NCDC Releases 2014 U.S. Climate Report

The 2014 annual average contiguous U.S. temperature was 52.6°F, 0.5°F above the 20th century average. This ranked as the 34th warmest year in the 1895–2014 record. Very warm conditions dominated the West, while the Midwest and Mississippi Valley were cool.

The average contiguous U.S. precipitation was 30.76 inches, 0.82 inch above average, and ranked as the 40th wettest year in the 120-year period of record. The northern United States was wet, and the Southern Plains were dry; the national drought footprint shrank about 2 percent. 

In 2014, there were eight weather and climate disaster events with losses exceeding $1 billion each across the United States. These eight events resulted in the deaths of 53 people. The events include: the western U.S. drought, the Michigan and Northeast flooding event, five severe storm events, and one winter storm event. 

This summary from NOAA's National Climatic Data Center is part of the suite of climate services NOAA provides to government, business, academia, and the public to support informed decision making.

Source: NOAA

Solar photons drive water off the moon

Lunar sample in vacuum. A lunar sample in a ultra-high vacuum system is hit with ultraviolet (157 nm) photons to simulate conditions in space. Credit: Image courtesy of Georgia Institute of Technology

Water is thought to be embedded in the moon's rocks or, if cold enough, "stuck" on their surfaces. It's predominantly found at the poles. But scientists probably won't find it intact on the sunlit side.

New research at the Georgia Institute of Technology indicates that ultraviolet photons emitted by the sun likely cause H2O molecules to either quickly desorb or break apart. The fragments of water may remain on the lunar surface, but the presence of useful amounts of water on the sunward side is not likely.

The Georgia Tech team built an ultra-high vacuum system that simulates conditions in space, then performed the first-ever reported measurement of the water photodesorption cross section from an actual lunar sample. The machine zapped a small piece of the moon with ultraviolet (157 nm) photons to create excited states and watched what happened to the water molecules. They either came off with a cross section of ~ 6 x 10−19 cm2 or broke apart with a cross section of ~ 5 x 10−19 cm2.. According to the team's measurements, approximately one in every 1,000 molecules leave the lunar surface simply due to absorption of UV light.

Georgia Tech's cross section values can now be used by scientists attempting to find water throughout the solar system and beyond.

"The cross section is an important number planetary scientists, astrochemists and the astrophysics community need for models regarding the fate of water on comets, moons, asteroids, other airless bodies and interstellar grains," said Thomas Orlando, the Georgia Tech professor who led the study.

The number is relatively large, which establishes that solar UV photons are likely removing water from the moon's surface. This research, which was carried out primarily by former Georgia Tech Ph.D. student Alice DeSimone, indicates the cross sections increase even more with decreasing water coverage. That's why it's not likely that water remains intact as H2O on the sunny side of the moon. Orlando compares it to sitting outside on a summer day.

"If a lot of sunlight is hitting me, the probability of me getting sunburned is pretty high," said Orlando, a professor in the School of Chemistry and Biochemistry and School of Physics. "It's similar on the moon. There's a fixed solar flux of energetic photons that hit the sunlit surface, and there's a pretty good probability they remove water or damage the molecules."

The result, according to Orlando, is the release of molecules such as H2O, H2 and OH as well as the atomic fragments H and O. The research is published in two companion articles in the Journal of Geophysical Research: Planets. The first discusses the water photodesorption. The second paper details the photodissociation of water and the O(3PJ) formation on a lunar impact melt breccia.

Orlando is the associate director of Georgia Tech's Center for Space Technology and Research (C-STAR). C-STAR is an interdisciplinary research center that serves to organize, integrate and facilitate the impact of Georgia Tech's space science and space technology research activities. The center brings together a wide range of Georgia Tech faculty, active in space science and space technology research, and functions as the Institute's focal point for growth of the space industry in the state of Georgia.

Source: Georgia Institute of Technology

Move over smart cities, the Internet of Things is off to the country

Smart sheep

 Lancaster University is about to take the concept of smart cities out of town. Computer scientists at Lancaster University are investigating how the Internet of Things could work in the countryside.

The Internet of Things - which enables object-to-object communication over the internet and real time data monitoring - has typically been associated with urban environments and until now the countryside has been left out in the cold.

Computer scientist Professor Gordon Blair of Lancaster University has won £171,495 from the Engineering and Physical Sciences Research Council to lead a new project in Conwy, North Wales, which will investigate how the Internet of Things could work in the countryside.

Working with partners at the Centre for Ecology and Hydrology, The British Geological Survey and Bangor University, the project launched on December 1 and will run for 18 months.

Problems from flooding and agricultural pollution to animal movements and drought could all potentially benefit from smart technology in the sticks.

The Internet of Things, which takes everyday objects and hooks them up to the internet, represents a shift in the way we gather and engage with information. Applying this booming technology to the countryside presents challenges – for example how to build a network when there are mountains and trees in the way – but researchers believe the benefits could be huge.

Sheep with digital collars, sensors on riverbanks, rainfall and river flow monitors could all soon form part of the project.

Professor Blair said: “Cities have been the focus of much of the boom in this type of technology – it has been used to keep traffic flowing on our roads, monitor air pollution and even help us find a parking spot on a busy Saturday afternoon. But the countryside faces challenges of its own, from subtle environmental changes to catastrophic events such as flooding. The possibilities of bringing the Internet of Things to the countryside are limitless. The next step will be to identify exactly what will be of most use in the short term and how we will frame the project.”

Source: Lancaster University

Tree diseases can help forests

A healthy seedling of the tree Castilla elastica is on the left, while a dying seedling, attacked by a plant pathogen, is on the right. A study in the Journal of Ecology by University of Utah biologists shows that such tree diseases, while killing individual seedlings, can increase forest biodiversity. Credit: Erin Spear, University of Utah.

Plant diseases attack trees and crops and can hurt lumber and food production, but University of Utah biologists found that pathogens that kill tree seedlings actually can make forests more diverse.

While low rainfall has been blamed for a lack of drought-sensitive trees near the Pacific side of the Panama Canal, the new study answers a mystery about what keeps drought-tolerant trees from that area from living along the wetter Caribbean side of the canal. The answer: disease-causing plant pathogens, the researchers report in their study, published online Wednesday, Nov. 12 by the Journal of Ecology.

"Because seedlings of disease-sensitive tree species can't survive in the wetter forests and drought-sensitive tree species cannot survive in the drier forests, different tree species inhabit the wetter and drier forests even though they are only 30 miles apart" in Panama, says Phyllis Coley, a senior author of the study and a distinguished professor of biology.
In other words, tree pathogens contribute to the staggering diversity of trees in Panama's tropical forests, she adds.

The study's first author, biology doctoral student Erin Spear, says that is important because "conservation planning and predictions about how tree species distributions may shift with climate change require an understanding of the factors currently influencing where species can and cannot survive."

That is particularly important in tropical forests and other forests that are under elevated threat of deforestation.

Funding for the study came from Sigma Xi -- The Scientific Research Society, the Smithsonian Institution and the National Science Foundation.

Of Forests and Pathogens

Tropical forests are threatened, and dry tropical forests are even more threatened because sunnier, drier climates are better for growing crops and are favored by people. Some 90 percent of Panama's residents live on the nation's drier Pacific slope.

Forests are essential for feeding and sheltering animals, providing important medicines, storing carbon and water, and reducing erosion by holding soil in place. These functions are influenced by different species inhabiting a forest, so it is essential to understand why certain tree species can survive in certain areas but not others.

Panama's forests also are important economically because tree roots limit how much soil erodes into the Panama Canal, ensuring that huge container ships can pass. Researchers also believe the forests help maintain water levels in the canal because forest soil stores water, slowly releasing it into streams feeding the canal during the dry season.

Diversity is high in tropical forests. A 930-square-mile area bordering the Panama Canal has more than 800 tree species. By comparison, about half the state of Rhode Island -- or some 610 square miles -- is forested, and that area has only 51 tree species.

Part of the reason Panama's forests have more species is because the Pacific end of the canal receives less annual rainfall -- about 5.9 feet -- than the Caribbean end, where 9.8 feet of rain falls annually.

"While there is considerable evidence that less rain in the drier, Pacific forests means that drought-sensitive tree species can't survive there, it has been unclear what prevents the drought-tolerant species of the drier forests from living in the wetter forests," says University of Utah biology professor Tom Kursar, the study's other senior author. "Our study tackled that unanswered question."

So Spear braved mud, rain, insects and snakes to monitor seedlings of a variety of tree species in the wetter and drier forests of central Panama for pathogen-caused damage and death. Plant pathogens that make plants sick include bacteria, viruses and fungi.

Spear says the researchers' findings suggest that "all seedlings are at a greater risk of being injured and killed by pathogens in the wetter forests than in the drier forests." This could be because the damp environment of the wetter forests helps pathogens survive, and more rainfall helps pathogens move from one seedling to another.

But that's only half the story. Coley says that their study indicates "pathogens are implicated in the absence of the dry-forest tree species from the wetter forests, where they might otherwise be able to live. That is because dry-forest tree species are more likely to die from pathogen attack than wet-forest species."

Diagnosing Sick Seedlings

Spear collected the seeds for the study by hiking for miles, kayaking in the canal to collect fruit from overhanging branches, and even riding a crane-carried gondola more than 100 feet upward into the forest canopy.

She conducted the study at two forest sites in central Panama: one at the large Metropolitan Natural Park in Panama City on the drier Pacific side, and one on private property in the Santa Rita Ridge area on the wetter Caribbean side. She planted "gardens" of tree seeds -- including species typical of wetter and drier forests -- in 30 locations at each site. More than 1,000 seeds were planted; 725 of them sprouted.

Once the seeds were planted, the researchers covered them with wire mesh to protect the seeds and seedlings from being crushed by tree branches or eaten by animals.

Spear visited both sites weekly and took notes on the 725 seedlings. Weekly visits were essential because, diseased seedlings can be dead and decomposing within days.

"We monitored when the seeds germinated, the occurrence of and date when symptoms of pathogen attack were observed, if and when a seedling died, and we ascribed a cause of death," Spear says. Pathogen symptoms included patches of black, dead tissue in the leaves or stem. "In some cases, we could actually see the pathogen growing on the seedling," she says.

Of the 725 seedlings that germinated, 38 percent suffered pathogen-caused damage, including 11 percent of seedlings killed by pathogens.

Compared with seedlings in the drier forest, seedlings in the wetter forest were 74 percent more likely to suffer pathogen-caused damage and 65 percent more likely to be killed by pathogens.

"But what was really striking was that pathogen-caused damage was five times more likely to be lethal for seedlings of dry-forest species than for wet-forest species," suggesting dry- and wet-forest species differ in their ability to halt or slow infection, Spear says.

The researchers next plan to identify specific fungi, bacteria and other pathogens and whether they differ in wetter and drier forests.

During her study at the drier park site in Panama City, Spear discussed her research with tourists and other park visitors.

"I'd emerge from the tangles of vines sweaty, muddy and generally disheveled and people couldn't help but ask what I was doing," Spear recalls. "It was heartening to hear how the forest had touched these very different people."

A brief time-lapse video of a seedling dying from pathogen attack during a period of several days can be seen at: http://vimeo.com/58026978 Video by Erin Spear, University of Utah.


Source: University of Utah

If trees could talk: Forest research network reveals global change effects

In addition to identifying, mapping, measuring and monitoring trees in the CTFS-ForestGEO study plots, researchers describe the relatedness of trees, track flower and seed production, collect insects, survey mammals, quantify carbon stocks and flows within the ecosystem, take soil samples and measure climate variables like rainfall and temperature. The thorough study of these plots provides insights into not only how forests are changing but also why. Credit: Beth King, STRI

Permafrost thaw drives forest loss in Canada, while drought has killed trees in Panama, southern India and Borneo. In the U.S., in Virginia, over-abundant deer eat trees before they reach maturity, while nitrogen pollution has changed soil chemistry in Canada and Panama. Continents apart, these changes have all been documented by the Smithsonian-led Center for Tropical Forest Science-Forest Global Earth Observatory, CTFS-ForestGEO, which released a new report revealing how forests are changing worldwide.

"With 107 collaborators we've published a major overview of what 59 forests in 24 countries, where we monitor nearly 6 million trees teach us about forest responses to global change," said Kristina Anderson-Teixeira, first author of the report and CTFS-ForestGEO and ecosystem ecologist based at the Smithsonian Conservation Biology Institute.

Many of the changes occurring in forests worldwide are attributable to human impacts on climate, atmospheric chemistry, land use and animal populations that are so pervasive as to warrant classification of a new geologic period in Earth's history -- the Anthropocene, the Age of Humans.

Measuring and understanding the effects of all these changes -- collectively termed "global change" -- are easier said than done. Some of the best information about these global-scale changes comes from CTFS-ForestGEO, the only network of standardized forest-monitoring sites that span the globe.

Since the censuses began at the first site on Barro Colorado Island in Panama in 1981, atmospheric carbon dioxide has increased by 16 percent. The forest sites in the network have warmed by an average of over 1 degree F (0.6 degree C) and experienced up to 30 percent changes in precipitation. Landscapes around protected sites experience deforestation.
The plot network now includes forests from Brazil to northern Canada, from Gabon to England and from Papua New Guinea to China.

In addition to identifying, mapping, measuring and monitoring trees, researchers describe the relatedness of trees, track flower and seed production, collect insects, survey mammals, quantify carbon stocks and flows within the ecosystem, take soil samples and measure climate variables like rainfall and temperature. The thorough study of these plots provides insights into not only how forests are changing but also why.

Climate change scenarios predict that most of these sites will face warmer and often drier conditions in the future -- some experiencing novel climates with no modern analogs. Forests are changing more rapidly than expected by chance alone, and shifts in species composition have been associated with environmental change. Biomass increased at many tropical sites across the network.

"It is incredibly rewarding to work with a team of forest scientists from 78 research institutions around the world, including four Smithsonian units" Anderson-Teixeira said. "CTFS-ForestGEO is a pioneer in the kind of collaborative effort it takes to understand how forests worldwide are changing."

"We look forward to using the CTFS-ForestGEO network to continue to understand how and why forests respond to change, and what this means for the climate, biodiversity conservation and human well-being," said Stuart Davies, network director.

Source: Smithsonian Tropical Research Institute

Early warning signals of abrupt climate change

Drought (stock image). Credit: © carloscastilla / Fotolia

A new study by researchers at the University of Exeter has found early warning signals of a reorganisation of the Atlantic ocean's circulation which could have a profound impact on the global climate system.

The research, published today in the journal Nature Communications, used a simulation from a highly complex model to analyse the Atlantic Meridional Overturning Circulation (AMOC), an important component of the Earth's climate system.

It showed that early warning signals are present up to 250 years before it collapses, suggesting that scientists could monitor the real world overturning circulation for the same signals.

The AMOC is like a conveyor belt in the ocean, driven by the salinity and temperature of the water. The system transports heat energy from the tropics and Southern Hemisphere to the North Atlantic, where it is transferred to the atmosphere.

Experiments suggest that if the AMOC is 'switched off' by extra freshwater entering the North Atlantic, surface air temperature in the North Atlantic region would cool by around 1-3°C, with enhanced cooling of up to 8°C in the worst affected regions.

The collapse would also encourage drought in the Sahel -- the area just south of the Sahara desert -- and dynamic changes in sea level of up to 80cm along the coasts of Europe and North America.

"We found that natural fluctuations in the circulation were getting longer-lived as the collapse was approached, a phenomenon known as critical slowing down," said lead author Chris Boulton.

"We don't know how close we are to a collapse of the circulation, but a real world early warning could help us prevent it, or at least prepare for the consequences" adds co-author Professor Tim Lenton.

The study is the most realistic simulation of the climate system in which this type of early warning signal has been tested.

"The best early warning signals in the model world are in places where major efforts are going into monitoring the circulation in the real world -- so these efforts could have unexpected added value' adds Professor Lenton.

Source: University of Exeter

Groundwater patches play important role in forest health, water quality

This is Kevin McGuire, associate director of the Virginia Water Resources Research Center. Credit: Virginia Tech

Even during summer dry spells, some isolated patches of soil in forested watersheds remain waterlogged.

These patches act as hot spots of microbial activity that remove nitrogen from groundwater and return it to the atmosphere, researchers from several institutions, including Virginia Tech, report in a leading scientific journal.

The discovery provides insight into the health of a forest. Nitrogen is an important nutrient for plant growth and productivity, but in streams, it can be a pollutant.

"The importance of these fragmented patches of saturated soil and their role in the fate of nitrogen in forested watersheds has been underappreciated until recently," said Kevin McGuire, an associate director of the Virginia Water Resources Research Center based in Virginia Tech's College of Natural Resources and Environment, co-author of the article to be published in the Proceedings of the National Academy of Sciences.

"We were able to determine the importance of denitrification in patches of shallow groundwater, which have largely been overlooked control points for nitrogen loss from temperate forested watersheds," McGuire said.

Most nitrogen is deposited by rain. Temperate forests receive much larger inputs of nitrogen from the atmosphere than they export to streams. Once nitrogen leaves the forest in streams, it can become a water pollutant.

"In some ecosystems, there have been long-term declines in stream water export of nitrogen when inputs have remained elevated," said co-author Christine Goodale, an associate professor of ecology and evolutionary biology at Cornell University.

"Understanding the fate of this nitrogen has been a challenge because denitrification -- a gaseous loss of nitrogen to the atmosphere -- is notoriously difficult to measure," said co-author Peter Groffman, an expert on denitrification at the Cary Institute of Ecosystem Studies.

Denitrification removes nitrogen from water and can therefore improve water quality in downstream lakes and estuaries.

However, nitrogen is also an important nutrient for plant growth in the forest so removals of nitrogen by natural processes can reduce the productivity of the forest.
The research, led by Sarah Wexler while she was a postdoctoral associate in hydrology and stable isotope geochemistry at Cornell University, took place in the Hubbard Brook Experimental Forest in the White Mountains of New Hampshire, where the atmosphere annually deposits five to seven pounds of nitrogen per acre.

The Hubbard Brook Experimental Forest is part of the National Science Foundation's Long Term Ecological Research Network.

McGuire, also an associate professor of hydrology in the Department of Forest Resources and Environmental Conservation, led another National Science Foundation-funded project at the site, which developed an organizing framework to describe and map variations of soil in the watershed that explain shallow groundwater occurrence and frequency.
Groundwater wells from this earlier study were used in the new research to monitor soils that may have had the right conditions to function as hot spots for denitrification.

At sites throughout the forest, the research team measured the presence of nitrate, a form of nitrogen that is highly mobile and reactive in the environment, determined whether the nitrate is a result of atmospheric deposition or microbial conversion, and discovered the nitrogen loss to the atmosphere.

"We were able to differentiate sources of nitrate and show that some of the nitrate was lost to the atmosphere by looking at nitrate at the atomic level, that is, at the isotopic composition of the nitrogen and oxygen in nitrate," said Wexler, who is now at the School of Environmental Sciences at the University of East Anglia in the United Kingdom. "The isotopic composition of nitrate provides a natural way to directly track the details of nitrogen cycling."

McGurie said, "Some work remains to be done, but the aim is to be able to develop a better sense of where and how nitrogen is processed in the environment and be in a position to predict how changes in climate, for example warmer and wetter conditions, affect nitrogen cycling and water quality in forested ecosystems."

Source: Virginia Tech

NASA study shows 13-year record of drying Amazon caused vegetation declines

Change in Amazon greenness from 2000 to 2012, measured as Normalized Difference Vegetation Index (NDVI). Greener colors represent increased greenness, gray is no change, and yellow represents decreased greenness over the 13-year record.
Credit: Hilker et al.

13-year decline in vegetation in the eastern and southeastern Amazon has been linked to a decade-long rainfall decline in the region, a new NASA-funded study finds.

With global climate models projecting further drying over the Amazon in the future, the potential loss of vegetation and the associated loss of carbon storage may speed up global climate change.

The study was based on a new way to measure the "greenness" of plants and trees using satellites. While one NASA satellite measured up to 25 percent decline in rainfall across two thirds of the Amazon from 2000 to 2012, a set of different satellite instruments observed a 0.8 percent decline in greenness over the Amazon. The study was published on Nov. 11 in Proceedings of the National Academy of Sciences.

While the decline of green vegetation was small, the area affected was not: 2.1 million square miles (5.4 million square kilometers), equivalent to over half the area of the continental United States. The Amazon's tropical forests are one of the largest sinks for atmospheric carbon dioxide on the planet.

"In other words, if greenness declines, this is an indication that less carbon will be removed from the atmosphere. The carbon storage of the Amazon basin is huge, and losing the ability to take up as much carbon could have global implications for climate change," said lead author Thomas Hilker, remote sensing specialist at Oregon State University in Corvallis, Oregon.

Plants absorb carbon dioxide as part of photosynthesis, the process by which green plants harvest sunlight. The healthier the plants, the greener the forest.

The Amazon basin stores an estimated 120 billion tons of Earth's carbon -- that's about 3 times more carbon than humans release into the atmosphere each year. If vegetation becomes less green, it would absorb less of that carbon dioxide. As a result, more of human emissions would remain in the atmosphere, increasing the greenhouse effect that contributes to global warming and alters Earth's climate.

Can't See the Forest for the Clouds

Teasing out changes in vegetation greenness over the Amazon is one of the most challenging problems for satellite remote sensors because there's no tougher place on Earth to observe the surface.

"The wet season has typically 85 to over 95 percent cloudiness from late morning to early afternoon, when NASA satellites make measurements," said co-author and remote sensing specialist Alexei Lyapustin of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Even during the dry season the average cloudiness can be on the order of 50 to 70 percent." Add other atmospheric effects, soot and other particles released from fires during the dryer months, and it's very difficult for the satellite to pick up a clear signal of the surface, Lyapustin added.

Using the Moderate Resolution Imaging Spectroradiometer, or MODIS, instruments aboard NASA's Terra and Aqua satellites, Hilker, Lyapustin and their colleagues developed a new method to detect and remove clouds and other sources of error in the data. It looks at the same location on Earth's surface day after day over time and analysts pick out a pattern that is stable in contrast to the ever-changing clouds and aerosols. This knowledge of what the surface should look like from earlier observations is used later to detect and remove the atmospheric noise caused by clouds and aerosols. It's as if the signal from the ground were a song on a static-y radio station, and by listening to it over and over again for long enough, the new method detects and removes the static. By reducing those errors, they increased the accuracy of the greenness measurements over the Amazon.

"We're much more confident that this is a gap between clouds where we can measure greenness, but standard algorithms would call it a cloud," said Lyapustin. "We can get more data about the surface, and we can start seeing more subtle changes."

One of the subtle changes visible in the new data-set is how the Amazon's greenness corresponds to one of the long-known causes of rainfall or drought to the Amazon basin: changes in sea surface temperatures in the eastern Pacific Ocean, called the El Nino Southern Oscillation. During warmer and dryer El Nino years, the Amazon appears browner. During cooler La Nina wet years, the Amazon appears greener.

In the past, with greenness data, "it's been hard to tell an El Nino year from a non-El Nino year," said Lyapustin.

The effects of large and more frequent droughts may have lasting impacts that contribute to the long-term decline in vegetation, especially in an increasingly water stressed ecosystem. Many climate models project that in the future, El Nino and La Nina events will become more intense. They also project a northward shift of the main rain belt that provides 

moisture to the Amazon rainforest, which could further reduce rainfall to the region.

"Our observations are too short to link drying to human causes," Hilker said. "But if, as global circulation models suggest, drying continues, our results provide evidence that this could degrade the Amazonian forest canopies, which would have cascading effects on global carbon and climate dynamics."

Limits of Light vs. Water

The researchers found another subtlety in the Amazon's response to rainfall, which has led to new insights on a question under debate: Are seasonal changes in plant growth more limited by lack of sunlight or lack of water?

The Amazon basin, which consists of grasslands, evergreen forest, and deciduous forest where trees lose their leaves annually, has a wet season and a dry season. Past measurements from satellites have shown either no changes in greening between seasons or increased greening through the end of the dry season, attributed to fewer clouds blocking sunlight from reaching the ground. Measurements from a handful of field stations across the basin, however, indicated the vegetation greenness due to increased sunlight in the dry season would decline once the water in the soils was used up -- especially in drought years.

"Our study has helped confirm field-based results across large areas from space," Hilker said. "With our work, we have shown that there is a dry season greening but that under extended drought we get a decline in vegetation greenness."

During the dry season of an average year, the evergreen plants tap into groundwater, bask in the sunlight, and become greener.

"They're deeply rooted so they have plenty of water and they have lots of leaves," said Compton Tucker, a senior research scientist at Goddard who also contributed to the paper. "However, when you come up to one of these really dry periods, [like the drought of 2005 or 2010], then there isn't enough water to take advantage of all the light during the dry season." Water becomes the limiting factor whose effects can carry over from one year into the next if trees and vegetation die off.

Source:  NASA/Goddard Space Flight Center