Q & A: Michael Lefksy on Measuring Trees From Space

Colorado State University researcher Michael Lefsky recently published the first global map of forest heights using data from an radar-like laser instrument — the Geoscience Laser Altimeter System (GLAS) — aboard NASA’s IceSat satellite. The work should help scientists build an inventory of how muchcarbon the world’s forests store and how fast that carbon cycles throughecosystems and back into the atmosphere. We spoke with Michael to learn more about the work behind his work…

What on Earth: How did you get into this line of work?

Lefsky: I went to the University of Virginia to study the modeling of forest structure. My graduate advisor was working with NASA, and one day he came back with a single waveform lidar graph, one of the first ever produced. That was it: I knew this was what I wanted to work on.

What on Earth: What do you mean by forest structure and why go to the trouble of studying it?

Lefsky: We were looking at things like the size and number of stems in forests. We were also looking at how forests change over time and across landscapes. It’s critical to understand forest structure if you want to understand how much carbon forests are storing. You need to know whether a forest is growing, in stasis, or has been disturbed. We used to study this kind of thing by basically counting stems. But when I looked at that waveform lidar data, I could see it was a record of exactly the same thing, but from a completely different perspective.

What on Earth: I’m guessing you could collect in seconds the same amount of data it takes weeks to get in the field?

Lefsky: Actually, less than a second.

What on Earth: But are there insights that you can get from the ground that you can’t get from space?

Lefsky: Sure, but you have to keep the scale in mind. In the field, we basically estimate forest height by measuring diameter of trunks at breast height. That’s sort of like trying to study a person’s size and metabolism by measuring the diameter of their ankles. Lidar gives you a whole bunch of new information about the vertical structure of forest canopy. This is something that’s hardly ever investigated from the ground, or could only be investigated with great difficulty.

What on Earth: What are the most satisfying and frustrating aspects of working with remote sensing data?

Lefsky: I love what I do. I am incredibly lucky. I don’t really see frustrations, just challenges. In this case, there are enormous challenges involved with working on a completely new kind of data and figuring out how to process such large amounts of information. The flip side is that coming to new levels of understanding about what’s going on in the world is incredibly satisfying.


What on Earth: If there was one thing you wish people knew about your science, what would it be?

Lefsky: I wish people knew what tremendous things NASA’s Earth Science Division does for our understanding and ability to plan for the future of the global environment. People think space shuttle. People think the Moon. I think that the Earth science part of NASA is woefully under-appreciated.

— Adam Voiland, NASA’sEarth Science News Team

The map (left) was created by NASA’s Earth Observatory, using data provided by Michael Lefsky (above).   

The First A in NASA Stands for Aeronautics

                                                                                                                                                                                        Credit: NASA
If you’ve explored NASA’s website, you may have noticed that What on Earth is just one of a network of NASA blogs. You can find many of them on this main index page, but there are also NASA bloggers scattered at numerous other pages.

Earth Observatory’s Notes from the Field focuses, for example, on scientific field campaigns. And NASA’s Climate Change website, which is run by the Jet Propulsion Laboratory (JPL), features a blog called My Big Fat Planet. At Goddard Space Flight Center (GSFC), Geeked on Goddard (aka gogblog), written by a former Astronomy blogger, is fast becoming a go-to-source for all things Goddard (and includes plenty of earth science news).  

Tony Freeman, an earth science manager at JPL and occasional contributor to My Big Fat Planet, wrote a post this week that caught our eye. Tony shines a spotlight on our fleet of research aircraft, based mostly at Dryden Flight Research Center, and gives a fabulous reminder that the first A in NASA stands for aeronautics. Here’s how he explains why we bother with aircraft:

Why bother with aircraft when we can fly spacecraft? Well, airborne missions enable us to do unique — and crucial — experiments in the fields of atmospheric chemistry and volcanology, for example, from altitudes that range from 100 feet (30 meters) to 60,000 feet (18 kilometers). They also help us to check and validate the performance of the instruments that fly onboard NASA satellites such as Aqua, Aura, and others in the so-called “A-train” of Earth-observing satellites. And airborne instruments are often cheaper to launch. Tethered and untethered balloons; manned aircraft ranging from small propeller craft (think Cessna) to large jet engines (think the DC-8 aircraft); unmanned airplanes such as the large surveillance craft known as the Global Hawk — NASA uses them all.

You can read the rest of Tony’s post here.

NASA Earth Buzz: Soot, the Big Melt, and More


What on Earth Was That?
Last week, we asked you to identify the image on the left, and we received all sorts of replies. (Nope, it’s not an ant eating salt, spitting acid, or laying eggs). The correct answer? A microscopic view of soot from a wildfire. Check the original post for more details.

The Big Melt
A massive chunk of glacial ice tumbled from the shores of Greenland on July 6-7. The calving front – where the ice sheet meets the ocean – retreated nearly 1.5 kilometers (a mile) in a day. The mass of ice lost was nearly 1/8 the size of Manhattan. (NASA.gov)

Get a GRIP on This
A group of NASA researchers based in Florida and southern California won’t be sipping lemonade by the beach this summer. Instead, they’ll be chasing hurricanes with three NASA aircraft. (JPL News)

Record Setting Heat Sears Mid-Atlantic Region
After the whopper snowstorms this winter, a broiling heat wave has descended on the U.S. Mid-Atlantic. By June 28, Washington DC had endured 10 consecutive days where temperatures soared above 90°F (32° C). (Goddard DISC)

Climate Connections
Have questions about global warming and climate change? Tired of all the spin? Try these straightforward questions and answers from NASA scientists and science writers. (Earth Observatory)

Coming to a Theater Near You
You’d have to be living under a rock not to know that NASA studies the Moon, Mars, and deep space. But as a rocket-pack clad astronaut points out in a new video short at your local movie theater, a big part of our mission is to study Earth. (NASA Explorer)

A Porthole on the Arctic
Get a glimpse of science in action as NASA-funded researchers cruise the Arctic on an icebreaker. (NASA HQ Flickr)

Tweet of the Week
Floods kill an average of 140 people per year in the U.S., making it the number one severe weather killer. (SciJinks)

Aerosol image (left) from Peter Buseck, Arizona State University. Fire image (right) from Jim Ross, NASA Dryden Flight Research Center.

NASA's Count Rises as More Land Slides: An Interview with Dalia Kirschbaum


When a deadly landslide killed nearly 100 people and forced the evacuation of 75,000 in
Guatemala on May 30, NASA carefully documented it. And when more than 300 other rain-triggered landslides pulled the Earth out from beneath towns and villages in China, Uganda, Bangladesh, Pakistan and other countries in 2010, NASA researched and documented each one.

Sudden, rain-induced landslides kill thousands each year, yet no one organization had consistently catalogued them to evaluate historical trends, according to landslide expert Dalia Kirschbaum of NASA’s Goddard Space Flight Center. Three years ago, Kirschbaum set out to change that by creating a searchable inventory of landslides specifically triggered by rain.

WhatOnEarth spoke with Kirschbaum to understand how this tool might tell us more about when and where landslides are most likely to occur.

WhatOnEarth: What is a landslide?

Kirschbaum: Landslides occur when an environmental trigger like an extreme rain event — often a severe storm or hurricane – and gravity’s downward pull sets soil and rock in motion. Conditions beneath the surface are often unstable already, so the heavy rains or other trigger act as the last straw that causes mud, rocks, or debris — or all combined — to move rapidly down mountains and hillsides. Unfortunately, people and property are often swept up in these unexpected mass movements.

Landslides can also be caused by earthquakes, surface freezing and thawing, ice melt, the collapse of groundwater reservoirs, volcanic eruptions, and erosion at the base of a slope from the flow of river or ocean water. But torrential rains most commonly activate landslides. Our NASA inventory only tracks landslides brought on by rain.

WhatOnEarth: What prompted you to develop the NASA landslide inventory?

Kirschbaum: The project was initially meant to evaluate a procedure for forecasting landslide hazards globally. Studying landslide hazards over large areas is a thorny, complicated task because data collection is not always accurate and complete from one country to another. Improving our record-keeping is a first step in determining how to move forward with landslide hazard and risk assessments.

As a byproduct, we knew the catalog would provide information on the timing, location, and impacts of the landslides, which is valuable for exploring the socio-economic effects of these disasters. The International Disaster Database, the largest of its kind, often does not record smaller landslide events or detail their human or property toll.

Each one of our landslide entries contains information on the date of the event; details about the location; the latitude and longitude; an indication of the size of the event; the trigger; economic or social damages; and the number of fatalities.

WhatOnEarth: How is a landslide inventory useful or important?

Kirschbaum: As the catalog of events grows, we’ll be able to extract more and more information about which countries have the highest number of landslide reports, highest number of fatalities, etc. We can also break down events by region, season, and latitude, which helps us identify some large-scale patterns. Though the database is limited by occasional reporting biases and incomplete data, the catalog indicates that the highest reported number of rainfall-triggered landslides and fatal landslides occur in South and Southeastern Asia.

We also believe that in the longer term, the catalog will enable us to identify patterns in the global and regional frequency of landslides with respect to El Nino and related climate effects.

WhatOnEarth: Have you used satellite observations for the inventory?

Kirschbaum: No. In a few instances we’ve been able to obtain satellite images over an area where a landslide is clearly visible. However, landslides typically occur over small areas. Satellites cannot generally “see” such fine ground details or do not pass over the affected area with the frequency necessary to capture when the landslide occurred.

We hope to use satellite imagery, for example from NASA’s Earth Observing 1 (EO-1) satellite, to evaluate the location and area of some larger landslides. This remains a work in progress.

WhatOnEarth: So, if satellites can’t yet help you track landslides, how do you analyze each landslide event?

Kirschbaum: We have searched online literature – sources such as news reports, online journals and newspapers, and disaster databases — for the years 2003 and from 2007 to the present. The landslide inventory is only as good as the availability and accuracy of the reports and sources used to develop it. The work can be tedious and time-consuming, so we’ve enlisted the help of several excellent graduate students to keep the inventory updated over the past three years.

Our database tries to capture as many rainfall-triggered landslides as possible, but this is often difficult due to limitations in reporting of landslide hazards. The accuracy and completeness of details surrounding an event — especially when many landslides are triggered from a very large rainfall event over a broad area– can be less than informative so we are continually trying to improve the cataloguing effort. At the end of this year we’ll have a five-year record of events which will provide us more information to identify global trends.

WhatOnEarth: Is the NASA’s landslide inventory only available to lay people?

Kirschbaum: Our compilation methods were published in a scientific journal last year, and the actual inventory is now openly available to anyone on the Web. We’ll be posting the inventory from January through June 2010 shortly.

Image Information: A massive landslide covered the Philippine village of Guinsaugon, in 2007, killing roughly half of the 2,500 residents. Credit: U.S. Marine Corps./ Lance Cpl. Raymond Petersen III (top).  A map of landslide events in 2003, 2007, and 2008. Credit: NASA/Dalia Kirschbaum (above right).

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

What to Expect from the Arctic

Guest science writer KarenRomano Young reports from the ICESCAPEmission:

The U.S. Coast Guard Cutter Healy, our chunky red-and-white icebreaker, sits at the gates of the Arctic Ocean. In the wee hours this morning, the sun set and quickly rose again, and a rainbow stretched up into low clouds. The ICESCAPE mission had reached station 5 of a seven-stop transect of the Bering Strait, between Fairway Rock — resembling Kong Island, but with pointy ears — and Little Diomede (U.S.) — something like the “Cliffs of Insanity” in The Princess Bride. Close by is Big Diomede (Russia), topped with fog.

Movie references aside, this is a dramatic spot in which to find yourself when you wake up in the morning — or in the evening, as is the case for the half of the science crew working the night shift to process the samples.

It seems that no matter how many times a scientist has been to sea, it doesn’t get old. Greg Mitchell (below right), a specialist in ocean optics from the Scripps Institution of Oceanography, reckons he has spent about four years of his life aboard ships. His first trip to the Arctic was in 1987, his first year at Scripps. Mitchell’s research has taken him all over the world — to Antarctica and back again many times — but he hasn’t been inside the Arctic Circle since 1989. He expects change. Greg Mitchell

Observing the system…..and how it interacts with the edge of the sea ice…..and what’s going on with the ice melt…..and how it affects the ocean…..those principles won’t be any different than they were 20 years ago. “What we’re clearly seeing is that the sea ice is reducing more and more all the time,” said Mitchell. “This means less sunshine reflecting off the ice back into space, and more getting into the ocean.”

He expects the increase in sun-light on the sea to do three things:

  • “The light that’s not reflected will heat the ocean, accelerating the warming and accelerating the melting of the sea ice.”
  • “As the ocean warms it becomes more stratified. If you dive in a lake in the summertime, it’s warmer at the surface. But as you dive down, you feel the cold. That’s because the warm water is lighter than the cold water, and it stays at the surface. That’s thermal stratification. As you warm the ocean, it’ll stratify more and that will create a warm layer with a lot of light for algae to bloom (as long as they have nutrients).”
  • “More light in the ocean should cause more total photosynthesis in the Arctic, so we’ll lose habitat for polar bears but we’ll gain habitat for plankton.”

Like the rest of us, Mitchell is concerned about that. “I’m not saying it’s a good trade off. I think we should leave things alone. But the system’s changing, and as it changes we don’t know what the consequences of those changes will be. It’s hard to say what we could do. What we really need to do is to find a way for humans to have smaller footprint on earth. So we need to understand the processes better and then we need to model it.”

That’s why he’s here.

Mitchell, along with his group from Scripps, is involved in ground-truthing the optical properties of the Arctic Ocean (photos at the top and bottom of this post). That is, he’s helping to ensure that what they see at the surface squares up with the methods NASA satellites use to assess ocean color, an indicator of the level of chlorophyll and, by proxy, phytoplankton. NASA’s satellites measure the color of the ocean by flying over the earth and picking up blue, blue green, and green. If there’s not a lot of algae, the ocean is blue. If there is a lot of algae, the ocean is green.

But color is just one way of looking at phytoplankton levels. In order to truly assess the situation — for example how much carbon dioxide the phytoplankton are taking in – scientists need to assess the processes at work in the sea. “The optics don’t tell us this, so we have to take water samples, process the water, and then relate that to the optics we measure from the ship,” Mitchell said.

The global mapping you can see on the NASA site uses mathematical equations developed from the shipboard work. Satellite validation and calibration is based on the findings of scientists who go to sea and study the water to see what’s living there. Mitchell’s research group claims responsibility for about 20 percent of the global observations used by NASA for their models to convert satellite-measured optical measurements to chlorophyll estimates.

lowering gear from the Healy

The data contributes to models that allow prediction of primary production — the growth and health of organisms — under various conditions. Mitchell’s instruments include a small optical profiler — a fish-shaped instrument lowered from the Healy’s bow — and an optical package of instruments that measure water properties when it is lowered from the powerful A-frame at the stern.

“As ecologists, we don’t want to just know what color the ocean is,” he said. “We want to know how much plankton there is.” He walks to the edge of the ship and looks over the rail. “Now what we’re seeing out here is green water. There’s a lot of chlorophyll.” That means a strong pulse of phytoplankton, busy photosynthesizing the extra sunlight.

All photos shot by and courtesy of Karen Romano Young

NASA Earth Buzz: World Cup, New Climate Satellite, and a Five-Word Acceptance Speech We Love

Please view the slideshow on Firefox if you experience difficulty with Internet Explorer. You can also view it here and here.

World Cup Fever
You can’t quite make out the ball from space, but look at all that you can see (including a stadium and massive piles of slag in Johannesburg) in this soccer-inspired satellite slideshow. (NASA Goddard Flickr)

Adios El Niño, Hello La Niña?
The tropical Pacific has cooled during the last few months, perhaps foreshadowing a transition from El Niño to La Niña conditions. (Earth Observatory)

Just Five Words
NASA’s JPL-based climate change website picked up a Webby Award for best science site this week. We’re big fans of the 5-word-acceptance speech given by one of the site’s editors. (My Big Fat Planet)

Summer Haze
Clear skies, light winds, and long days with a high solar zenith are a recipe for haze and ozone–and that’s exactly what the last few days have brought in many parts of the country. (Smog Blog)

A Glorious New Mission
Enjoy the unique music–and an introduction to NASA’s newest climate monitoring satellite–in this newly released video about Glory. (NASA Explorer)

Tweet of the Week
From NASAHurricane: E.PACIFIC – Once a tropical storm, now a remnant, Blas has the blahs. Tropically speaking, that means that Blas is dissipating…. http://fb.me/BuNkFMJa (NASA Hurricane Page)

–Adam Voiland, NASA’s Earth Science News Team

Puzzling Over the Pieces

Guest contributor Karen Romano Young (photo at right) blogs from NASA’s ICESCAPE expedition…

There’s a sign on the door of the room I share with Sharmila Pal and Emily Peacock. It’s a green square of plastic engraved with a picture of a polar bear and the words “SCIENCE – LATE SLEEPER.” So many of the scientists aboard Coast Guard Cutter Healy for the ICESCAPE mission are awake through the night that the ship’s engraver, Chief Warrant Officer 3 Sean Lyons, has turned out a special  edition of late sleeper signs, complete with a rocket ship for NASA. Almost every door boasts a sleeper sign of one kind or another.

The reason? Aboard ICESCAPE, the science goes on 24 hours a day. We’re on a path to the far north, steaming from station to station through the night. Sometimes we’re in ice, sometimes we’re in open ocean, sometimes there’s a mix. Sometimes, there are walruses and seals. Each group of scientists has divided their schedule into shifts, so while some are catching their zzz’s behind those “late sleeper” signs, others are awake and overseeing operations, making measurements, and processing samples.

NASA’s Stanford Hooker takes the small boat out to measure light and take water samples, away from the interference of the ship. Karen Frey’s group from Clark University works on ice stations and takes Van Veen grabs in the open sea. (It’s like a giant pooper-scooper that scoops sediment from the ocean floor).

Bob Pickart of the Woods Hole Oceanographic Institution works to assess currents and other elements of physical oceanography, such as eddies and upwelling, as we pass through the ocean. James Swift, from Scripps Institution of Oceanography, oversees the CTD, a rosette of siphons and bottles triggered to sample water at various depths. (CTD stands for conductivity, temperature, and depth.) Greg Mitchell, Rick Reynolds, and their groups from Scripps measure the ocean’s optical properties with a small profiler dropped from the bow and with the Inherent Optical Properties (IOP) package of instruments deployed from the stern.


Sketch by Karen Romano Young

“We’re all working on different pieces of the same puzzle,” Reynolds says. “It’s impossible for one group to measure all we need to know. [Chief Scientist] Kevin Arrigo’s group is looking at core pigments, the plant pigments in the water column. Others are looking at chemical analyses of the nutrients in the water. It’s a big team effort. The ice people are working in a completely different environment, but there are algae in both places.”

The $250,000 IOP suite of instruments assesses the health of the ocean by analyzing the absorption and scattering of light by particles suspended in the water, including chlorophyll-rich algae; the quantity and quality of algae (the health and growth rate); and the presence of minerals and sediment. Each instrument on the IOP contributes to a picture of the makeup of the particles by assessing changes in light transmission.

“We start at the top,” says Reynolds (shown at left). “We look at what the NASAsatellite sees — the sea color — and parse out the differentcharacteristics of the water — how much algae, and what else is there,such as minerals from rivers, re-suspended sediment (mud stirred intothe water) and melting ice.” The resulting data will help thescientists develop new algorithms — equations for solving problems –to support the satellites.

NASA ice- and ocean-observing satellites, now working for more than ten years, are beginning to allow us to examine changes in the climate. One purpose of ICESCAPE is to look at the ocean with greater detail than the satellites offer, in order to improve and refine the interpretation of the satellite data. 

“We’re here because NASA wants to know what the satellites are seeing right here at the stations,” says Reynolds, “where nobody else may sample for decades, because the ocean is so vast.”

All imagery, including the IOP sketch, courtesy of Karen Romano Young 

Plankton on Parade

This is the last of four dispatches from guest writer Karen Romano Young. She spent time on the ICESCAPE expedition

The hypothesis has been proved conclusively aboard the Coast Guard Cutter Healy: I can officially sleep through anything. Yesterday [June 26] we hit what chief scientist Kevin Arrigo calls the heavy ice, northwest of Point Barrow, the northernmost point in the United States. Almost immediately we spotted a polar (right) bear, but haven’t seen one since. You can’t blame them for staying away from the Healy as it slams its 16,000 tons — plus the combined weight of everyone who spent the day eating the chocolate croissants Emily Peacock baked — into the ice.

Early this morning, the ice scientists stood on the bridge and targeted a floe for an “ice station.” For nine hours, we tried to get to it. Slowly and steadily, the ship made a path, ramming, cracking, or backing and ramming again, and the chopped-up ice in our wake soon froze together behind us. Scientist Sam Laney wishes he had a computer application that would detect seismic disturbances, saying he has lived through earthquakes registering 5.5 on the Richter scale and the vibrations didn’t feel as strong as they do right now.

[Laney commented later: “I actually downloaded a program last night and took a few hours of measurements in the aft hose reel room. I am not a seismologist, of course, but I’m estimating between 4.3 and 4.9 on the Richter scale based on these crude measurements.” This is why I like to hang out with scientists. ]

You can see the ice on a map compiled from satellite data, but the reality of the sea ice is right here at sea level. It’s quite different thing to see it in a satellite image as opposed to falling over in the shower because your ship is tilting as it climbs a ridge of jammed-together ice floes and slides back down.

The sea ice measurements made by a dozen scientists on the ice for our station will help confirm details in the satellite maps, just as the work of those studying optics in the open sea will add to the sea color (chlorophyll) mapping that NASA does.

But there is an additional method of observing the Arctic Ocean that I’d like to tell you about because it has been so exciting to everyone here at ICESCAPE. You don’t have to interpret maps or charts of data. You just have to sit back, put your feet up, and check out Sam Laney’s pictures.

Sam’s images come from a stream of water coming up through a hose at Healy’s stern. All the microscopic organisms in the stream parade in front of a camera, sitting briefly for a snapshot before returning to the sea. The instrument, which is set up deep below in the aft hose reel room, is called the Imaging FlowCytobot (below right). It was developed at the Woods Hole Oceanographic Institution.

Flow cytometry has long been used in medicine for counting cells — such as platelets – in blood samples as they are squirted past a laser. Oceanographers use flow cytometers to count the small cells that live in seawater, such as phytoplankton (photosynthetic microbes) and other small organisms. 

Imaging flow cytometry takes this approach one step further by triggering a camera every time a cell passes in front of the laser beam. Software on the imager immediately crops out the background from the picture to focus on the critter that was just photo-graphed. The revolutionary result is a steady flow of pictures of organisms as small as 2 microns living in seawater. It looks like a case of jewels: individual round-bodied gems, bigger broach-like diatoms chains (above right), and monster-like ciliates that prey on the smaller critters. 

In the past, scientists were able to gather steady flows of water and videotape the plankton at magnification. But managing this huge amount of data would have taken such incredible man-hours that it was impractical for use at sea. The Imaging FlowCytobot does it for us, snapping off a continuous stream of pictures — as many as ten thou-sand cells in a volume of seawater no bigger than a AA battery

Laney’s sea-going imager is an outgrowth of an underwater Imaging FlowCytobot that his collaborators Heidi Sosik and Rob Olson have operated for several years at the Martha’ Vineyard Coastal Observatory off Massachusetts. ICESCAPE is the first time the instrument has been used at sea to survey broad regions of the ocean.

“We are seeing what’s in the water immediately, not after the fact in a lab,” Laney explained, “so it’s obvious when the water — and what’s in it — changes. In the images taken north of Dutch Harbor, there weren’t many cells out there because it’s the open ocean. But in the Bering Strait, the jewels were much more elaborate because we were closer to shore. A large diatom chain indicates an ecosystem that has a lot of nutrients and is highly productive.”

Laney, Sosik, and Olson hope to see Imaging FlowCytobots placed aboard long-term, deep-ocean moorings in the open sea, such as those that will be deployed as part of the Ocean Observing System.

Of course, some of the fun is just seeing the plankton in action. Sometimes you can simply tell that they’re ailing or dying. In one memorable stretch of sea, off Point Lay, the Cytobot caught a stream of diatoms in the act of dividing and reproducing. Then there are the horror shots, in which a ciliate stretches its cilia toward a hapless phytoplankton.

Imagery courtesy of Karen Romano Young. The polar bear was photographed by Gert van Dijken. 

A Tale of Two Kenyas: Contradictions in Air Quality Stirred Researcher’s Pursuit of Atmospheric Science

Charles Kironji Gatebe’s early years read like a cliché. He grew up barefoot and poor in the small Kenyan village of Kenda at the foot of Mount Kenya, the son of coffee sharecroppers who raised their family on pennies a day. He walked nearly 10 miles each way to school for nearly a decade. He lacked adequate texts and other school supplies.

What he didn’t lack on those long daily walks was clean air. It was the contrast between the clear skies of his boyhood home and the smog and fumes of the nation’s capital, Nairobi, that stirred within Gatebe a strong passion for science. In 1979, Gatebe (right) was selected to represent his elementary school at a national convention to celebrate the United Nations Educational, Scientific and Cultural Organization’s (UNESCO) International Year of the Child. He later won a physics prize in high school in 1984 from the Kenya Secondary Schools Science Congress. He enjoyed independent research so much that his physics teacher would allow him to conduct his own experiments in the lab alone at night or on weekends.

Gatebe’s passion, matched with natural aptitude, eventually led Gatebe to degrees from Kenya’s University of Nairobi and the University of the Witwatersrand in South Africa. Now a climatologist with a joint appointment at NASA’s Goddard Space Flight Center and the University of Maryland-Baltimore County, Gatebe has fashioned an award-winning career – including the rare honor of the World Meteorological Organization’s Young Scientist Award in 2000, and awards from the Kenyan government, German Academic Exchange Services, SysTem for Analysis, Research and Training (START), and the International Program in the Physical Sciences — for his innovative research on air pollution and its sources and effects on his country.

“Air quality in Kenya’s villages was and continues to be significantly different from the smog encountered in Nairobi. They vary so much that it seems you’re virtually in two distinct countries,” said Gatebe when asked to share what sparked his study of Kenya’s air pollution. During his graduate studies at the University of Nairobi, he devised a few climate projects that unexpectedly got the attention of the Kenyan government and United Nations Environment Program. One of those was a modeling experiment to measure vehicle pollution and predict pollution levels from the average speed and number of cars in use.

Gatebe also investigated the origins of the city’s air pollution; that is, how much Nairobi’s citizens and industry generated compared to what was transported in from other countries. “Charles’ Kenyan air quality research was quite breathtaking and significant,” said Michael King, a senior atmospheric scientist at the University of Colorado and former senior project scientist at NASA Goddard who recruited Gatebe to NASA in 1999. “It involved him regularly hiking to the top of Mount Kenya – which sits roughly on the equator — and collecting air samples of atmospheric aerosol particles that he analyzed for their composition to distinguish dust and other particles from local sources from pollutants arriving from as far away as southern Africa, India and the Sahara.”

The acclaim from the study came as a surprise, Gatebe says, but motivated him to stay the course. He knew he’d found his niche.

As a former child scientist, Gatebe is eager to inspire more kids to get involved in science. He’s dedicated himself to NASA’s Global Learning and Observations to Benefit the Environment (GLOBE) education program, and blogs about the science of current events for GLOBE’s Web site.

Gatebe’s latest work is based on what he calls an accidental discovery, not uncommon in science. In summer of 2008, he was part of a NASA field mission called Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS). Arctic wind currents can carry a haze that affects local climate. Gatebe and colleagues flew aboard planes through smoke blown over the Pacific Ocean from land-based fires to evaluate the composition of the pollution that eventually forms Arctic haze. 

A ship passed beneath Gatebe’s plane, through his measurement field, triggering a mass of sea foam in its wake. When he later evaluated visible and near-infrared data from NASA’s Cloud Absorption Radiometer instrument that took the measurements from aboard the plane, he noticed a spike in brightness in the vicinity of the ship’s path. The bubbles in the wake increased light reflectance off the ocean.

The irony of the discovery was quite amazing to Gatebe. Ships were long thought to pollute the air and contribute to warmer climate through exhaust emissions. But they also appear to have a counterbalancing effect of cooling local ocean surfaces by as much as four percent. What he doesn’t know yet is just how much the cooling effect offsets the warming effect on the nearby environment. He hopes that others will further the work so the question doesn’t go unanswered.  

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


Charles K. Gatebe (top, courtesy of C. Gatebe);  Zebras with hazy Nairobi in the distance (bottom, courtesy of Michael King).  

NASA Earth Buzz

Earth science links, video, and more that caught our eye…


Tragedy in the Gulf
Heartbreaking video (above) from NASA shows a time-series of satellite snapshots of oil tendrils as they spread through the Gulf of Mexico. The video has appeared on the New Yorker and Gizmodo web sites and has garnered more than 600,000 views on YouTube. (NASAExplorer)

Who CARES About Urban Aerosols?
NASA scientist Matteo Ottiviani is blogging from an airborne field campaign in California, and he has a gift for making aerosols (small particles in the air, not the spray cans) sound exciting.   (Notes from the Field)

NASA Expedition Heads to the Arctic
Yep, we work from ships, too. A NASA-funded expedition has set sail for the Beaufort and Chukchi seas above Alaska to study the ecological impacts of sea ice decline. (IceScape Blog)

Supercomputing Climate Simulation Center Debuts
Many skeptics point to erratic models as the Achilles heel of climatology. A recently unveiled supercomputing center at Goddard, packed with more than 10,000 computer processors, should help. (NASA.gov)

Sensing the Sun’s Irradiance
Little fluctuations in the sun’s output might have more impact than you might think. A Q & A with the Glory Mission’s Judith Lean explores what it all means for climate. (NASA Earth Observatory)

New Earth Observer Is out
NASA’s bimonthly newsletter Earth Observer has news about IceSat, IceBridge, sea ice and more. It’s a somewhat technical read, but worth checking out. (Earth Observer – PDF)

Tweet of the Week
Why is permafrost like frozen chicken? http://go.usa.gov/3Ka (@NASA)

Though you may not know it, NASA has tens of thousands of websites devoted to earth science. It would be a Herculean task to keep track of all of them, so we created this column to save you the trouble. We’ll periodically scour what NASA has to offer and serve up the most fascinating, surprising, and thought-provoking Earth science we stumble across. Think we missed something? Post a comment in the most recent Earth Buzz.

–Adam Voiland, NASA’s Earth Science News Team