aerosols – Page 2 – What On Earth

Why Cutting Black Carbon Emissions May Save Arctic Sea Ice

Arctic sea ice is retreating at an unexpectedly rapid pace. Average ice extent in September has declined by 11.5 percent per decade relative to the 1979 to 2000 average, according to satellite measurements of the ice. Many climatologists expect that the Arctic will be ice-free during the summer in as few as thirty years if current trends continue.

Most scientists who study the issue closely agree that reducing carbon dioxide emissions is the key to stabilizing Earth’s climate. However, even if nations began curbing emissions immediately the world would continue to warm for many decades. While Earth can reabsorb some portion of carbon dioxide emissions fairly rapidly, a significant amount of carbon will remain in the atmosphere for long periods. Some 20 percent of carbon dioxide emissions are expected to remain in the atmosphere for tens of thousands of years, according to some estimates.

That doesn’t bode well for the dwindling Arctic sea ice.

However, if Mark Jacobson, an atmospheric scientist from Stanford University is right, there may still be hope for Arctic sea ice and the ecosystem it supports. Jacobson studies the climate effects of tiny airborne particles called black carbon, a scientific term for soot, the black stuff in smoke. Wood, dried animal dung, and other biofuels all produce black carbon when burned. And fossil fuels, such as coal and petroleum, are especially prolific producers of the particles.

Under a microscope, black carbon is an amorphously-shaped particle with a branching globular shape. What’s most notable about black carbon, however, is the many ways that it can warm the climate. Black carbon particles, which unsurprisingly tend to be a coal black color, warm the air directly by absorbing sunlight and converting it into infrared radiation. They also reduce the reflectivity of the surface when deposited on icy surfaces. And they infiltrate cloud droplets in ways that can cause clouds to dissipate more quickly than they otherwise might.

Together such effects can produce a potent warming effect. Last week, during a session focused on black carbon at the American Geophysical Union meeting in San Francisco, Jacobson reminded meeting attendees of a bit of news that Stanford released a few months back. Reducing soot emissions may be the fastest method – indeed the only way — of saving the Arctic ice, Jacobson noted. “On average black carbon particles stay in the air for just four or five days, so reducing emissions has an immediate impact,” he said in an interview later. “That’s not the case for greenhouse gases.”

Recent modeling, conducted by Jacobson and funded in-part by NASA, suggests that eliminating soot emissions from fossil fuel and biofuel burning over the next fifteen years could reduce Arctic warming by up to 1.7 °C (3 °F). Net warming in the Arctic, in comparison, has been about 2.5 °C (4.5 °F) over the last century.

–Adam Voiland, NASA’s Earth Science News Team

Speaking of Contrails…

The prospect of a renegade missile transfixed newscasters last week after a videographer captured imagery of an unusual contrail near the coast of California. The now notorious plume initially baffled commentators as it seemed to point vertically into space and appeared larger than a standard airplane contrail.

The reality, which trickled out in the days following the uproar, turned out to be far less dramatic than some of the more inventive theories circulating. Most experts now say the mysterious plume was the product of a jet. The time of day and the particular trajectory of the jet conspired to create the illusion.

Sure, it might seem like a letdown, but here at What on Earth we would argue that jet contrails are perfectly fascinating in their own right. Where on Earth do they come from? The cirrus-cloud like condensation trails form when water vapor condenses and freezes around tiny airborne particles called aerosols that spill from jet engines.

NASA Langley Research Center, in Hampton, Va., hosts a thorough website that’s well-worth a look for those who happen to be contrail-curious. Langley points out, for example, that contrails are hardly monolithic, noting that there are actually three major varieties of contrails: short-lived, persistent, and persistent spreading. Here’s how Langley describes the three types:

Short-lived contrails look like short white lines following along behind the plane, disappearing almost as fast as the airplane goes across the sky, perhaps lasting only a few minutes or less. The air that the airplane is passing through is somewhat moist, and there is only a small amount of water vapor available to form a contrail. The ice particles that do form quickly return again to a vapor state.

Persistent (non-spreading) contrails look like long white lines that remain visible after the airplane has disappeared. This shows that the air where the airplane is flying is quite humid, and there is a large amount of water vapor available to form a contrail. Persistent contrails can be further divided into two classes: those that spread and those that don’t. Persistent contrails look like long, narrow white pencil-lines across the sky.

Persistent spreading contrails look like long, broad, fuzzy white lines. This is the type most likely to affect climate because they cover a larger area and last longer than short-lived or persistent contrails.

Meanwhile, Our Changing Planet, a book co-edited by a number of NASA scientists that offers a good overview of remote sensing, devotes a chapter to climate impacts of the ubiquitous artificial clouds. Via Our Changing Planet:

Persistent contrails also play a role in climate because they reflect sunlight and trap infrared radiation just like their naturally formed cousins. Thus, the presence of a contrail cluster in an otherwise clear sky can diminish the amount of solar energy reaching the surface during the daytime and increase the amount of infrared radiation absorbed in the atmosphere at all times of day. Currently, the overall impact appears to be a warming effect, but research is continuing to unravel the role of this phenomenon in climate change.

Another interesting tidbit from Our Changing Planet:

Persistent contrails can often grow into natural-looking cirrus clouds within a few hours, a phenomenon that is best observed from space. Although they typically last for only 4-6 hours, some clusters have been observed to last more than 14 hours and travel thousands of kilometers before dissipating. These persistent contrails are estimated to have caused cirrus cloud cover to rise by three percent between 1971 and 1996 over the United States and are well-correlated with rising temperatures, though not the only cause of them. Increasing traffic in nearly every country of the world will cause a rise in global cirrus coverage unless the upper troposphere dries out or advances in air traffic management and weather forecasting or in aircraft propulsion systems can be used to minimized contrail formation.

Indeed. Take a look at this mesmerizing data visualization of just a mere day of air traffic…

–Adam Voiland, NASA’s Earth Science News Team

Photo above of contrails in a star pattern by John Pertig, courtesy of NASA Langley Research Center.

Volcano Music

What on Earth was that sound? Was it a bird? A plane? A humpbacked whale?

No, it was fiercely hot gas whooshing through the guts of a volcano — Arenal Volcano in Costa Rica, to be precise. Milton Garces, the director of the Infrasound Laboratory at the University of Hawaii, Manoa, recorded the sound clip we posted last week.

Garces explains the phenomenon this way:

“Much like human voicings are defined by the combination of air flow through the vocal chords, tract, and mouth shapes, this harmonic tremor sound is shaped by the interaction of volcanic gases as they are released and flow through open conduits.”

NASA satellites have got Earth’s volcanoes covered from orbit. They provide round-the-clock monitoring of volcanic eruptions in progress or those possibly on the way. Just two of the satellites used to monitor volcanic activity are Aqua (with its MODIS instrument) and Terra (with its ASTER instrument).

Volcanologists use the satellite data from NASA’s fleet to detect heat and telltale volcanic gases emanating from volcanic vents. Also, Global Positioning System satellite devices allow researchers to gauge subtle changes in the land surface near volcanoes.

And once a volcano pops off, NASA satellites track drifting ash clouds that could threaten aircraft. (You may recall the shenanigans of a certain unpronounceable Icelandic volcano, Eyjafjallajökull, earlier this year.)

As the NASA birds pass silently overhead, Garces clambers up live volcanoes to record their subterranean rumblings. He uses the sounds to diagnose the physical status of volcanic plumbing systems – for example, whether they might be recharging with molten rock (magma) and getting ready to erupt.

These very low frequency waves are called infrasound. In fact, they are too low in their raw form to be audible to humans. So Garces speeds them up artificially to a frequency range the human hearing can detect. Here’s how he explained it to us:

“This signal, which has been sped up by a factor a hundred to make it audible, in reality has a dominant periodicity of about 1 cycle per second (1 Hz). In the field, it sounds like a chugging sound with 1 s puffs, and it is not tonal at all. We lose our sense of tonality at frequencies below around 16 Hz, so infrasound, however harmonious, will be perceived by us more like a beat than a tune.”

In other words, volcano infrasound is pretty interesting to a scientist, but you can’t dance to it — or at least it would be the ultimate slow dance.

— Daniel Pendick, Geeked on Goddard; Eyjafjallajokull image courtesy of NASA Goddard’s MODIS Rapid Response Team

Massive Air Pollution Event Highlights Sulfur Dioxide Trends in China

This spectacular cloud of smog and haze formed over eastern China last week when a high-pressure weather system moved in to the area, allowing industrial and burning byproducts to settle with little disturbance from winds. As NASA’s Earth Observatory reported, NASA satellite instruments detected extremely high levels of sulfur dioxide, which most likely came from various industrial processes such as coal-burning power plants and smelters (facilities that melt or fuse ores in order to extract usable metals).

Satellites also detected high levels of aerosols — most likely sooty black carbon or organic carbon particles from wildfires and fossil fuel burning – that absorb sunlight and “trap” heat. In fact, the air was so thick with the light-absorbing particles at times that seeing the midday sun clearly would have been difficult. Bearing this out, news media reported numerous traffic accidents associated with the lack of visibility.

How does this event fit into broader pollution trends in the region? A study published earlier this year in Atmospheric Chemistry and Physics offers some insight. The authors, which included a researcher from Goddard Space Flight Center, analyzed sulfur dioxide emission trends in China since 2000 and made a number of notable observations. These included:

From 2000 to 2006, total sulfur dioxide emissions in China increased by 53 percent from 21.7 teragrams to 33.2 teragrams, an annual growth rate of 7.3 percent per year.
Geographically, emissions from northern China increased by 85 percent whereas emissions from the south increased by only 28 percent.
However, emissions started to decline in 2006, primarily due to the wide application of flue-gas desulfurization (FGD) devices in power plants.

Want more details? You can read the full paper here [PDF].

–Adam Voiland, NASA’s Earth Science News Team, Image courtesy of NASA’s Earth Observatory

Glory Versus the Curse of the Black Carbon

Kick back, make yourself some popcorn, and enjoy one of the latest offerings from NASA Television: a tongue-in-cheek trailer about the horrors of airborne particles called aerosols. Black carbon plays the villain, and it’s this sooty particle (which comes from wildfires, campfires, various industrial processes, and diesel fumes) that gets the blame for “cursing” atmospheric scientists with a “scourge of ignorance”.

Plenty of specialists here at Goddard Space Flight Center will tell you that, over the years, we’re making real progress understanding aerosols, but there’s little doubt that the tiny airborne droplets and particles have given climatologists headaches over the years.

Back in March of 2009, James Hansen, director of the Goddard Institute for Space Studies, laid out the key obstacles underpinning what he called the “Nasty Aerosol Problem” in a presentation he gave in Copenhagen. As he puts it in one slide:

* “We do not have measurements of aerosols going back to the 1800s – we don’t even have global measurements today.

* Any measurements that exist incorporate both forcing and feedback.

* Aerosol effects on clouds are very uncertain.”

NASA’s upcoming Glory mission, which carries a promising new gizmo for studying aerosols called the Aerosol Polarimetery Sensor (APS), looks to be our next best shot for getting a better handle on the problematic particles. Glory is hardly the only NASA effort addressing aerosols, but I’ve certainly noticed that nothing rivals a satellite mission (as opposed to, say, ground or aircraft campaigns) when it comes to generating buzz in the hallways.

You can learn more about Glory here, here, and here. And why not follow Glory on Twitter or Facebook?

–Adam Voiland, NASA’s Earth Science News Team

Behind the Scenes With Scientists Who Created A Global Air Pollution Map

Yesterday, NASA posted an article about a new global map of health-sapping PM2.5 air pollution. The Dalhousie University researchers who made the map used data from NASA’s MISR and MODIS satellite instruments, as well as information from a computer model called GEOS-Chem. You can read the news story here (or the accounts from Wired, Public Radio, and UPI), but we also wanted to share some of the audio from our interview with the scientists for those who want more details. The scientists being interviewed are Aaron van Donkelaar and Randall Martin; the person asking the question is Goddard-based science writer Adam Voiland.

What was the most interesting thing you found from this analysis?

Why go to the trouble of making this map?

What’s the heavy band of particulate matter in Africa? Is dust bad for our health?

Martin: There’s no lower bound on health effects

Have other researchers done this kind of analysis?

Are these data ready for prime time?

How did you combine data from both satellite instruments?

–Adam Voiland, NASA’s Earth Science News Team

4 Views of Eyjafjallajökull’s Plume That You Probably Haven’t Seen Before

When the volcano roared to life and began spewing huge amounts of ash and gas into the atmosphere, Eyjafjallajökull’s giant plume stranded millions of travelers and captivated the rest of us as it wafted away from Iceland.

Most images have shown how the plume might appear to a human from space. But to an aerosol scientist, the real excitement comes from the instruments that produce less recognizable images that nevertheless reveal subtle details about the nature of the plume.

One instrument or one satellite alone is not likely to yield breakthrough insights about volcanic plumes. Rather, constant comparisons between numerous sets of data—collected by a variety of satellite, aircraft, and ground-based platforms—are most likely to lead to new discoveries.

With that in mind, aerosol scientists from NASA’s Goddard Space Flight Center and neighboring institutions met last month at a special AEROCENTER seminar to share information about some aspects of Eyjafjallajökull’s plume that they’ve studied so far.

Such cross-satellite and cross-platform efforts make it possible to address some of the thorniest problems in the field. Comparing results from several instruments, for example, makes it easier to understand the dispersion of plumes and—with the help of computer models—predict how plumes might behave, noted Santiago Gassó, the Goddard geophysicist who organized the seminar.

Though the scientists have just started picking their way through Eyjafjallajökull data, there are a number of presentations from the meeting to click through if you’re interested. There’s nothing Earth-shattering to report yet, but we did find some views of the plume that you likely haven’t seen in the newspapers. You can find more imagery of Eyjafjallajökull’s eruptionand plume here,here, here, here, here, here, and here.

MISR – Plume Height

NASA scientists used an instrument called MISR aboard the Terra satellite to view the ash plume from multiple angles, and then applied a stereo-imaging technique to derive the height of the ash cloud at different points during the eruption. The result is the colorful image on the right that distinguishes plume height with bright reds (6 km), oranges (5 km), yellows (4 km), greens (3 km), and blues (2 km). The blue, near-surface part of the plume is resuspended ash. (Image Credit: NASA/JPL/MISR)

CALIPSO – Vertical Profile

The CALIPSO satellite provides a vertical profile of a whole slice of the atmosphere with a LIDAR instrument that shoots laser pulses at the atmosphere below and measures how it reflects off particles in the atmosphere. In this image, captured on April 17 as the satellite passed over France, the plume appears as a wispy band of yellow and red. The thick yellow layer below is air pollution hovering near the surface of France. (Image Credit: NASA/CALIPSO/Winker)

OMI – Sulfur Dioxide (SO₂)

The Ozone Monitoring Instrument (OMI) aboard NASA’s Aura satellite had eyes for ash as well as something that’s invisible to the human eye: the transparent (and toxic) gas sulfur dioxide (SO₂). OMI observed sulfur dioxide billowing out of the volcano at a clip of as much as 10 thousand tons a day. The OMI instrument produced this image, which shows higher concentrations of sulfur dioxide in red and lower concentrations in blue and purple, on April 30—two weeks after the peak of Eyjafjallajökull’s eruption between April 14 and 17. (Image Credit: NASA/OMI/via Joiner)

DLR Falcon – Aircraft LIDAR

A few days after the eruption began, European scientists scrambled a DLR Falcon jet equipped with a LIDAR and other instruments. The LIDAR, cruising at 8 km altitude, detected volcanic ash in the altitude range of 3.5 km to 5.5 km. The ash plume appears as a yellow and green mass above a layer of clouds (seen as the line of rust-colored spots beneath the ash). When the instrument collected this data, the ash had aged four or five days. The white streaks on the image represent areas where the LIDAR did not detect a significant amount of aerosol. (Image Credit: DLR/via Diehl)

— Adam Voiland, NASA’s Earth Science News Team

Fun with Aureoles and Aerosols

Credit: Earth Science Picture of the Day/Rob Rathkowski

Earth Science Picture of the Day (EPOD) recently ran a series of photos that illustrates nicely the impact that small airborne particles called aerosols can have on light.

As EPOD notes , the size of an aureole — the halo-like circle that appears around the sun when viewed through a haze or mist — depends on the amount of aerosol in the air. More aerosols mean more light is scattered, which produces larger aureole). Since most aerosols are concentrated near Earth’s surface, the aureole at sea level appears much larger than it would high on a mountain peak. You can try this experiment yourself to get a sense of the aerosol load in the air you’re breathing.

Aerosols are a major preoccupation for climate scientists as the particles—including dust, ash, sea salt, soot, and industrial pollutants—can scatter light and affect Earth’s energy balance. Infusions of ash and sulfate from volcanic eruptions, for example, are capable of cooling global temperatures by 0.3 degrees Celsius. Likewise, sulfate aerosols from factories and power plants can mask global warming somewhat and are often bandied around as possible components of geoengineering schemes.

Want to learn more about how aerosols scatter light? EPOD has another post on the topic that compares aureoles at sunsets in the Netherlands before (below left) and after (below right) the arrival of a massive volcanic ash cloud from the eruption of Eyjafjallajökull. Also, for optics aficionados, a site called Atmospheric Optics will walk you through a number of interesting examples of aerosols and atmospheric water and ice scattering light.

Credit: Earth Science Picture of the Day/Kosmas Gazeas

— Adam Voiland, NASA’s Earth Science News Team

Soaring for Science

NASA's Global Hawk autonomous plane

The newest bird in NASA’s flock — the unmanned Global Hawk — took off at 7 a.m. Pacific time today (April 2) from Dryden Flight Research Center at Edwards Air Force Base in California. The flight is the first airborne checkout of the plane since it was loaded with 11 science instruments for the Global Hawk Pacific (GloPac) mission.

Pilots are also streamlining processes to coordinate the workload while the nearly autonomous plane is flying at altitudes above 60,000 feet (almost twice as high as a commercial airliner). Operators and mission researchers are using the day to make sure all instruments are operating properly while in flight — particularly at the cold temperatures of high altitude — and communicating clearly with the plane and ground controllers. Mission participants expect to begin collecting data when actual GloPac science flights begin over the Pacific Ocean later this month.

GloPac is the Global Hawk’s first scientific mission. Instruments will sample the chemical composition of air in Earth’s two lowest atmospheric layers — the stratosphere and troposphere — and profile the dynamics and meteorology of both. They also will observe the distribution of clouds and aerosol particles. The instruments are operated by scientists and technicians from seven science institutions and are funded by NASA and the National Oceanic and Atmospheric Administration (NOAA).

Paul Newman, the co-mission scientist for GloPac, has been blogging about the mission on Earth Observatory’s “Notes from the Field” site. Here are a few excerpts to whet your appetite…

…There is an old Latin quote: “Maxima omnium virtutum est patientia.” Or “patience is the greatest virtue.” When it comes to mounting science instruments on an aircraft, you need to continually return to that quote…

…During the integration this week, we’ve had to cut holes into the aircraft. I told Chris Naftel, the Global Hawk project manager, that we had to cut some holes into the plane for the Meteorological Measurement System. Chris replied: “I don’t want to hear anything about the holes. It pains me!” In spite of Chris’ pain, the little holes are critical for measuring winds. You’re now asking, what? Little holes? For winds? It’s actually a very slick little measurement that relies on the work of Daniel Bernoulli, a Dutch mathematician who lived in the 1700s…

Can Something Out in Space be Good for Your Health on Earth?

An animation from Morain’s Center, viewable online by local residents, captured a storm crossing southeast Arizona and southwest New Mexico on Jan. 6-8, 2008. This clip, part of a 48-hour dust forecast, centers on the hour of peak dust concentration in the towns of Wilcox and Silver City. Credit: Morain/Earth Data Analysis Center

Stanley Morain is not an asthmatic. But like a lot of other healthy people, his lungs are sensitive to dust in the air in his hometown of Albuquerque. Dust makes him cough. It makes his eyes tear. It makes him pretty miserable.

Morain believed that if he — a healthy individual — is affected by the dust storms common to the American southwest, then hundreds of thousands of asthmatics must be affected far more severely when millions of tiny particles nestle into their respiratory systems.

His career has led him to a spot as director of the Earth Data Analysis Center at the University of New Mexico, where he has encouraged his colleagues and students to follow their hearts in the projects they pursue. He’s set the example by spending 10 years using NASA satellite data to create daily dust forecasts to improve health alerts.

I caught up with Morain a few days before he left for the American Meteorological Society’s annual meeting, where he gave a talk Tuesday about his work. He’s especially excited about decisions by the United Nations and the Joint Board of Geospatial Information Societies to publish his latest dust modeling work this spring.

WhatOnEarth: How did you decide to focus your career on using satellite sensors to improve public health?

Morain: The thought first struck me years ago, before I got my doctorate in biogeography and before I was awarded my first NASA research grant in 1964. I’ve always been fascinated by the geographic aspects of health even when I worked on NASA projects as dissimilar as lunar landers in the 1960s. I found we could combine information technology and modeling to learn more about health problems like heart attacks, Valley Fever, and hantavirus pulmonary syndrome that frequently strikes and kills young, otherwise healthy people within 24 hours.

WhatOnEarth: The Centers for Disease Control estimate 16.4 million adults and 7 million children in the U.S. suffer from asthma. How do your dust alerts help them?

Morain: Well, we’re not yet operational on a large-scale basis. That would take a commercial firm stepping in to make our alerts available nationwide. But, in my own backyard, the alerts are helping asthmatics plan for the worst days. Dust is a real problem here. When people know dust is headed their way, they can adapt their plans to minimize time outdoors or increase the dosage of some asthma medications. We’re making the alerts available, by way of summaries of dust and air quality conditions, to everyone from school nurses to TV news broadcasters to epidemiologists who are concerned about how long-term dust exposure affects the overall population.

WhatOnEarth: How do NASA satellites play into the development of the alerts?

Morain: There are environmental triggers for diseases like asthma. Very fine pollutant particles called aerosols are key examples of such triggers. NASA satellites like Terra and Aqua have instruments that can “see” the path dust takes. When you merge dust modeling information from the satellites with the National Weather Service weather forecasting model, you get a product that tells you when a weather event will bring dust along with it. The product becomes the basis for our daily dust alerts.

Three generations of model improvements for a dust storm across New Mexico and Texas on 15-16 December, 2003 illustrate (left) model performance before and (middle) after satellite data were included; and (right) the same storm modeled by the higher resolution, weather forecasting model Morain’s team uses. Credit: Morain/Earth Data Analysis Center

— Gretchen Cook-Anderson, NASA’s Earth Science News Team