildfires are a natural part of the landscape in the state, as they are in places farther west. Many woodlands have evolved to deal with and benefit from periodic fires.

However, humans have been making fire risks worse. That's in part due to climate change, which is changing weather patterns and driving some of the aridity in Colorado's forests.

"Our 2020 wildfire season is showing us that climate change is here and now in Colorado," said Jennifer Balch, director of the Earth Lab and an associate professor of geography at the University of Colorado Boulder, in an email. "Warming is setting the stage for a lot of burning across an extended fire season."

In particular, there has been a growth in late-season fires in Colorado. The area burned by October fires over the past decade has tripled compared to the area burned between 1980 and 2000. "We do see fall fire events in Colorado, related to fast, downslope winds. But to see multiple events start this late, in the middle of October, is very rare," Balch said.

It's also a function of more people living in high-risk areas. "The growing population in Colorado means we have more people in the woods, which leads potentially to more ignitions," Hoffman said. The vast majority of wildfires in the United States have human causes, though in Colorado about half of fires in the state are ignited by lightning strikes.

The growing fire risk is also a consequence of more than a century of suppression of natural wildfires. By putting out blazes, vegetation in the state has accumulated, so during periods of extreme dryness, there is much more fuel to burn than there would be had more fires been allowed to proceed.

There are now efforts to reintroduce fire to the landscape, but vast swaths of the state need fuel reduction treatments, and the window for safely conducting measures like prescribed burns is shrinking as the climate warms.

"We love our beautiful mountain landscapes to live and to recreate," Balch said. "But these beautiful landscapes are also flammable, and more flammable with climate change. We need proactive solutions that manage our fuels in places where it matters most for ecosystems and people."
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Colorado is fighting its largest wildfire in history. Other massive blazes are close behind.

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Snowfall over the weekend gave firefighters in Colorado some some desperately needed relief as they worked to contain the two largest blazes in state history burning just ten miles apart. The cold snowy weather helped limit the growth of the infernos, but it also prevented fire crews from making progress in containing them.